2nd Gen Non-Engine/Transmission Which a/c line is high and low pressure

[CEdwards]

After my compressor runs for about a minute the belts will start to squeal(new belt). I suspected something was plugged and my pressure was too high but now i'm not sure that is the case. My can of freon with guage hooks up to the small connector, is that the high or low pressure side? I thought it was the low side but now it would make more sense if it was the high side. I was going to add freon so I turned the compressor on for one minute till it started squealing then I turned it off and hooked the gauge to the small fitting and the pressure shot to 140 and blew the hose off. I read on here that the high side may run around 175 psi. Sound right?

 

[BILLVO]

You have it right the smaller of the 2 is the low pressure. If the pressure was that high on the low side then something is wrong. It has been a while since being into a compressor but I believe there is a screen in the low side port of the compressor. If this is plugged with debris it would build pressure on low side. How did you put the freon in the low side? with the can upside down for liquid or rightside up for gas? Low side charge while running needs to be gas or you probably slugged it with liquid. Just let it set for a while to equalize and recheck it.

 

[monkeyman]

The high side is near the passenger battery, never hook freon to that! Also AC will not take freon unless compressor is engaged, you might have to do it manually by by passing low and hi pressure sensors. Over filling with Freon is worse than under fill.

Rick

 

[JPenka]

Your low side should read somewhere between 20-30 psi, high side can be in the 200's, higher if the ambient temp is really hot. The pressure switches in the system should kick the compressor off if your low side is really that high! U need to have the system evacuated to see how much freon is in the system, recharged with the right amount. From there a shop should be able to read high and low sides and determine if there is blockage in the system. Typically the vanes in the compressor start to chip or break, and the orifice tube gets plugged with debris. This usually caused low low-pressure and high high-pressure readings though. Hope this helps.

 

[Pavemen]

the pressures will equalize when the system is not running, that is why you can see 120-150 psi on each side the system off. 40-50psi is the low side reading for a full system when the compressor is cycling.

the high pressure port is near the battery and the low pressure port behind the turbo, at least on my 99.

you fill the system from the low side, so the compressor can help suck the refrigerant into the system.

 

[JWestley]

if the line is hot its going to be a high side, cold is the low side. I would recommend taking your truck to a shop with a decent set of manifold gauges so they can tell you what is really going on with your system.





also just a little fyi for everyone, r-134a is NOT freon, its refrigerant

 

[CEdwards]

Thanks for the replys. I took it to a shop today and he said there is nothing wrong with it. The pressure was 50 on the low side and I can't remember the high side but everything was normal and he couildn't get the belts to squeal. I wasn't going to add freon it was just the only gauge I had available to check it. I turned the compressor off because it was sqealing the belt and then I put the gauge on without realizing it wouldn't give me an accurate reading since the pressure would equalize. I appreciate the advice since I know very little about a/c. I really can't totally fix it myself without the proper tools and equipment but I would still like to try and solve the problem before taking it to a mechanic, if nothing else to maybe do some of the labor myself. It will blow cold air because its cool outside but last summer it was only half as good as the year before and now sometimes the belts will sqeaul until I turn the a/c off. The only question I have now is can the system be low on freon/oil and the pressures check out normal? It seems as though the compressor has to run a while and get hot and then the belts will squeal (it was cold today maybe why it worked). Is the low side up high by the battery(small fitting) or low under turbo behind compressor(big fitting)? I was a little confused by the posts. By the way I did clean the radiators at the car wash.

 

[BILLVO]

Low side is always the smaller fitting. Next time belt squeels take a look while its happening to see if compressor is turning. You may have a dying compressor.

 

[JWestley]

Thanks for the replys. I took it to a shop today and he said there is nothing wrong with it. The pressure was 50 on the low side and I can't remember the high side but everything was normal and he couildn't get the belts to squeal. I wasn't going to add freon it was just the only gauge I had available to check it. I turned the compressor off because it was sqealing the belt and then I put the gauge on without realizing it wouldn't give me an accurate reading since the pressure would equalize. I appreciate the advice since I know very little about a/c. I really can't totally fix it myself without the proper tools and equipment but I would still like to try and solve the problem before taking it to a mechanic, if nothing else to maybe do some of the labor myself. It will blow cold air because its cool outside but last summer it was only half as good as the year before and now sometimes the belts will sqeaul until I turn the a/c off. The only question I have now is can the system be low on freon/oil and the pressures check out normal? It seems as though the compressor has to run a while and get hot and then the belts will squeal (it was cold today maybe why it worked). Is the low side up high by the battery(small fitting) or low under turbo behind compressor(big fitting)? I was a little confused by the posts. By the way I did clean the radiators at the car wash.

50psi is right around where you want your low side pressure, and there is no way that you will have an undercharge and normal pressures. Now it is possible to have a high low side pressure, and a low high side pressure, but thats a different story.