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A/C issues intermittent cool air '99 Mystique 2.0L


New CEG'er
Mar 6, 2023
'99 Mystique GL with the 2.0L, years ago the a/c compressor clutch had utterly destroyed itself, and my solution at the time was to grab a shorter serpentine belt and just bypass it.

Fast forward to last year and this is my work DD, and I've gone from taking 10 minutes to get to work to 40, because my previous job decided it was time to go out of the country. So last year I managed (barely) to change out the clutch pulley without ripping the car apart- it was not easy I don't recommend it without the patience of Job, but anyway, I managed it, and then was low of refrigerant from sitting unused for so long, so I duly charged it using a manifold gauge set and generic ambient temp/R134 chart and also for good measure threw in a can or two of oil charge and a can of seal restore. Things have worked pretty well most of the time although last summer I did have a time or two it didn't seem to blow cold air for maybe five minutes at a time then fine the rest of the drive. This summer, that's gotten to be every commute, I'll start out with cold air, then it'll stop blowing cold. Usually it'll come back, either on its own, or if I just turn the A/C off a few minutes. Except the other day it went out and stayed out the rest of my drive home. When this is going on, the clutch isn't engaged.

I've looked at the pressures with a manifold gauge set, and don't see anything really amiss. It hasn't lost any refrigerant, the pressures are good, but the clutch turns off and stays off. Next morning, it'll come on. And run a little while, and then clutch will disengage and stay that way again. I run defrost a lot in the winter (above freezing so the assumption is the A/C kicked on), didn't seem to have any issues then, but now that it's the temperature of molten lava outside, it's decided to do this crap.

Anything simple I'm missing, before I assume the clutch coil is going bad? I had gotten a new coil with the clutch kit, and the coil in it isn't the prettiest thing in the world, but just getting the pulley replaced while on the vehicle was a real test of my grip on sanity, and the coil was one thing I decided just wasn't worth trying to replace with the compressor in the vehicle, on account of what had happened was the bearing in the pulley had gone bad and seized up.

I'm sure not in the mood to take it to an A/C shop, get the refrigerant recovered (will they even do it if I intend to work on it myself?), break the (then empty) system open, pull the compressor off along with everything else that will have to come out to get to it, then have to replace the drier so on and so forth- if it comes down to that coil I'm definitely going to try to replace the coil in situ before I throw in the DIY towel, but before I do could there be a pressure switch or something I'm missing that is a common failure? Which of course would then beg the question are such switches made so they can be replaced without venting refrigerant... I'm guessing no, yay.

Thanks in advance.
I've been poking around, and in the archives I've found the issues with clutch air gap- I don't see how it would have changed that much since I put the new clutch assembly on, but Occam's Razor being what it is, I'm going to drive it until it quits then get back home with it and try putting it up on ramps so I can get to the thing and give it a good whack to see if I knock it into running.
Years ago I had a Taurus where one of the AC line pressure sensors failed, which produced similar symptoms. IIRC I diagnosed this by removing the connector and jumping the contacts.

Replacing the switch would indeed open the system, but maybe you'll get lucky and it will just be a bad connection or loose connector. I do also think that some shops will recover to refrigerant as a standalone job.