Trouble with A/C

[03CL55AMG]

my 87 conquest is giving me a few problems with the AC, most notably, the compressor seems to be kicking in and out rapidly. But I’m not getting anything out of the vents. The fan is working , I did the normal things checked the Freon level, it was good, was thinking possibly relays, or high low pressure switch, which the Freon level was up near the maximum on the recharge gauge. Any ideas would be helpful thank you.

[BKB94]

What’s (GOOD ) list actual high / low pressures along with outside temp. 

[03CL55AMG]

Will do….probably be tomorrow.

[03CL55AMG]

Ok, I finally had time to check the pressures on the AC system. Temperature outside was about 80°, the pressure initially was about 60 pounds, which is in the red on the gauge. So I bled off a little bit of pressure, perhaps a little too much. But the clutch did  engage  continuously. I actually bled it down to about 15 pounds, which is below the 25 to 50 that it shows on the gauge (the green area) that I’m using. Since the pressure was below the recommended green area on the gauge, I added some more Freon. The clutch started going in and out rapidly again. And that pressure was about 30 pounds. I did notice, that the fan is not working. I don’t know if that’s because the AC is not working. Not positive on that. As always appreciate everybody’s help on here.

[BlueCuda]

My factory relay worked but it was weak, it had trouble like you mention.  I used it to trigger a better aftermarket relay and my problems went away.

 

[03CL55AMG]

I think I will check the relays….thanks

[03CL55AMG]

Hey Blue Cuda, Would you happen to have any information on where you purchased an aftermarket relay for your AC system. If you call just the normal places, Auto Zone, Pep Boys, O’Reilly’s. They really can’t find anything or narrow it down much.

[BlueCuda]

I said aftermarket but should have probably said generic.  I just used a standard 30 amp relay.  I wired it to the battery for power and used output of the factory relay to trigger it.  The only load on the factory relay is the coil of the added relay.  It fixed the problem with the clutch kicking in and out.  

[03CL55AMG]

Very ingenious, I appreciate the tip. That’s probably what I will try to do then.

[03CL55AMG]

So , I replaced the magnetic clutch relay and the compressor clutch….engaged for maybe 10 min. While it was engaged, I checked the Freon pressure….it was in the low range…a little below where it should be…15psi ,So I added some Freon to bring it up into the normal range, then the clutch started engaging  and disengaging rapidly again. Not sure why this is. Any ideas that anybody would have would be helpful. I did let off a little bit of Freon after that but the compressor clutch was still engaging and dis engaging rapidly.

[BKB94]

I think it’s time to take it to a shop or get gauges that read high and low. Could be that you are hitting high pressure switch or that switch is defective. AC systems are pretty stupid. Your HVAC control send power to the relay and that goes through two pressure switches up front right off the dryer. If both switches are happy the clutch gets power and spins. Under or over pressure opens a switch and compressor shuts off.  You could check for voltage at the switches when the clutch is cycling or feel the switches and should know if it’s the high or low killing the clutch. Make sure the condenser fan is on and add an extra fan while idling in front of the car. Open doors with AC on max. 

[03CL55AMG]

Thanks BKB94…..I will try that next.