[scarecrow1f9]

I got my AC hooked back up today and the performance is.... well, lackluster to say the least. I've never had a classic car with AC before, so I'm not sure what to expect.

I had someone hook it up for me, AC work is a bit beyond me. He explained that the sensor (somewhere behind the glovebox area) had a short, he could not get it to work. He manually set up a toggle switch to control the compressor until I could get a replacement part. Ghetto, yes, but it gives me an opportunity to test it.

With the compressor on, charged, running at max - I get a strong gust of air that is very slightly cooler than the air temp outside in the 90's. It does not seem to get any cooler regardless of engine rev or time left on.

If the AC's in general don't run much better than this, there's really no use in me going through the work of replacing the hard-to-get to parts.

Would bypassing the module that controls the clutch function of the compressor and manually controlling it affect the temperature the unit blew at all? Is there another piece besides the compressor I should swap - since the compressor itself tests fine and the system holds pressure?

As usual thanks very much for the help guys

 

[desertdave55]

If everything is working properly, a classic car with AC will blow plenty of cold air. With the compressor hard-wired like you describe, you should be getting cold air. I'd recommend using that toggle switch only for testing at one-minute intervals to avoid damaging components (or blowing them up). Some questions for you:
-What type of Freon was used? (R134a or R12)
-Was the system properly evacuated before the new freon was put in? (basically using a vacuum pump to suck out all the moisture in the AC lines..also a good way to check for leaks)
-Was a new receiver/dryer/filter installed before the new freon was put in?
-At the compressor, does the smaller diameter pipe get kinda hot, while the larger diameter pipe gets cool/cold?
-Has anyone hooked up gauges to your AC system to monitor the high and low pressures?

Your answers to these questions will be really helpful in diagnosing your AC problem.

 

[leonbray]

I have all my a/c set up with a separate on/off switch. It is wired in the a/c compressor circuit from fan switch => a/c switch => condensor temperature sensor => receiver dryer pressure switch => compressor

The only sensor is the one that cuts out the compressor if the condensor has frozen up. That can be bypassed easily at the sensor with a simple jumper.

R134 in a standard condensor will not work as well as R12 but it should still cool the vehicle with a very cold air flow

You also need to make sure the heater isn't on and mixing in hot air. What is the air temperature from the vent without the compressor running?

BTW - are you sure the compressor is running?

 

[Cedar Rapids Ia]

What year of car? Also, do you have the heater hose valve closed to the heater core??

 

[Bad69cat]

I'm no expert on the AC stuff either Jay - but I think there is a special do-hickey (technical term!) that should be inline on your heater hose run that shuts off the heater core flow when the AC switch is on. I seem to recall seeing one on a car that had AC anyways....

 

[Cedar Rapids Ia]

I'm no expert on the AC stuff either Jay - but I think there is a special do-hickey (technical term!) that should be inline on your heater hose run that shuts off the heater core flow when the AC switch is on. I seem to recall seeing one on a car that had AC anyways....

Mike, yeah I know what you are talking about ( it is vacuum operated I think) mine is a manual valve...open the hood and turn the valve to shut it off. I know in the summer if I don't close that, my air conditioning never really gets cold, once it is closed....Brrrrrrrrrrrrrrrrrrrrrrrrrrrr, I did have the R134 in it and pumped that back out and replaced it with R12.

 

[jcbingcougar]

I'm no AC expert but I do know that a properly functioning system will freeze you out of the car. I've converted mine from R-12 to R-134A and I can't have the blower on high for more than 15 minutes or I'll be freezing. Are you using R-12 or R 134? If R-134, did you replace the evaporator, condensor, drier or hoses? People say the 134 doesn't blow as cold but if the system is properly designed and the components correct for the type of refrigerant used, it will work great.

 

[Local Hero]

I did have the R134 in it and pumped that back out and replaced it with R12.

You must be independently wealthy. :1poke:

 

[Bad69cat]

You must be independently wealthy. :1poke:

LOL - True that!! Even at the auction house the guys are gloming onto that liquid gold!!

 

[Cedar Rapids Ia]

You must be independently wealthy. :1poke:

Well...um....er....oh what the he!!, no I have a good friend that is an HVAC installer and he works for beer.

 

[Bad69cat]

OK - I just realized my wiring diagram is laying right here since I was copying stuff for someone. Here's the basics of the AC system: you have heater/blower switch, AC mode switch, AC De-icing switch (is he saying that is shorted I wonder?), compressor clutch solenoid, blower motor resistor box, blower motor, and of course the fuse panel/ignition switch. I dont' see any pressure switches or anything, so I can't imagine anything to sinister is involved. It's a 20A feeder from th fuse pannel to the heater/blower switch, (high/medium/low), to the AC mode switch / the resistor box and to the motor (motor is grounded), From the AC mode switch to the De-icing switch, throught another cable assy to the AC clutch.

It would be aweful easy for a switch to look like a short if it is in fact "on" (ie not open), but I don't know what accuates the de-icing switch?.....

For the non-cool part of it - ya got me? Pull it down again, run a cleaner through perhaps? IDK

 

[smag60]

Get someone with A/C gauges who know how to use them. There is an A/C performance test you can run. If your line pressures are correct and your heater control valve is functioning you should get cold air from the vents. I had a compressor fail internally and even though the system was charged the pressures in the A/C lines was equal. You should have a low and high side otherwise the system has equalized. Also when the system was reconnected was it evacuated properly? Was the receiver /dryer replaced along with the expansion valve?