low side low, high side high, compressor cycling

Friendly format provided to inquire about automotive a/c systems.
Archived Forum

Moderators: bohica2xo, Tim, JohnHere

Post Reply
sfranchuk
Posts: 1
Read the full article
Joined: Tue Sep 20, 2016 10:55 am

low side low, high side high, compressor cycling

Post by sfranchuk »

Year: 2009
Make: Acura
Model: TL
Engine Size: 3.5L
Refrigerant Type: R-134
Ambient Temp: 90
Pressure Low: 25
Pressure High: 250
Country of Origin: United States

Hello everyone. I was hoping to get some help solving my AC issue.
Here is my current situation
AC is blowing cold air but not nearly as cold as it should be. My compressor is short cycling on/off roughly every 10 seconds. I connected the gauges and observed the following: Compressor kicks on and the low side pressure drops to 25psi at which point the compressor shuts off and the pressure climbs to 40psi before the compressor kicks on again and drops the pressure back to 25psi. The high side starts with about 200psi and grows to 250psi during this same cycle with the car at idle but has gone past 300psi with the engine revved up to 3000rpm.

Some background history on this issue
I replaced the AC compressor due to a leak at the shaft seal. Took it to the shop and they charged the system using their machine. A short while later, my accumulator(attached to condenser) blew out the plug and lost all the freon as I was starting my car on a hot 100+ Fahrenheit day. I replaced the condenser unit and took it back to the shop. They vacuumed the system added oil, and charged R134 to the spec'd amount. I was surprised by how much oil they added (looked like 3-5oz). I believe the whole system is spec'd for 5oz but not sure if I would have lost ALL the oil when the system blew. I got home and noticed the system is short cycling. I got a gauge set, and observed the low side cycling between 25 and 40 psi while the high side was more steady at 170-190 psi. I figured the system is undercharged and added a few oz of R134 at which point the high side rose to 225 but does not remain constant - it cycles between 200 and 300 as the compressor kicks on and off. The compressor currently does not cycle AS OFTEN but still keeps cycling every 15-20 seconds. I bled the low side a little bit and got quite a bit of oil on the rag which leads me to believe that there is too much oil in the system. But on the other hand, I think my system was short cycling even before the compressor was replaced - probably due to low freon due to the leak - but I didn't pay as much attention to it previously.

Any thoughts?
GM Tech
Preferred Member
Posts: 193
Joined: Fri Apr 22, 2016 7:22 am

Re: low side low, high side high, compressor cycling

Post by GM Tech »

Put the factory specified amount in it- then test....too many variables if you don't know how much refrigerant is in there...If you extract and weigh charge- you'll know if you have a leak-- then look for oil and dye evidence-- or have a sniffer ran over it..
jeepsj
Posts: 77
Joined: Mon May 16, 2016 1:41 pm

Re: low side low, high side high, compressor cycling

Post by jeepsj »

Mist your condenser with water when it is running and let us know what the high side does.
99 Jeep XJ
87 Jeep Grand Wagoneer - 6.5 turbodiesel
87 Chevy CC Dually
Post Reply