Big Matt

I'm looking for a new fan switch for my carb'd 305 engine. The one I have now turns the fans on around 240* and off around 220*. I'm looking to lower the temperature and I'm wondering what temperature I should be looking for. I found one from napa that says 204*-220* but I'm wondering if I should go lower. I've been searching all over but haven't found much info.

Here is the part from napa:

http://www.napaonline.com/Catalog/Ca...11_03727965999

Ron U.S.M.C.

Picking a switch has allot to do with your thermostat setting , here's a few that you can consider = http://www.summitracing.com/parts/JET-60600/

= http://www.summitracing.com/search/?...HYP-4028&dds=1

= http://www.summitracing.com/parts/HYP-4026/

Richboll

Here're a few more closer to home..

http://www.autozone.com/autozone/par...mString=search

drjewalton

I just bought a hypertech switch part #4028 off eBay for 40 bucks. I also installed a 180 degree thermostat. Since it has been virtually impossible for me to loosen the stock switch, and since the car seems to run cooler with the new thermostat, I have opted to not install the new fan switch. It's new in box ....I'll sell at a loss for 25 bucks plus shipping if you're interested. (part #4028 turns fan on at 200 degrees and off at 185). Let me know.

I also have a 1984 L69 305...all original stock.

DJP87Z28

Wkere is the exact location of the fan swich on the cylinder head???

SumDumbGuy

I've used different head "switches" only to have them die within a month. Check the reviews on some of those switches. It's usually 50/50. Half think they're wonderful, half have them die right away. Unless you're keeping your car completely factory, I'd look into the adjustable fan kits.
I ended up buying a Derale fan kit. http://www.summitracing.com/parts/DER-16759/ It's adjustable and probes the radiator. Seems to work great so far. I can't tell you how it is in the long run though since I haven't put too many miles on it. More than any head switch I've used though.

1988GTA500HP

I don't have a stock engine but mine is on the passenger head between the #6 and #8 plugs. You can always follow the ground wire (green/white) from the relay to find it.

midias

Here is a list of common fan switch part numbers

https://www.thirdgen.org/forums/cool...tched-pns.html

SW555
SW505
SW500
SW502

Are common numbers

I use SW555 and it comes on at 210 and off around 205 it was 10 bucks at autozone.

DJP87Z28

Thanks....

Big Matt

Thanks for all the replies guys! I sent drjewalton a PM about that fan switch. I think 185-200 is a better temp range then the one I was looking at right? Would this paired with a 180* thermostat work well or should I go for a lower stat?

Big Matt

http://www.autozone.com/autozone/par...er=103831_0_0_

Shows up here for $31.99

DJP87Z28

Problem: Replaced Fan switch & plug at cylinder head and checked fan (runs with power to it). However; the fan will not come on when the temp hits 220 or higher. Any suggestions like a fuse location or and other ideas??

midias

How are you measuring temp?

Also did you try grounding the pigtail on the switch to make sure it turned on the fan?

DJP87Z28

Fan works and I said a new switch and plug. I don't follow what you said (dense about most electical)....

midias

Yea I know you have a new switch and plug. Try grounding the plug to the body or engine and see if the fan turns on to check the circuit.

DJP87Z28

Followed your advice and the fan did turn on and work. So it looks like my brand new switch dose Not work. Will get a replacement and hope that dose the trick.

Tanks for the help.

midias

It is not uncommon for aftermarket switches to die a quick death.

As a side question are you using the factory gauge? My factory temp gauge is really inaccurate it reads about 20-30 degrees over temp.

DJP87Z28

Quick as in less than one hour. New one coming on Monday and it better work.

Using a heat gun for actual temp. But my Factory Temp gage is spot on and dose not give a high reading.

midias

I have had some DOA others last 1 month and other last 5 years. On my Honda Magna I put a new on in and it lasted 13 days went back to the stock 28 year old switch and it is still good 2 years later. i just replaced it because it was cheap and I thought it would be more reliable.

1988GTA500HP

Make sure the switch is grounding to the head. Minimal tape or even better, PTFE paste. Make sure the motor is grounded.

DJP87Z28

New switch installed but did not turn fan on. However; after driving the car with the A/ on the temp stayed at 220 Deg for hour of stop and go trrafic. This was a vast imporvrmrnt. Checked the fan and its was running, now the question. Why did the fan not operate at Idle and temp above 220 in the shop??

1988GTA500HP

Which switch did you buy? The switches have a specific on and specific off temp. For example, the switch NAPA sells for my car turns on at 224-236 degrees and off at 212 degrees. So until my car reaches 224-236, my fans won't come on. I do not run the stock switch because that is too hot for my car in my location.

If you grounded the connector for the coolant fan switch and the fan turned on then you know the fan and relay are working properly. Therefore the problem has to be in the last part of the circuit. The way the switch works is that when it hits its turn on temperature it makes contact with its outer jacket (which includes the threads that it screws in with), which is connected to the head through the threads, which is connected to the engine block which is connected to the battery ground. So that leaves 4 possible problems.

1. Bad switch - I doubt it because you tried 2 different switches
2. Poor connection between the switch and the connector - if you are using the same connector as me, which is the oval plastic one with a single center pin, this would be suspect. Mine seems to fit way to loosely for my comfort. You could test this by disconnecting the connector and running a wire from the pin on the connector to the pin on the switch. Run the car til it reaches the run on temp. If it turns the fan on then that connection is bad.
3. Poor connection between head and switch - make sure there is not too much teflon tape on the switch or it won't connect (ground) to the head.
4. Poor connection between block and battery negative - follow the cable coming from the negative battery post to the block. Make sure they are tight. If you have a multimeter, you can run a continuity test between the block and the battery negative post pretty easily.

fastgascar

So if I use an SW510 will it turn the fan on @ 210 and off @ 185?

SW510 1 Male Bullet Terminal 3/8 x 18 Open Makes 210f ±10 Opens 185

midias

Yes

Ron U.S.M.C.

I just decided to pick up one of these,and am glad I did. It works great for my application.
I like having the ability to easily set the switch to a lower/higher temperature if I want.

http://www.autozone.com/autozone/par...uestid=4665868

fastgascar

Here is another option, little pricey, but you can set it on the fly.
http://www.zirgo.com/catalog/Tempera...ature-Switches

one92rs

iTrader: (5)

this is what i and several people have used for years.

http://www.summitracing.com/parts/FLX-31165/

starts fans or fan off at 60% and then will raise it only if needed.

B4cMaro

i would suggest one thats the same as the thermostat for better cooliing . i have mine set at 195 ( factory) and 165 in the summertime.

sleeper84

iTrader: (1)

Zombie thread, but yeah. Trying to update and keep data together.

Just ordered the FS110 from NAPA. Here's their current selection:

FS110 On 224-236°F Off 212°F
FS111 On 240-252°F
FS112 On 213-229°F
FS113 On 204-220°F