Intermittent AC.

SCPOW

Hey guys,

I love driving my Wagon since it's a gas saver but with this hot weather and no AC I haven't been able to enjoy it much this summer.

Like the title states the AC is intermittent. My first thoughts were that maybe I was low on freon. I had the AC system drained, reoil, and refilled with new freon but the problem still persisted. The person who refilled the system said the AC clutch on the compressor seem "stuck" and when he taps the clutch with a phillips or something the clutch would kick on.

The AC turns on and blows cold AC when I first start up the car. I've noticed that the AC stops working when the car warms up. When the AC stops working (while the AC button is still pushed to the "ON" position) the car searches for idle; it fluctuates from 800rpm to about 1500rpm-2000rpm.

Any ideas? Suggestions are appreciated!

jb2wheels

I assume your AC is converted to R134A.

Does the AC work OK when it's cooler outside but get worse or quit when it gets hotter?

Mine did this because it was overcharged. My fault because I was charging and checking the low side and wanted to see 45 PSI at 90F per R134A charts.
Once I swallowed my pride and put gauges on the high side, too, I was seeing well over 260 psi on the high side. I assume this was shutting off the compressor. Also, the compressor would sap all the HP from my poor DPFI engine.

My car likes lower pressure. I bled off some R134A and dropped my high side pressure to around 240psi and about 95F. This also dropped the low side to about 40psi.

The numbers seem low based on the charts but the car cools better and the compressor is happier - doesn't sap all my precious HP. After more research, I think I still might be overcharged some. This link turned into a big pissing match but makes me want to drop pressures even more to 35/200 range. When it's 100F here my vent temps go up when I sit in traffic.

Check your pressures on both high and low sides and make sure it's not overcharged.

This might also affect your idle. Idle hunts when IACV can't control the idle. It might be doing this because the idle screw is turned way up to keep the engine idling with the AC on but when the compressor off, the idle would be way too high and freaks out the IACV.

Mine does the idle hunt when I turn the idle screw in too far to keep the idle up when the AC kicked on while it was overcharged. Since I dropped the pressures, I don't see as much idle fluctuation.

Or it could just be a bad compressor clutch.

arries289

Because your mechanic identified a 'sticking' clutch I would certainly be looking at that. Also, could be a bad low pressure switch. Regardless, if the heat load is there, the compressor should not be cycling off much. Keep in mind that too much oil and/or refrigerant can cause the system not to work. I think the idle issue is a separate adjustment issue being exaggerated by the cycling compressor.

MrJayDM

Just a thought....???
I cleaned the screen in my IACV and my wagon idles much better when my A/C is on!!

bam-bam

One other thing to check- these compressors have a thermal protector, intended to open and interrupt current to the compressor clutch if overheated. I don't know the temp. that the switch opens at offhand, but it's worth a look. Not a very common failure, but I did see one on a Sanden just recently.

Look for a doodad on top of the compressor, wired inline with the clutch. Easy to bypass for testing, but I wouldn't recommend leaving it bypassed. It's protecting a $300 part. If you have a Sanden, the overheat is a little black biscuit on top of the comp. held down by one screw. Easy-peasy. If you are cursed with the MatsuSHITa compressor, you'll have to lose the charge and probably remove the compressor to replace it. (Unless your eyes are on long stalks like a lobster and your 14" fingers have 5 knuckles each).

jb2wheels, 35/200 is better, and FWIW I've had good luck with 18-20 oz. charge of 134a.