SkidogP

1991 Camaro Z-28 5.7L Vin engine code 8 : A/C was working great, then it stopped blowing cold suddenly. Took to buddy's shop to check pressure and for any leaks. No leaks and refill with R-134 (this was converted over from R-22 about 8 years ago). They system blew cold for about 10 minutes then stopped. I checked the compressor and the the clutch is not engaging. I started checking voltage at the clutch & compressor- Battery voltage at both connectors. I then started following wires back toward the firewall, specifically at the passenger side at the blower motor area near the firewall. The large connector (see picture) with 3 wires (black, red & blue) was very hot! So hot that when I touched the connector and black wire, it burned my finger. All 3 wires & connector were hot. I pulled the connector apart immediately to avoid it welding itself together! LOL! Now, my question is this: Could the compressor, clutch or the compressor clutch relay cause this connector or wires to heat up like this? If not, what could be causing the wire to heat up to the point of melting? Any help, testing options or ideas would be greatly appreciated. Thank you!

punkmaster98

iTrader: (5)

I would start at the hvac controls inside the car. I have personally dealt with several shorts in those units.

sofakingdom

iTrader: (1)

That connector ALWAYS gets hot. It's one of the worst-designed connectors in the entire world history of connectors. Hell I bet THE VERY FIRST CONNECTOR EVAH was better than that one. It's almost like some Stimpy at GM DELIBERATELY TRIED to come up with the WORST POSSIBLE connector they could, like they were mad at their boss or something. Nobody could come up with something THAT BAD just by acident.

The red wire is the battery feed to the blower motor high speed. The black is also in that circuit and has just as much current flowing through it. Those 2 gets the hottest. The green is the compressor; its current draw is much lower, so it doesn't burn up near as much.

Search this forum for my userID and the phrase "burnt to ashes". I've typed it so many times, there's no point in typing it yet again. Everything you need to know is already in there.

There's another connector of the same BONEHEAD design that feeds power to the whole AC control head. Pop that out of the dash, follow the brown wire up into there, about a foot or so up the wire you'll come to it. Every bit as stuuuupid. Burns up just as much. Except, when that one fries, the whole AC system gets disabled.

SkidogP

Ok thank you for the info. I will pull the head unit this weekend and check for issues. I'll let you know if I find the problem.

SkidogP

Thanks, sofakingdom! I will look into your other threads and hopefully find the problem and a fix for this.

SkidogP

I have tested most of the switches and components on the A/C system. Everything tested good so far. The A/C actually works, clutch is engaging & cold air blows out. Black wire still getting HOT.
.Prior to testing the pressure cycling switch (on the accumulator) I tapped on the switch with a screwdriver and the clutch engaged on the compressor. The car was running with the A/C set to "Norm" on high speed. Air blows cold and cycles as it should. The issue is the black wire in the black connector on passeger side (see pics) keeps getting hot to touch. I ran multiple tests with engine running & control head set to "Norm" & temp on "Cold": .
Test 1: Blower speed on "Low" - Black wire does not get hot; system seems to run great.
Test 2: Blower speed set to position 2 (One speed higher than low) - black wire does not get hot.
Test 3: Blower speed set to position 3 (One speed below HIGH) - black wire starts to get warm but took several minutes to feel warm (all functions of A/C system still working properly)
Test 4: Blower speed set to "High" - Black wire get hot almost immediately (so hot that it cannot be touched).
When I change the blower speed to "Low" or postion 2 on the head unit, the black wire cools down within 2 minutes.

When I tested the light green wire on the pressure cycling switch for voltage (unplugged from the switch, key on, engine not running), I noticed the voltage changed based on the speed setting at the head unit. (see pics). Could the pressure cycling switch be faulty? If so, why was the voltage changing while it was uplugged?
Could this be an issue with the head unit, the blower motor or the blower high speed relay? Or the A/C pressure control relay? Or is this a completely different issue? I need HELP!! LOL!

Does anyone know where the A/C pressure control relay is located? I have found threads with several different locations but the wiring diagram states the wires should be pink/black and light green/black. I cannot find a relay with these wire colors. I am looking at the 3 relays under the hood @ the firewall on driver side by the brake booster (see pics).

sofakingdom

iTrader: (1)

Again:

The red & black wires handle blower motor current ONLY. The black one has current in it in ALL blower speeds but the red wire is for high speed ONLY. You're wasting your time dinking with the compressor circuit because it's NOT The Problem. Anything you see happening on it is only a SYMPTOM of a Problem elsewhere.

As detailed in all the other threads I've typed up on this subject, that connector needs to be ELIMINATED, at least for the red & black wires. The green wire doesn't carry enough current for it to burn up the way the others do, if the housing isn't already melted and burnt all around it. It wouldn't hurt to do the same for it as well but isn't as essential as the other 2, since it only carries about 5 amps or so. Replace it with something that can handle the power (look for something rated for AT LEAST 30 amps). I've shown pics of what I've used in the past and described it in detail; you could also use something like a larger series of Aptiv or Deutsch sealed connectors as well, if you have the ability to install them.

Most likely the reason for the voltage change you describe is the burned-up connector of the same STUUUUUUPID design in the power feed to the AC control head. Remove the control head from the dash and follow the brown wire up into the weeds up there, where it plugs into the car's main harness, to get power for the ENTIRE HVAC system (except for the blower motor high-speed battery feed, which is that red wire in the connector that gets hot). Replace it as well with something that can handle higher power. It only ever sees about 10 - 12 amps or so, so a 15 or 20 amp connector system of proper design would be adequate.

