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A/C Blowing warm Air (all of a sudden)

2167 Views 15 Replies 4 Participants Last post by  manbat
Hi Gang,

Went out to run some errands today in my 94 Legend Coupe and when I left the store to come home, the A/C blew warm air instead of the ice-cold air it's been blowing for the last seven years.

I had to recharge the system a few years ago with fresh freon because (idiot that I am) I disconnected the A/C line to access one of the spark plugs near the rear of the engine where the A/C goes right over it in the way.

If I had never disconnected the A/C line, the freon would have never escaped and the car would still be running off of the original freon it came with.

To my knowledge, none of the A/C lines have a leak or have ever leaked, and I know enough to know that when they do leak - the A/C goes from ice cold to warm "gradually" not abruptly. (which is what happened today)

The problem is not the blower motor because air does blow - it just comes out warm. I also recently put all new belts on and all of them are fine.

I can hear the compressor engaging when I turn on the A/C, and every system I looked at seems to be in order, so I'm stumped at what happened today.

I looked at some of the troubleshooting sheets but none of that helped.

Has anybody else had this same problem where the A/C went from ice cold to warm immediately & abruptly, and if so - what did you do to fix it?

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Turns out the ac compressor clutch wasn't engaging.

For whatever reason the engine makes a change in idle speed each time the ac switch is depressed and I was mistaking "that" sound for the clutch engaging.

Today I physically watched the clutch while someone else was in the car cutting the ac on & off, and sure enough it wasn't engaging which leads me to believe that one of the fuses, solenoids or switches that are in direct line with the ac circuitry is shot.

I usually love these conversations with myself but if anybody else has experienced this and would care to offer some advice I'd really appreciate it.

I appreciate the fact that this subject has been brought up many times (and I did use the search button) but none of the threads I've seen on this subject have helped me.

Thanks in advance....
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The first thing you might try is adding some refrigerant. If the system is low, the clutch won't engage. Turn the AC on high and as you add refrigerant, the clutch should engage - assuming that's the issue. For $20-30, it's worth a shot.
Hopefully, your system uses R134.
Thanks but as I stated in my original post, it's full.

As a matter of fact I did buy one of those oversized refrigerant cans of the R134a with sealant & compressor oil just in case I was wrong, and my system won't take it because it's so full. (my system takes the R134a)

I suspected as much because I really baby the car and I didn't think the problem was a Freon leak.

Plus also like I stated in my original post, it just stopped blowing cold air "all of a sudden", not gradually over time.

I've owned many hoopty's back in the day where the ac would go from ice cold to warm over the course of a month or so because the Freon would slowly leak.

That wasn't the case with my car. She went from ice cold to nothing in the span of no time at all which now makes sense to me given the fact that I've discovered the compressor clutch is not engaging.

Unless one of the ac lines completely ruptures for whatever reason you won't lose all of your Freon in a matter of 1 minute.

I'm positive its got something to do with one of the ac switches that controls cutting on the compressor clutch, I just need to figure out which one.

Thanks for the reply.....
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Actually, you didn't say it's full, only that it can't be a leak because it happened all of a sudden. (If there was a pipe rubbing someplace, it would have leaked the refrigerant quickly.) If you've attempted to add refrigerant and it wouldn't take it, the shrader valve may be damaged. It's also possible that the clutch has failed.
The shrader valve isn't damaged, it's perfect, the system is completely filled with Freon, and there are no leaks anywhere. All of that is solid information.

I'm not sure how the clutch could fail but I guess it's possible, it looks like its all there and in-tact with nothing missing or broken off so I'm still deferring to one of the switches failing.

If the clutch or the compressor itself has failed then that'll be a major pain in the ass to change, so I'm hoping I won't have to.

The car has roughly 234.00 miles and I've already replaced the blower motor, and the ignition switch twice - which is another weak link of this car.

I read somewhere where the ac switch in these cars could also be a weak link, so I'm hoping that once I replace it, the clutch engages and she blows cold air again.
iirc, the switch that goes bad is located under the floor, by the ECU and that banging on the floor can actually get the AC to work.
IF the clutch is bad, it can be replaced without removing the compressor/emptying the system.
I ordered:

Part# 36129 $7.99 Relay (A/C Compressor)

Part# MT1440 $10.99 Relay (A/C Compressor Control)

Part# SW3017 $29.99 (A/C Switch)

All from AutoZone yesterday, when everything comes in and I replace them all, I'll report back.

Nice to know That I don't have to take the entire compressor off if all I have to replace is the clutch.

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I know it sounds nuts, but try opening and closing the glove box hard. If it's the switch by the ECU, the AC will,likely kick in.
Caution! Do not install Auto Zone relays may cause an electrical short on the box and/or the harness. Buy it at the dealer.
The link is for the Fan Control Unit (underdog the passenger floor, attached to the ECU.

Fan control unit: P/N 37735-PY3-901
Glad it worked out for you. The clutch on my '92 went out, which is how I knew that it could be replaced without removing the compressor. As for the squealing, it may have to do with the shims for the clutch. I don't recall what the gap is supposed to be, but if it's not correct, it will squeal.
Buy a new Denso ac compressor

I bought a 4 Seasons ac compressor, there was leak, could never find leak, sent
4 Seasons ac compressor back, replaced with a new Denso ac compressor.
All is well !
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