Aaron R.

I have posted on this problem before but have still been unable to solve the problem.

Fan still will not kick on automatically. Always used to come on right at 220*. Now it does not come on at all, unless I ground the wire running to the fan coolant sensor. Obviously since I can ground the sensor wire and have the fan come on means the fan works right, and it seems to indicate all my wiring is fine too. Everything points to the sensor, but I have tried 2 brand new sensors (Kragen & Autozone) and one used sensor (plus the original one which only had about 5k miles on it), and still the fan will not kick on automatically. I have tried removing some coolant and refilling it case it had some kind of freak air pocket and I have checked all fuses and obvious wiring.
I have no idea what else it could be, and surely 2 new sensors would not be bad. I am not interested in wiring in anything not stock or any hillbilly engineering. I want it to work like it was designed, but I can't seem to fix it.

2_point8_boy

Does the fan come on when you turn on the A/C? Assuming the A/C works of course.

John in RI

iTrader: (167)

How about the fan relay mounted on the drivers side of the engine firewall ???? Those things are notorious for failing.

mvftw

iTrader: (1)

The relay is by the brake booster in the corner. There are 2 or 3 relays. Search here for a picture & location...

Aaron R.

A/C is hooked up but isn't charged. Fan does not come on with a/c switch on.

I haven't replaced the relay because it seems to work fine since I can get the fan to kick on by grounding the sensor wire. I did call several auto parts stores to see about a new one and they all said they couldn't get that relay. Dealer only item???

Street Lethal

iTrader: (16)

Relay's are made up of electromagnet armature's that can be attracted by the electromagnet spring set of electrical contacts. By you grounding the sensor wire directly, you inadvertently "acted" as the relay. You performed it's job for it. This is not to say that the relay is the cause of your problem (inspecting it's internals, and/or a simple replacement will most certainly confirm this, though). Did you try the fan switch?

-Gaspar

Aaron R.

What fan switch?

rhomanski

If I'm not mistaken you should have one fan and it's controlled by the computer through the relay and because of the temp sensor.It would fail to come on if one on these doesn't work right.That's also assuming your wiring harness is complete and still good.

Street Lethal

iTrader: (16)

If you jump both the A & B terminals in the ALDL with a paperclip, and the fan immediately turns on, and yet, the fan does not immediately turn on when you switch the A/C to the 'on' position, then it's more than likely a bad fan switch, also known as an A/C pressure fan switch. Much like the Coolant Temperature Sensor (CTS), the fan switch is an information sensor for the ECM....

-Gaspar

2_point8_boy

The A/c isn't charged, so it won't come on with the A/C.

I'll have to do some more research on how the fan switch in the back of the passenger side head is wired in. None of the schematics I have here at home show it. I'll let you know what I find.

Street Lethal

iTrader: (16)

But this would depend on the ECM being utilized, as General Motors changed the trigger settings I believe (in reference to the A/C being charged or not). The A/C pressure fan switch (not the relay, which is next to cooling fan relay, and fuel pump relay on the drivers side firewall) is located on the thin aluminum tube that runs along the frame over on the passenger side....

By disconnecting this switch, the fan should immediately turn on, regardless of pressure (a fail safe). By keeping it connected, the ECM is waiting on approximately 1600 kpa before activation. If the switch is failing (but kept plugged), the fan will not turn on, as although pressure is being sensed, the trigger is flawed (again, based on which ECM is being utilized)....

-Gaspar

Aaron R.

The a/c has been discharged for as long as I have owned the car yet the fan did come on at the right time until recently. Switching the a/c to "on" has never kicked the fan on while I have owned the car.
The entire wiring harness is in original condition, so nobody has been monkeying with the wiring.
I would like to figure out exactly what the problem is before I buy any parts because I have tried fixing things before by replacing every possible problem part and it always ends up costing me big $$$ before I end up replacing the right part.

EDIT: I will try disconnecting the a/c switch today to see what happens.

