AC Not Working - HELP?

[vesnyder]

Anybody out there give me an idea how to debug my AC? I assume it is the swicth, but sure would love to be able to confirm. It worked most of the day today, but then it just stopped. It was working intermittently for a short while, which makes me think it is not a fuse. Is there a relay I should check? It is really hot and humid here and it was blowing nice and cold before it crapped out!!

[scottb]

Vance: If you have a low pressure cut-off switch (a common upgrade when replacing hoses), and a leak, the compressor won't kick on.

[bigchillcar]

mine will periodically do this while running the a/c fan motor on high speed..in my case, i think it's a matter of momentarily reaching the limit on my alternator because my stereo will sometimes quit for a moment until i turn the volume (power) down and then it continues.
ryan

[vesnyder]

Thanks for the ideas. I do not think it is the alternator, because I had my stereo totally disconnected (returning from DE event).

It appears to be some sort of cut-off switch, but it is entirely stock, including hoses - is there some low-pressure cut-off I should check?

[jdowty3]

Is the compressor clutch clicking off? There are several relays in the system. My 83 did not have any pressure switches unitl I added them so I don't think your will either.
The 3 possible culprits are the relay in the smugglers box by the condensor, the tempostat in the passenger footwell or a problem with the thermoswitch that runs from the console to the condensor.
I have just started having a similar problem and noticed that my compressor is getting voltage but not enough to engage the clutch. I paln to do more troubleshooting next weekend.

[vesnyder]

Jim - Thanks for the info, and provide me updates as you debug - sounds like the same issue. The compressor clutch is not engaging. It all started when I placed a light into the switch to see if it is on or not? I iwll check the three culprits you outlined and will let you know if I find anything.

[DonMo]

I also had the fan switch fail on mine that caused an intermittent problem. Once I opened up the console and moved the wire, it came on. Check it soon, it gets real hot with a problem switch.

[ruf-porsche]

The compressor clutch is not engaging, but is the blower fan for the evaporator coming on? If not it's a relay. Probably the relay in the smuggler box. For a quick cheap fix, you can buy a relay that will fit the relay socket at Rat Shack. The relay is also a lot cheaper than a POSCHE relay which are now made in CHINA.

[kuehl]

Assuming the clutch is not engaging and you probably don't have low/high pressure switch feature as it was not stock:

1) Turn the key on, don't need to start the engine.

2) Turn the left, thermostat, console switch knob to max cold.
Turn the, fan speed, console switch to any fan speed, 1-3.

3) Locate the clutch coil connector, near oil filter, female and male spade terminals usually in translucent rectangular cover. Unplug them. Using either a check light to ground or or a volt meter, check for voltage from the male spade connector by the oil filter. If you have voltage, then use an ohm meter to check the resistance of the clutch coil, check resistance between female spade terminal at clutch and compressor ground, should be around 3.0 ohms nominal, if no resistance or less than 2.25 ohms then your coil wire inside the clutch coil broke or near grounding, if you got a circuit then you have a grounded coil. Most coils fail due to overheating of the compressor (we'll discuss another time).

4) If you don't have any current at the male spade connector by the oil filter then check your ac fuse,
what is it ? # 3 position (you can look that up).

5) If fuse is OK, then you want to check the thermostatic switch, especially since you said something about working with wires. If the aluminum tube from the left hand switch in the center console leading to the evaporator snapped, the gas escapes the tube, yada yada yada, and won't allow the circuit to complete. Open the center console and locate the two wires connecting to the left hand switch. With the key on and right hand knob turned to fan speed 1,2 or 3, cheat a little here and jump the two female spades on the back of the thermostatic switch listen to hear if the clutch makes and breaks.
We'll stop here for the moment.

Originally posted by vesnyder
Jim - Thanks for the info, and provide me updates as you debug - sounds like the same issue. The compressor clutch is not engaging. It all started when I placed a light into the switch to see if it is on or not? I iwll check the three culprits you outlined and will let you know if I find anything.

