So I got home from work today and my AC would only blow warm air at an idle (600-RPM). I noticed a slight odor of burnt rubber (compressor belt perhaps?) I promptly attached the R134 refill hose/gauge I'd kept for the past month and it pegged off the chart. (high pressure) That refill kit hose/gauge thing has always had a normal pressure reading when I've checked the refrigerant pressure at an idle...(until today). Now at idle the compressor is not cycling on/off and I don't recall the radiator cooling fans kicking on either? The AC still blows nice cold air though when I raise the RPM's above 1500. Am I missing something here? I set the outside ambient temp dial at 75 when I charged it last month. Oh, it's my 1999 Legacy L wagon.

Seems like your TXV isn't working.  To really diagnose it you'll need a full gauge set, and you should be charging by weight.  But I guess you could just replace it and see what happens.

you must have a fan (probably 2) going at idle with the a/c on. That can definitely be a problem. Sometimes people report decent cooling on the highway, warm temps when they are at a stop light. That's because the fan isn't working and clearly there's air moving thru the condenser at highway speeds even with a bad fan.

 

of course, there are plenty of other ways the system can fail. Often, the 2 o-rings at the compressor slowly leak out enough refrigerant to prevent the system from working properly. Or pressure sensors can go bad, etc.

 

read here; http://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/43428-diy-c-air-conditioning-leak-refrigerant-repair-5-less-15-minutes-less.html

Edited July 1, 201411 yr by 1 Lucky Texan

So I google searched and read that the TXV is a metering device/valve and will cut off the compressor if pressure gets to high? I'll keep an eye on things today and see what happens. I don't know why the pressure is reading (abnormal/high) when I only put one can in the system? 18oz if I remember right? It was the silver-gray can of R134 with blue print.

So I google searched and read that the TXV is a metering device/valve and will cut off the compressor if pressure gets to high? I'll keep an eye on things today and see what happens. I don't know why the pressure is reading (abnormal/high) when I only put one can in the system? 18oz if I remember right? It was the silver-gray can of R134 with blue print.

 

 

well, suppose the system was only 10 oz low? you are now overcharged.

So when you hooked up the gauge you also added more refrigerant?  Or was this the last time you charged the system a month ago?  I assume it was working correctly a month ago?

 

You really should be charging by weight.  But this requires you to evacuate the system and then add just the right amount back in.

 

The TXV is a metering device but it operates continuously.  It adjusts the flow of refrigerant to get the right temperature at the evaporator.  It can fail various ways but one failure mode is that the low side pressure will vary greatly with engine speed.

If you smell burning rubber the compressor belt may be slipping at idle. Does it feel loose? Does the ribbed side of the belt look shiny?

 

You could also have a slipping harmonic balancer (crankshaft pulley) which could cause the compressor to not turn fast enough with the engine at idle speed.

I found the problem this evening. I put a new belt on and it's working just fine. Thanks for the input people. Just can't overlook the obvious when it comes to the automotive world. I forgot to check the pressure of course. I hope I didn't overcharge the thing last month?  I'll check it tomorrow.

Edited July 2, 201411 yr by darsdoug