I don't know of any "AC relay" in any of these cars butt maybe there is one and maybe if there is that's it. If you tell us what color the wires are maybe we'd be able to identify it. Probably isn't anything wrong with it in any case since "volts good" all through the compressor circuit.

SkidogP

Sofakingdom, Thank you for the knowledge on the connector issues!!! I finally found the post where you had explained this situation in detail. ( The post started by 92White25th on 7-13-2014)
I pulled the radio & heater-A/C head unit out and located the brown wire coming from the head unit. I found the gray connector on the brown wire- sure enough, it was also getting warm to touch. I cut the gray connector out and installed the heavy duty insulated wire connectors (male to female). I also did the same procedure on the black connector located near the blower motor on passenger side in the engine bay. On this connector, I only cut the black wire out of the connector (since it was the only wire getting hot). Cleaned up the remaining wire connections (Red wire & Blue wire) and plugged it back together. Pictures attached.
Started the car and turned A/C to high speed on "Norm" setting (this is the setting where the wires would get hot!) - Ran the car for about 15 minutes, A/C clutch cycles normal and fans came on as expected. The wires I made repairs to -did not get hot at all. So thanks again for your knowledge on this!!

My issue now is the purple wires at the connector plugged into the blower resistors are getting hot. Pictures attached. One of the puple wires goes to the high speed blower relay, the other purple goes into the large wire harness back to the firewall. Is there a way to test the blower resistor itself? Is there a test for the high speed blower relay? Could one or both of these be causing the purple wires to heat up?

These 1st two pics are showing the connector repair (fix). The second set of pics are for the purple wires/ blower resistor getting hot.
Thank you for any advice you may have on this!


Black wire cut from connector- No more issue with black wire getting hot

Brown wire w/ gray connector behind radio & heater-A/C control head (being removed)

Gray connector removed & insulated connectors installed- No more brown wire getting hot

2 purple wires getting hot at the blower resistor

Connector and pins are clean, purple wires still getting hot.

sofakingdom

iTrader: (1)

Purple is the wire to the blower motor. The way that circuit works is, various other wires, selected by the blower speed switch, send 12V to the various resistors, which then send power to the blower (purple wire). The HS relay replaces the feeds, all/any of them, that might otherwise come from the resistors, with hard battery, delivered to the relay via the red wire; the blower thus gets the maximum possible juice without a resistor dropping the voltage.

On the next-to-highest speed the current going to the blower is in excess of 10 amps if all else is ideal. Given the weeeeeeenie overall aspect of the resistor connectors, some heat generation at that point is unavoidable. Make sure the connections are as clean and secure as possible, but beyond that, not much you can do.

You need to get that red wire outta there too, and do the same thing to it that you did to the black. Otherwise it will merely be the next one to burn up.

SkidogP

Ok, thanks for the info and quick response. I will just keep an eye on the purple wires after cleaning the contacts again. I will also remove the red wire from the connector and do same as I did with the black wire. So far, A/C is running great! Thanks again for all your help!

sofakingdom

iTrader: (1)

SkidogP

In reference to the A/C clutch not engaging: I cut the red wire from the connector and installed new connector ends. I now have the red & black wires removed from the connector and repaired. I also removed the gray connector w/ brown wire under the dashboard at the radio/ climate control head. The wires/connectors are no longer getting hot.
The compressor clutch is still not engaging intermittently. I drove the car for 2 miles after the wire repairs (at this time the A/C was blowing cold & clutch was cycling while sitting in the garage). Around 2 miles of driving, the A/C started blowing hot again. l pulled over to check the A/C clutch- it was not engaging. Tapped on the pressure cycling switch and the clutch kicks "On". Stays on while idling and when I start driving it shuts off again. I want to replace the pressure cycling switch now. The car originally had R-12 and I had it changed over to R-134 about 10 years ago when I could not find anyone with R-12.
Do I need to get a switch for R-134 or just replace with an OEM (R-12) switch? Could there be a seperate issue (more wiring/connector problems? )

Black & red wires removed from black connector

pressure cycling switch- tap on it & compressor kicks "On"

sofakingdom

iTrader: (1)

No, the pressures are basically the same so the switch is also the same.

Make sure the connector is good (terminals fit tight to the blades) before buying a new switch.

SkidogP

Confirmed the blades in the connector are clean and tight. I pushed the female ends together to make an even tighter fit when pugging into the switch. With car running & A/C selector on "Normal" and using any speed, the clutch will engage when I tap the switch. Compressor then stays "on" until I have to tap the switch again to get the compressor to shut off. I believe the switch should cycle the clutch to go on & off as pressure changes in the accumulator. It does not seem to do this.

sofakingdom

iTrader: (1)

Right: tapping is not normally a required input to its operation. Sounds like it's TU.

It doesn't really exactly "cycle" the compressor except when the ambient temp is low. It's more a "safety" device; it shuts the compressor off at a pressure of about 20 psi or so, which corresponds to about 25°F at EVP. Its purpose is to shut off the comp when the evap might be about to freeze up. Once the comp stops running, the pressure starts to rise; the switch restores at 60 psi or so. Normal operating pressure should ordinarily go no lower than 30 - 35 psi so it doesn't usually do its thing.

SkidogP

Ok, that makes sense! I will take it out for a longer drive and see if the compressor/clutch cycles. It is 90 degrees & sunny w/ 13% humidity today. Good day for a test, Thanks!