Street Lethal

iTrader: (16)

Not only that, you need to jump terminals A&B in the ALDL, as if the fan does not come on doing this, it could be the ECM itself....

-Gaspar

Bullydawg

iTrader: (7)

hey... My name is Aaron R. No joke. Haha, what are the chances.

Aaron R.

cool


The fan comes on when I jump A & B. Also, I put a reman computer in the car about a year ago and everything worked exactly the same as the one it had originally so I am sure the ECM is fine.
I disconnected the a/c fan switch and the fan does not come (figured as much, since the a/c doesn't have a charge anyway).

Street Lethal

iTrader: (16)

But this is good though (in reference to jumping the A&B terminals), as it's apart of the process of elimination. Again though, depending on the ECM, some are designed to turn the fan's on when the switch is unplugged, while other's aren't (mine turns on the fan when the connector is pulled). A few threads ago I mentioned the internals of a relay. You stated that you grounded the sensor wire, and the fan immediately turned on. However, when I responded to that up above, I was implying that that doesn't mean that the relay is good. You simply did it's job for it. The relay can still be bad....

-Gaspar

2_point8_boy

Yes, but since the A/C is discharged and empty...we don't care about it anymore.

You say you've replaced the switch in the back of the passenger side head, right? I need to find a wiring diagram for you that shows exactly where that wire goes, I think it is a secondary ground for the fan relay, in parallel with the ground through the ECM, but I have to make sure for you.

Street Lethal

iTrader: (16)

^ What switch behind the passenger side head? Here is a pic of that general area, there is nothing there, aside from a system ground. The fan "switch" is the A/C pressure switch;



To the original poster, the ECM is programmed, w/Air Conditioned equipped vehicles, to kick the fan's on when 1600 kpa is realized. It's true setting though is in the 230's, and not 220. You hear the fan turn on at around 220 becasue of the A/C charge. If it's NOT charged, the fan will not kick on at 220, it'll kick on in the 230's....

On non A/C equipped vehicles, the fan is programmed to come on at a much cooler 220 (as opposed to 230). The only way to determine if your fan is not working with the A/C not charged is to bring the temperature into the 230's (which, with a system without air pockets in it, isn't so easy to reach, even with the fan off, which is why it's not being triggered). Contemplate this for a moment....

With A/C = (either when 1600-kpa is realized, or when 23X is reached)

Without A/C = (when 220 is reached)

-Gaspar

2_point8_boy

OK, I don't think you really understand how our electric fans work. The pressure switch in the A/C system is ONLY pressure, no temp of any kind.

The only place the ECM gets it's temperature reading from if the ECT in the front of the intake manifold, that's it. The only reason that the ECM controls the fan is when there si an ECM request (on 2.8L motors, not 3.1's, these are full control IIRC).

On the 2.8L motors, there is a sensor in the rear of the passenger side head, has a single wire harness connection with a green wire. That is the sensor to turn the fan on and off. It turns the fan on at 225* and off at around 200*.

Your 3.1 is different, IIRC, as the fan is 100% controlled by the ECM, no other switch. I'll take a picture of mine later today to show you.

Aaron R.

Thanks for all the suggestions guys. 2_point8_boy is correct about the fan switch, the 2.8 is different from the 3.1.

That switch (or sensor) in the rear of the head is the one I have replaced with several new ones. I would be very interested in knowing if that wire is a secondary ground. Maybe that will point me in the right direction. I have a Haynes, but it doesn't even know that sensor exists.

Street Lethal

iTrader: (16)

Never said that the A/C switch's "pressure" was based on temperature readings (how can it be), which is why the A/C pressure switch is not in the head to begin with (why do you think I keep embellishing KPA, Kilo Pascal; kilogram force per square centi-meter. kgf/cm2. pound force per square inch. lbf/in2. foot of water. meter of water, found within the A/C system's pressure lines)....

By the way, don't know why your implying that I'm getting my information from a Haynes manual, as I've never owned such a book in my entire life lol.....

