Automotive Air Conditioning Information Forum

Hi All,

I have worked on A/C systems in the past, but I never saw the following issue before... The A/C suddenly stopped working so it wasn't gradual. The A/C blows warm and its the same temp as the outside air. The A/C clutch does engage and stays engaged. The low line DOES NOT get cold, but the high line DOES get hot. I hooked up the my gauges and without the engine running, the low pressure and high pressure are about equal at 100psi. When the engine/compressor is running, the low goes to about 35 and the high to about 175 and stays there constantly. The compressor never turns off. There are no leaks.

Could this be an expansion valve issue where its stuck closed since it just suddenly stopped? (I don't think this system has an orifice tube)

Please Help,
Thanks

Make sure your temp doors are working- go to full heat and full cold see if there is a differential. At 35 psi lo side- you should have cold return lines to compressor and cooling inside evap.

sgreiner1011 wrote:When the engine/compressor is running, the low goes to about 35 and the high to about 175 and stays there constantly. The compressor never turns off.

What rpm are those pressures measured? Should be like 1800 rpm.

sgreiner1011 wrote:There are no leaks.

Hmmm - "famous last words". 175 is low for high side pressure measured at 1800 rpm, you should next have the refrigerant pulled out and weighed, I suspect a leak. Leaks can even occur from bad service valve caps.

Make sure your temp doors are working- go to full heat and full cold see if there is a differential. At 35 psi lo side- you should have cold return lines to compressor and cooling inside evap.

Yes, I failed to mention this. The air is a lot hotter when I have it at full heat. When I have it on cool, the air temp is the same as the outside air.

What rpm are those pressures measured? Should be like 1800 rpm.

I think I tested at 1500 RPM for the pressures I mentioned. I am going to hook up the gauges again once I get the time (within a week or so). Now that I think about it, I may not have told you the right pressures. Those pressures may have been at idle. I'm suffering from CRS in my old age.

Hmmm - "famous last words". 175 is low for high side pressure measured at 1800 rpm, you should next have the refrigerant pulled out and weighed, I suspect a leak. Leaks can even occur from bad service valve caps.

Yeah I know about those words...LOL... Will a small leak cause the system to suddenly stop working?

I will be working on this car again within a week or so, I will post back. Maybe it will be sooner because its my daughter's car and we live in Phoenix where the temp is above 100 almost consistently...LOL

sgreiner1011 wrote:I will be working on this car again within a week or so, I will post back. Maybe it will be sooner because its my daughter's car and we live in Phoenix where the temp is above 100 almost consistently...LOL

Yep, I'm longtime Phoenix resident, now split time with cooler Prescott area....pretty unbearable down there ! "Love" those times when temperature is still 100F at midnight, or the "low" is 94F at 5:30am.....

Cusser wrote:

sgreiner1011 wrote:I will be working on this car again within a week or so, I will post back. Maybe it will be sooner because its my daughter's car and we live in Phoenix where the temp is above 100 almost consistently...LOL

Yep, I'm longtime Phoenix resident, now split time with cooler Prescott area....pretty unbearable down there ! "Love" those times when temperature is still 100F at midnight, or the "low" is 94F at 5:30am.....

When and if I ever get past this kidney issue. I really want to move to Prescott.

One potential root cause is that the single discharge valve of the scroll compressor is not fully closing which allows warm high discharge gas in the rear discharge chamber to re enter the scroll area. This is referred to as wire drawing and could be foreign material under the valve seat, cracked discharge flapper leaf spring valve material or a loose valve mounting bolt. The result is very little refrigerant mass flow and occasional clutch cycling due to thermal protection switch cycling at higher rpm.
A less likely cause is the fixed rear scroll o ring bypasses discharge gas into the scroll entry low pressure chmber.
hotrodac

Dug more into it, and at 1800 RPM, the low side goes really low to 5psi and stays there forever. The high side goes from 150 to about 155 or so and stays there. The compressor still runs constantly. At idle and static, the pressures are still the same as I mentioned before.

I'm thinking expansion valve... Thoughts?

Expansion Valve? Anybody want to give their thoughts? Vacuum on low end? Virtually no change on high side?

Is it an LX or JX model?

Recovering & inspecting the Expansion valve is the place to start with the low side dropping like that.