A/C Problems

1429 Views 11 Replies 6 Participants Last post by kepalo, Apr 5, 2015

iaff284

Discussion Starter · Apr 2, 2015

We had a couple of warmer days and I noticed my A/C was working intermittently. It works at idle, but any rpm up to 2K and it will start cycling on and off every 5-7sec. At 2k it will stay running longer up to 2 min before it cycles as long as the fan is on high and the A/C is set to max. I put my gauge set on it and found the following. The temp was 70 deg. with low humidity and the truck hadn't been run for several hours. All readings were taken with the A/C set to max, the doors closed and the fan on high.

Static Low 87 High 92
Idle Low 35 High 140
On Low 20 High 160 *the compressor cycles on and off every 5 sec
Off Low 40 High 70 *this is the pressure the system returns to before cycling again

If I leave the A/C on max with the fan on high and stay above 2K the compressor will run for 2 min before getting below 20 and cycling off. If I turn the fan down and keep the rpm the same the low press. will drop below 20 quickly and the compressor will start cycling. Any lower rpm and as soon as the compressor kicks in the press drops within a couple of sec below 20. Any help is appreciated

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Gpracer

· #9 · Apr 2, 2015

iaff284 said:
Au7point3, I put my gauge set on it already and obtained the numbers in the origional post. The air gap was out of spec on the clutch last fall so I replaced it already. I was thinking that it was low on freon as well but the static reading seemed appropriate for the temp. I was afraid to overfill it. the static seems high for 70 deg?

Static pressure (compressor not running) means nothing.

As soon as you have enough Freon in the system where some of it is liquid form, the pressure will always be near the same for a given temp.

In other words, a 30 lb tank of Freon at XX degrees will be the same static pressure if it has 30 lbs or 1 lbs in it as long as there is still liquid in it. The liquid stops expanding at a certain pressure for a certain temp.

Sounds like low charge for sure.

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