No kidding. However, it is PROGRAMMED to turn on the fan's when other readings are met, including K-P-A....

Also, if the "only" place the ECM get's it's temperature reading is from the ECT/CTS in the FRONT of the intake manifold, then why would the 2.8's fan "switch" that your referring to be bolted to the BACK of the cylinder head of all places....?

^ Answer: Because the overide switch is not ECM controlled.

-Gaspar

Street Lethal

iTrader: (16)

Just to clarify something here, because it's obvious your now very content with trying to prove me wrong. Again, WHERE did I say that the A/C pressure switch is triggered via coolant temperature readings? Where? When there is not enough air flow over the A/C condenser, the A/C pressure switch TURNS ON the cooling fan (VIA THE ECM) to remove the heat. Period. If the switch fails, some (as I already stated) ECM's trigger the fan immediately as a fail safe....

-Gaspar

Street Lethal

iTrader: (16)

Thought you said that you replaced the CTS with several new ones in you first post?

Aaron R.

Yes, the one for the fan, which is often referred to as the fan coolant sensor. This is the sensor located in the coolant port in the passenger head. This sensor is not to be confused with the engine CTS (ETS) or the temp guage CTS.

EDIT: Not sure how I implied that other people were referencing Haynes. I simply said "I have a Haynes" and it didn't do ME any good. I have no idea what you guys use.

Street Lethal

iTrader: (16)

As already embellished though, the ECM ONLY receives coolant readings from the "engine" CTS found in the front of the intake manifold. Did you try replacing the Coolant Temperature Sensor yet? Without replacing the fan relay, or the CTS, your shooting the arrows with your bow in the dark....

-Gaspar

Street Lethal

iTrader: (16)

That response of mine wasn't directed toward you....

Street Lethal

iTrader: (16)

Alright now, you guys made me dig through my old mechanic volumes. The ONLY thing that I see back there (in reference to behind the passenger side cylinder head, on these particular engines), is a non ECM controlled fan OVERIDE switch. Is this the switch that your all referring to, because provided everything else in the system is okay, and after examining the schematics, I don't see how this switch would stop the fan from turning on if it happened to go bad....

-Gaspar

Street Lethal

iTrader: (16)

^ The fan overide switch is not ECM connected, and since you've tried replacing it three times, it's more than likely not the problem. Try to pick up a new CTS from Autozone, as well as a coolant fan relay. This seems to point to where the real problem lies...

-Gaspar

Aaron R.

That should be the same switch I have been referring to. Strangely enough, I had this problem once before and replacing that switch fixed it. I have been under the assumption that this sensor is a ground that closes the circuit at about *220, thereby grounding the fan through the block and causing it to come on, then somewhere below *220 the circuit opens and the fan turns off. However, I am not sure how that affects or interacts with the fan relay since I don't have a good wiring diagram.

I just called Autozone and the guy I talked to this time said they DO have that relay, in stock for 8.99. I must be having some bad luck there because a few weeks ago I called Autozone and Kragen and both told me they couldn't get that relay.
I guess tonight I will go out and buy the relay and a new engine CTS since they are pretty cheap. I will let you guys know what happens.

Street Lethal

iTrader: (16)

One of the best way's to determine the authority (so to speak) of that fan overside switch would be to disconnect this switch, then jump both the A & B terminals again over by the ALDL, and see if the fan turns on. If it does turn on, then the fan can obviously be controlled without that switch. If it doesn't turn on, then it has more authority over fan control than expected....

That fan overide switch is basically the same switch in which the aftermarket electric fans come with (for non ECM applications). I honestly don't see how a failed overide switch will stop the fan from kicking on through the ECM, but again, the best way to double check (for the sake of conversation), would be to jump A & B with that overide switch disconnected, to see if the ECM is at the mercy (fan wise) of that switch....

