AC Compressor Issue
Thread Starter
Le Mans Master
Joined: Nov 2000
Posts: 5,689
Likes: 0
From: Cape Coral, FL 33904
AC Compressor Issue
Just started the other night, and have not had a chance to look at the car until later today. When I start the car and put the AC on, it works great, then a few min later it's like the compressor turns off and warm air comes in. If I leave everything on, it will come back on. Sounds like an electrical issue...but where should I start? The compressor is a few years old, and the system was recharged last year. I hooked up a gauge and the charge is still good. Any ideas?
Thread Starter
Le Mans Master
Joined: Nov 2000
Posts: 5,689
Likes: 0
From: Cape Coral, FL 33904
I think the clutch is slipping since it spins very slow when the AC is off. Would that make the air cold, then warm while it's running? Are there rebuild kits for the clutch?
Former Vendor
Joined: Nov 2006
Posts: 2,482
Likes: 3
From: Carmichael ca
If the clutch is spinning when the AC is off it means the clutch is dragging. There are no rebuild kits, you just replace the clutch. You need to determine what's happening when the AC quits before you start replacing parts.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
NAPA sells individual parts including a pulley bearing, but it's easier just to replace the entire unit. Check the air gap between the outer hub and pulley, should be .020 inch. Check power and ground. Some of the electronic units (through '89) always supply power so one wire would always be hot and a coil shorting to ground could make it spin or appear to slip even when off. You also need to check operating pressures.
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Former Vendor
Joined: Nov 2006
Posts: 2,482
Likes: 3
From: Carmichael ca
There are small shims, like tiny washers, behind the outer clutch plate. Remove the nut holding the plate on, you'll see the shims where the stud is. Add shims to increase gap.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
They shouldn't wear out - unless someone went to Home Depot and found replacements that looked about right (hard to blame them since the 3 or 4 measly washers in the kit are 12 Bucks). Then the cheap tin alloy gets crushed and the air gap goes away - or someone overtorques the shaft bolt and crushes the shims during installation. Anyway, on these units, it's usually the gap getting wider from wear on the face plate and pulley. Other Harrison compressors, with a press on assembly, seem to lose the gap when driven off of the Dealers Lot, but not these Nippo's with a bolt holding the face plate. I would make sure that it doesn't have a leaking shaft seal - check for oil on the hood above the compressor.
Thread Starter
Le Mans Master
Joined: Nov 2000
Posts: 5,689
Likes: 0
From: Cape Coral, FL 33904
So I finally had some time to work on this. It's just been too hot to do anything here. Anyway, changed out the clutch, and started the car. Worked great. Later that day I took the car out for the night, and it did the same thing about a mile down the road. What could this be now? Any suggestions on what to check?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
I think the reference is to the Low Pressure Switch which is mounted on the Evaporator outlet - big tube on top. It opens at 25 psi which breaks the circuit to the compressor. It's there to prevent the Evaporator from icing up and/or the compressor from running when there isn't enough gas to carry the oil charge. Whether or not it reaches the cutoff threshhold is also dependent on the outside air temp. The only viable test is with a Manifold Gage Set (preferably with an air temp above 70 degrees). That will allow you to observe the Low Side Pressure with the compressor engaged and with the system on Max, disconnecting the Blower Motor will drop the Low Side and the Compressor should cycle off at the threshold or 25 psi. You could also disconnect the harness at the switch and jumper the connector terminals with a paperclip. That will keep the circuit closed and the compressor running - though if it's low on gas you will, at best, get a bunch of ice on the Evaporator and lines and at worst, blow up the compressor if it doesn't get enough lube and/or pop the relief valve and spew gas all over the place if the high side is backed up - so if you do this, don't do it for more than a couple of minutes.
Last edited by SunCr; Sep 2, 2009 at 12:56 PM.
