Air Condition Shut Down

[raffi]

have a 95 pickup. Just changed the o-rings on the pump and installed new ac cycle switch and added freon. The AC is nice and cold then about 20 mins the pump shuts off and stays off. It seem like if i turn everything to the off position for about 10-20 mins it will start back up. Any advice

[matthuber1]

Did you evacuate the system before you added the 'freon'? it sounds like you have moisture and non-condensables in the system.

[Draenor]

What are the high and low PSI? The system could be overpressurized.

[Zembonez]

What are the high and low PSI? The system could be overpressurized.

Or possibly a minimal restriction in the expansion valve area resulting in higher than normal pressure buildup... over time. Pressure switch should cut it off. It would eventually bleed down and come back on. I chased a similar problem on my Blazer for several months. It would cool for about an hour of normal driving, then just shut off. By the time I got it home to my gauges, the darn thing would come back on and read pretty normal pressures. Turned out that the expansion valve was bad and over time it would build up excess pressure. (I think GM called it an orifice tube?) It never acted up again.

[matthuber1]

What are the high and low PSI? The system could be overpressurized.

Or possibly a minimal restriction in the expansion valve area resulting in higher than normal pressure buildup... over time. Pressure switch should cut it off. It would eventually bleed down and come back on. I chased a similar problem on my Blazer for several months. It would cool for about an hour of normal driving, then just shut off. By the time I got it home to my gauges, the darn thing would come back on and read pretty normal pressures. Turned out that the expansion valve was bad and over time it would build up excess pressure. (I think GM called it an orifice tube?) It never acted up again.

 

 

 

This also happens when noncondensables are in the system. Also if moisture is in the system it would freeze at the expantion valve or orfice causing a restriction.

[Draenor]

Jim and Matt said "oriface''.....

 

 

[minibike132]

huh huh yea oriface.

[matthuber1]

lol

[raffi]

You guys are right on when you say it over builds pressure. As soon as i got home i hooked up the cheap high psi gauge and the psi was normal. After about 20mins the PSI climbed and shut off. It started about 25psi then 30psi and then spiked. I'll have to look into the Orifice. Is this hard to change where would i find it? I did vacuum the system for about 1 hour before adding the freon. I have to check on the oil my buddy did it he usually knows what he's doing. I'll have to ask. You guys are great. thanks

[raffi]

I just check. My friend said there was no evidence of a major leak of oil only freon. So we only add the freon after changing the o-rings on the compressor. Looks like we are going to try to change the orifice and vac the system and refill with freon. Thanks for your help

[matthuber1]

I just check. My friend said there was no evidence of a major leak of oil only freon. So we only add the freon after changing the o-rings on the compressor. Looks like we are going to try to change the orifice and vac the system and refill with freon. Thanks for your help

 

 

Depending on your model year there is also a strainter/filter/dryer in the system. If your buddy knows a/c he should know about that too. Just something to check.

[minibike132]

If you have a normally operating system when you shut the key off the pressures should equalize fairly quickly. If you have a restriction as in the oriface the pressures will not equalize quickly. Just something to check before you go ripping into it.

[minibike132]

Doh I forgot about the first thing to be checking in an over pressure. Check air flow, Check that there is nothing blocking airflow in front of or behind the condenser and check fan clutch operation. If it takes 20 minutes to shut down this is very possible. For some reason I was thinking it shut off much quicker.