But yeah, get a new CTS and relay, and see what happens once installed. If it still doesn't work, you need to start tracing the wire's back, and checking each and every ground. ECM is obviously good, fan turns on so it's good, your replacing the CTS and the fan relay, and you've already replaced the overide switch quite a few times. If it still doesn't work, it has to be somewhere in the wiring (possibly a pulled connector terminal, or bad ground, etc.)....

-Gaspar

RBob

iTrader: (1)

This is from the '87 FSM. Hope it helps. As an aside I have no idea if the ECM controls the fan via CTS, or just from the A/C pressure switch and diag mode.

RBob.

2_point8_boy

OK, I think we are at a point of misunderstanding. First off, I never mentioned anything about a haynes manual. Not a single word about it.

Second, the A/C pressure switch is, in fact, not designed to help with cooling the engine coolant, but is actually there to turn on the to pull heat OUT of the CONDENSER when you're at an idle. Tha'ts why it comes on even with a cold motor when you turn on the A/C.

It's not that I am bent on proving you wrong, it's just that you're kind of going in the wrong direction. Since the A/C doesn't work to begine with, we no longer care about the fact that the A/C pressure switch is even in the picture.

Exactly, the fan switch is not ECM controlled, but grounds the fan relay independently of the ECM in case of signal failure to the relay. This is something that I am not arguing.

What I'm saying is that we need to stop even thinking about the A/C system since it is inop. I agree with you that a failed override switch shouldn't keep the fan from working, since it is wired in parallel with the ECM ground signal to the relay.

Everything else aside, here's how you cehck the system operation:

1) Connect terminals A & B and turn the ignition to "on." The Fan should start if the ECM is able to controll the relay, the relay functions, the circuit is complete, and the fan itself is operational. If this doesn't work, you'll have to break out a test light to see where there is and isn't power.

2) Disconnect the override switch in the back of the head. Use a jumper wire to connect it directly to ground. The fan should come on. Reconnect sensor wire. This checks the wire from the sensor to the realy activation ground circuit.

3) If Fan comes on in step 1, then the ECM is ABLE to control the fan correctly. If it comes on in step 2, then the override swtich is ABLE to control the fan correctly. If it comes on in either case, the power to the relay is good, the power to the fan is good, the ground to the fan is good, and the ground control circuit being tested is good.

4) If the fan does not operate in step 2, there is a break in the ground control circuit from the relay to the override switch. If the fan does not operate in step 1, there is a break in the ground control wire going back to the ECM -or- the ECM itself is bad because of a blown fan relay driver.

If the fan doesn't operate at all, then you need to get a test light and start checking for power and ground at various points in the circuit.

From what I found out today, I did in fact find that the ONLY time the ECM activates the fan in a 2.8L F-Body, is when there is a successful A/C request (meaning that the ECM only turns the fan on when the compressor pumps enough pressure into the high side of the A/C system that the ECM thinks the A/C is running.) That's it, ECM control ONLY with working A/C.

So, Aaron R., it from what you describe, it looks like the fan is good, the relay is good (since the fan comes on with A/B terminals connected), and the power to the relay/fan is good. I would tell you that you have a bad wire from the temp sensor in the back of the head to the ground control for the relay. perform test #2 to confirm.

Street Lethal: no need to get defensive, I don't have anything against you, it's just that if he's chasing down "bad" switches in the A/C system, he'll never get his fan to work.
----------
OK, I think we are at a point of misunderstanding. First off, I never mentioned anything about a haynes manual. Not a single word about it.

Second, the A/C pressure switch is, in fact, not designed to help with cooling the engine coolant, but is actually there to turn on the to pull heat OUT of the CONDENSER when you're at an idle. Tha'ts why it comes on even with a cold motor when you turn on the A/C.

It's not that I am bent on proving you wrong, it's just that you're kind of going in the wrong direction. Since the A/C doesn't work to begine with, we no longer care about the fact that the A/C pressure switch is even in the picture.

Exactly, the fan switch is not ECM controlled, but grounds the fan relay independently of the ECM in case of signal failure to the relay. This is something that I am not arguing.

