Last week I picked up a really clean '91 Pickup that hasn't been driven a whole lot the last year+. The A/C wasn't blowing cold. Initial checkout of line pressures after charging the system led me to replace the expansion valve and receiver drier. The system worked great and the pressures looked fine... until the compressor stopped. After the past few trips I've realized that the compressor will engage when I start the engine from completely cold, but go off after the engine warms up (about 5-10 minutes), and it will not come back on until the engine is completely cold again. Today on the drive home from work I didn't try and turn it on at all until I got home, but it wouldn't come on (assuming because the engine was warm again).

All I have is a '96 FSM I found online. Anyone know where I can get one for a '91? The push-button A/C switch in the cab doesn't want to engage every time I try and push it. I need to replace that, but I don't think that should be my problem if it stays engaged? Before the clutch disengaged the first time, the high side only got up to about 225psi before it disengaged, so I don't think it is the dual-pressure switch (although I haven't actually tested it yet - other than a wire jiggle - it doesn't seem to be a loose connection causing the problem). Other ideas only include possibly a bad relay or one getting hot (although without the FSM/Alldata I don't know where it would be - there are about 6 unlabeled in the engine bay); it was suggested that I check and see if the compressor is getting power when it is disengaged to see if maybe the clutch magnet is weakening or something (yet I haven't tested that yet); or perhaps a bad thermal protector (not sure if that is something I can test/replace if that year model even has it)...

Any help?

Thanks!

You'd think that since I live in Arizona, that I'd be an AC expert. Your issue does sound electrical, and with 16 year old wiring in your truck, it could be any number of things.

Search Ebay for FSM's The oldes ones I have are for a '95 Pathfinder, so I'm not sure how much that would help.

My '93 D21 consumes an ac control relay about once a season. The system is in pretty good shape otherwise ... this relay is just a bit weak. On my model it is held by one screw against the inside of the engine box (fender side) near the RH hood hinge.

This relay plus the mounting bar will cost you megabucks at the dealer ... but AutoZone will sell you an equivalent (you'll have to reuse the mounting detail) for about $13. Sorensen #41-5021.

Thanks... I'll check that out...

For some reason the other day it started working fine. I do still need the a/c switch for the interior, but I'll test the relay as well, for I think I've got some extra Nissan ones I may be able to use if it isn't tip top...

The relay won't die outright ... it'll just get flacky and run you crazy. I suggest a new, not used, one.

I also have a Nissan D21 hardbody pickup and am having almost exactly the same problem as BlazedGlory. Only I just spent about $680 having a new AC compressor installed with a new expansion valve and receiver dryer as well. It gets very cold for a while and then it just starts getting warmer and warmer until I have to open my window. After a while the compressor kicks back on (I can feel the truck kind of hesitate or kind of lag) and then it starts getting cold again. Then I roll up the window. It can stay cold for 5 minutes or 45 minutes. It's very annoying. Especially since I just sank all this money into having air conditioning. The first thing I did in an effort to troubleshoot the problem was replace both AC relay switches (just for Blazed Glory's information they are on the left side engine wall and are identical). That did nothing. My mechanic suggested I replace the dual pressure switch next. Unfortunately they are no longer available. First I tried Advance Auto and then Auto Zone and then O'Riley's and then NAPA but to no avail. Then I tried my local Nissan dealer. They are no longer available even with Nissan. Then I drove about an hour and a half to High Point NC to a Nissan junkyard. They had numerous Nissan D21 hardbody's but only one vehicle had the same dual pressure switch. I had to remove the part myself and paid $10 for it. What a steal! That is if it works. To tell you the truth the one in my truck looks like it's in WAY better shape.

Unfortunately I think all my efforts to get this dual pressure switch are in vain. I also know it is possible to check the continuity on the part so I am going to wait until the compressor shuts off again and bring the truck in to my mechanic to have him test it with an ohm meter (mine quit working about two weeks ago. Perfect timing!).

So does anyone have any suggestions? I notice that BlazedGlory is having a similar problem but his always comes on when he starts his truck. Mine does not. Sometimes it does and sometimes it doesn't. With mine it's kind of playing Russian Roulette. You just never know when it's going to work and when it's not. He says he has not yet tested his dual pressure switch. All I can say is pray that that is not your problem and if it is I hope you have better luck finding one and if you DO happen to find a new one somewhere PLEASE let me know where that may be! PLEASE! Again though I just have a feeling that is not the problem and I have no idea what that is at this point.

If anyone has any suggestions please let me know. At this point I'm willing to try almost anything .

Steve

Almost forgot...mine is a 1990 Nissan D21. Almost the exact same vehicle as BlazedGlory(coincidence? I doubt it).

Was this ever resolved?

Two people here with the same problem but none posted a resolution.......

I'm having the exact same issue with mine and it pains me to read all these problems and yet nobody posts their solutions.

Come on people, this is why forums die.