[vesnyder]

Kuehl - Thanks for the detailed steps, will be very useful when I dig in. What do you do if the "coil wire inside the clutch coil broke or near grounding"? Can it be repaired?

Already checked the fuses, so that does not appear to be the problem.

Is it safe to bypass the thermostatic switch permanently? I found a fellow Pelican that I am getting a replacement 3-way fan switch from - is failure of these common?

I am travelling but will dig in ASAP and will let you know how I fare.

Thanks again.

[jdowty3]

The purpose of the thermoswitch is to shut off the compressor if the evaporator freezes. I don't know if having the compressor continue to run would cause system damage or not. The main problem with the evaporator freezing is that the air is forced around it rather than through it.

[JackT]

I had the same problem. Fan stopped running. I pulled the fuse for the fan and filed the ends just a little, put the fuse back in and the fan has worked great ever since. Probably now that I am bragging about this, it will not work tomorrow.

[kuehl]

If you got time and lots of beer, we can fix anything.
But it would be wiser to replace compressor and clutch coil.
However don't worry about that yet until you check it out.

I love fuses.

Never bypass the thermostat it serves two functions:
cockpit temperature control (who needs it....hmmm),
evaporator icing. ... prevents it as posted.

Fan speed switches do fail from time and current,
the load for the fan is carried through the switch and the resistors in RH intake.

Enjoy your travels.


What do you do if the "coil wire inside the clutch coil broke or near grounding"? Can it be repaired?


Already checked the fuses, so that does not appear to be the problem.

Is it safe to bypass the thermostatic switch permanently? I found a fellow Pelican that I am getting a replacement 3-way fan switch from - is failure of these common?

I am travelling but will dig in ASAP and will let you know how I fare.

Thanks again.

[vesnyder]

Kuehl-Went throught your debug process and it appears I am not getting curent to teh compressor? Opened the console and checked the switches. I am getting current to the fan switch and checked the swicth via an ohmeter and it appears to be working correctly. I also tried jumping thermostatic switch and still no current at the compressor? I also tried bypassing the fan switch andstill no luch? Any other ideas? I assume since I am getting current to the switch that the fuse and the relay are working fine? Is there something between the switch and the compressor that may be prohibiting the current of getting to the compressor?

Thanks for your help

[kuehl]

I wonder if you had current at the thermostatic switch?
One nice thing about Pelican's site is the schematics on-line,
you don't have to worry about dog eared padges!
Check out the schematic for the AC here
http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_AC.jpg
use this now to verify the thermostat and the trace the current
flow backwards (i.e. current at the switch, current at the relay, etc).

[vesnyder]

I have the electrical schematics - will have to check the voltage at the thermo switch. Thanks - another thing to try! Stay tuned.

[vesnyder]

I do not have current at the thermoswitch? Which relay should I check? I changed the one noted tempostat (??) in the front and another in the rear marked cooler fan - which one is it? Neither one made a difference. All the fuses seem to be OK - is there one I should check? I changed the AC fuse and it did nothing?

[kuehl]

Check resistance at thermostat control (left hand control in center console) using ohm meter: Remove the wires from back of the thermostat control. Check resistance of switch between the two female spades on the back of the control with the switch in the on and off positions.

[ruf-porsche]

Originally posted by vesnyder
I do not have current at the thermoswitch? Which relay should I check? I changed the one noted tempostat (??) in the front and another in the rear marked cooler fan - which one is it? Neither one made a difference. All the fuses seem to be OK - is there one I should check? I changed the AC fuse and it did nothing?

Relay for the a/c is in the smuggler box next to the evaporator.

Go to Rat Shack and purchase an automotive relay for 5 bucks.

[Brillo]

Look closely at the fuse terminals. Are they tight or loose?

In my SC I had the fan for the A/C go intermittent. Fuse was fine, but upon closer examination, I found that the terminals had degraded from the heat and had become permenatly loose. I replaced that portion of the fuse block. Luckily it was a small section of the block.