What I'm saying is that we need to stop even thinking about the A/C system since it is inop. I agree with you that a failed override switch shouldn't keep the fan from working, since it is wired in parallel with the ECM ground signal to the relay.

Everything else aside, here's how you cehck the system operation:

1) Connect terminals A & B and turn the ignition to "on." The Fan should start if the ECM is able to controll the relay, the relay functions, the circuit is complete, and the fan itself is operational. If this doesn't work, you'll have to break out a test light to see where there is and isn't power.

2) Disconnect the override switch in the back of the head. Use a jumper wire to connect it directly to ground. The fan should come on. Reconnect sensor wire. This checks the wire from the sensor to the realy activation ground circuit.

3) If Fan comes on in step 1, then the ECM is ABLE to control the fan correctly. If it comes on in step 2, then the override swtich is ABLE to control the fan correctly. If it comes on in either case, the power to the relay is good, the power to the fan is good, the ground to the fan is good, and the ground control circuit being tested is good.

4) If the fan does not operate in step 2, there is a break in the ground control circuit from the relay to the override switch. If the fan does not operate in step 1, there is a break in the ground control wire going back to the ECM -or- the ECM itself is bad because of a blown fan relay driver.

If the fan doesn't operate at all, then you need to get a test light and start checking for power and ground at various points in the circuit.

From what I found out today, I did in fact find that the ONLY time the ECM activates the fan in a 2.8L F-Body, is when there is a successful A/C request (meaning that the ECM only turns the fan on when the compressor pumps enough pressure into the high side of the A/C system that the ECM thinks the A/C is running.) That's it, ECM control ONLY with working A/C.

So, Aaron R., it from what you describe, it looks like the fan is good, the relay is good (since the fan comes on with A/B terminals connected), and the power to the relay/fan is good. I would tell you that you have a bad wire from the temp sensor in the back of the head to the ground control for the relay. perform test #2 to confirm.

Street Lethal: no need to get defensive, I don't have anything against you, it's just that if he's chasing down "bad" switches in the A/C system, he'll never get his fan to work. Thank
----------
OK, I think we are at a point of misunderstanding. First off, I never mentioned anything about a haynes manual. Not a single word about it.

Second, the A/C pressure switch is, in fact, not designed to help with cooling the engine coolant, but is actually there to turn on the to pull heat OUT of the CONDENSER when you're at an idle. Tha'ts why it comes on even with a cold motor when you turn on the A/C.

It's not that I am bent on proving you wrong, it's just that you're kind of going in the wrong direction. Since the A/C doesn't work to begine with, we no longer care about the fact that the A/C pressure switch is even in the picture.

Exactly, the fan switch is not ECM controlled, but grounds the fan relay independently of the ECM in case of signal failure to the relay. This is something that I am not arguing.

What I'm saying is that we need to stop even thinking about the A/C system since it is inop. I agree with you that a failed override switch shouldn't keep the fan from working, since it is wired in parallel with the ECM ground signal to the relay.

Everything else aside, here's how you cehck the system operation:

1) Connect terminals A & B and turn the ignition to "on." The Fan should start if the ECM is able to controll the relay, the relay functions, the circuit is complete, and the fan itself is operational. If this doesn't work, you'll have to break out a test light to see where there is and isn't power.

2) Disconnect the override switch in the back of the head. Use a jumper wire to connect it directly to ground. The fan should come on. Reconnect sensor wire. This checks the wire from the sensor to the realy activation ground circuit.

3) If Fan comes on in step 1, then the ECM is ABLE to control the fan correctly. If it comes on in step 2, then the override swtich is ABLE to control the fan correctly. If it comes on in either case, the power to the relay is good, the power to the fan is good, the ground to the fan is good, and the ground control circuit being tested is good.

4) If the fan does not operate in step 2, there is a break in the ground control circuit from the relay to the override switch. If the fan does not operate in step 1, there is a break in the ground control wire going back to the ECM -or- the ECM itself is bad because of a blown fan relay driver.

If the fan doesn't operate at all, then you need to get a test light and start checking for power and ground at various points in the circuit.

From what I found out today, I did in fact find that the ONLY time the ECM activates the fan in a 2.8L F-Body, is when there is a successful A/C request (meaning that the ECM only turns the fan on when the compressor pumps enough pressure into the high side of the A/C system that the ECM thinks the A/C is running.) That's it, ECM control ONLY with working A/C.

So, Aaron R., it from what you describe, it looks like the fan is good, the relay is good (since the fan comes on with A/B terminals connected), and the power to the relay/fan is good. I would tell you that you have a bad wire from the temp sensor in the back of the head to the ground control for the relay. perform test #2 to confirm.

Street Lethal: no need to get defensive, I don't have anything against you, it's just that if he's chasing down "bad" switches in the A/C system, he'll never get his fan to work. Thank you

2_point8_boy

OK, I think we are at a point of misunderstanding. First off, I never mentioned anything about a haynes manual. Not a single word about it.

Second, the A/C pressure switch is, in fact, not designed to help with cooling the engine coolant, but is actually there to turn on the to pull heat OUT of the CONDENSER when you're at an idle. Tha'ts why it comes on even with a cold motor when you turn on the A/C.

It's not that I am bent on proving you wrong, it's just that you're kind of going in the wrong direction. Since the A/C doesn't work to begine with, we no longer care about the fact that the A/C pressure switch is even in the picture.

Exactly, the fan switch is not ECM controlled, but grounds the fan relay independently of the ECM in case of signal failure to the relay. This is something that I am not arguing.

What I'm saying is that we need to stop even thinking about the A/C system since it is inop. I agree with you that a failed override switch shouldn't keep the fan from working, since it is wired in parallel with the ECM ground signal to the relay.

Everything else aside, here's how you cehck the system operation:

1) Connect terminals A & B and turn the ignition to "on." The Fan should start if the ECM is able to controll the relay, the relay functions, the circuit is complete, and the fan itself is operational. If this doesn't work, you'll have to break out a test light to see where there is and isn't power.

2) Disconnect the override switch in the back of the head. Use a jumper wire to connect it directly to ground. The fan should come on. Reconnect sensor wire. This checks the wire from the sensor to the realy activation ground circuit.

3) If Fan comes on in step 1, then the ECM is ABLE to control the fan correctly. If it comes on in step 2, then the override swtich is ABLE to control the fan correctly. If it comes on in either case, the power to the relay is good, the power to the fan is good, the ground to the fan is good, and the ground control circuit being tested is good.

4) If the fan does not operate in step 2, there is a break in the ground control circuit from the relay to the override switch. If the fan does not operate in step 1, there is a break in the ground control wire going back to the ECM -or- the ECM itself is bad because of a blown fan relay driver.

If the fan doesn't operate at all, then you need to get a test light and start checking for power and ground at various points in the circuit.

From what I found out today, I did in fact find that the ONLY time the ECM activates the fan in a 2.8L F-Body, is when there is a successful A/C request (meaning that the ECM only turns the fan on when the compressor pumps enough pressure into the high side of the A/C system that the ECM thinks the A/C is running.) That's it, ECM control ONLY with working A/C.

So, Aaron R., it from what you describe, it looks like the fan is good, the relay is good (since the fan comes on with A/B terminals connected), and the power to the relay/fan is good. I would tell you that you have a bad wire from the temp sensor in the back of the head to the ground control for the relay. perform test #2 to confirm.

Street Lethal: no need to get defensive, I simply just misunderstood what you had written. It just looked to me like you had temp readings and pressure readings grouped together like they were sensed off the same sensor.

Aaron R.

The fan WILL turn on when I ground the "fan override switch" wire, and WILL also turn on when I ground terminals A&B of the ALDL.

This is one reason why this problem has been so frustrating to me, because everything I check seems to work fine. But I am getting desperate, so...
I put in a new relay and engine CTS last night. Not surprisingly, this did not fix the problem. Oh well, at least those are definitely eliminated as problems. I did find something interesting (see attached). The pic isn't very clear, but some of the wires are bare, maybe pulled out some from the fan relay connector. I doubt this is causing me problems, but I will clean up the connector today and get a better idea of what it looks like.

ibmtech

iTrader: (1)

Incorrect.. They relays that you are referring to are Fuel Pump... Maf and Maf Burnoff..

Both Fan relays are located near or between the battery and Radiator support.

rover420

no it's different on a v6 dude they don't even have burn-off relay's i don't think.

Street Lethal

iTrader: (16)

No no, we already knew that the fan would turn on when these two things were done. What I wanted you to do, was, DISCONNECT the fan overide switch entirely, THEN jump A & B at the ALDL (as an experiment). This will would tell us if the ECM is at the mercy of that switch, being that the overide switch is not ECM controlled....

As far as the new CTS and fan relay, along with the overide switch that was replaced not too long ago, everything should work just fine now. What I would like to now know, is, what temperature is the engine literally reaching when your waiting for that fan to go on? I hardly ever hear my own go on, especially since I removed the thermostat, because the engine rarely reaches such temperatures, even in this ridiculous heat. The ONLY time I'll hear my fan kick on is when idling at a very long stop light in gear, only then my coolant gauge reaches 220+. Other then that, you would think my fan is broken....

-Gaspar

ibmtech

iTrader: (1)

Sorry, didn't see that it was a 2.8 .. You are correct.

jster1963

Hi Aaron,

Sorry to open an old post but I have the exact problem, except my a/c works.

Your last post was that you were going to clean up and fix the bare wires. I have the same thing with my wires. All the wires have pulled back and have bare wire showing just like yours.

Did you fix those wires? If so, how? Did you solve the problem? If so, what fixed it?

Thanks.....jster

Aaron R.

JSTER, I did finally figure out what the problem was.
It was the fan coolant sensor, which on my car is located in the coolant port at the rear of the passenger side head. I think it is also sometimes called the "coolant fan switch". When the coolant reaches a specific temperature (220* max) the switch closes the circuit and grounds the fan relay, causing the fan to come on and cool the engine down to around 180-190*.
I had replaced this switch twice already with BRAND NEW parts, 1 from Autozone, and 1 from Kragen. Apparently, the brands that A-zone and Kragen sell (both different brands) are BOTH defective, since neither sensor ever worked. I recalled that the last working switch I had installed for the fan was from O'Reilly auto parts, so bought one from them, installed it, and bingo fan works perfectly. What are the odds that two new, different brand switches are both defective, eh?

Tookie

One thing that COULD cause a problem, is if you used teflon tape
on the threads. It can cause the sensor not to ground correctly,
and screw up the reading/operation of the sensor

jster1963

Hey Aaron,

I'm glad that fixed it. I solved my problem too (so far). My problem was the bare wires at the relay connector. They must have been touching. It did not look like it, but must have been. They probably touched intermittently.

Yesterday, I taped the bare wires, and "YESSSS" the fans worked as advertised. They initially worked the first time I checked the relays, but then stopped. I must have inadvertently separated the wires that were touching, and then they had to start touching again.

I was stuck, so I thought, "start all over with the cheap stuff first." I taped the wires as a test, and it worked. Now I am looking for a permanent fix.

Does anyone know how to correctly fix the wires whose insulators pull back from their connector, exposing bare wire?

Tookie... Great information as well. Thank you both!!!

2_point8_boy

Carefully remove the pins from their socket using a small pick, then shrink wrap the bare part of the wire. I do it all the time. Works great.

jster1963

Brilliant!!!!!!! I will give that a try.

Thank you very much.......jster

jster1963

2_point8_boy

You are THE MAN. Yesterday, I was able to repair 3 connectors. They Look and work GREAT!!!!

Thanks again.....jster