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A/C works at idle, warms up driving
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ParkerFly
Novice
Aug 24, 2016, 1:41 PM
Post #1 of 6
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A/C works at idle, warms up driving
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I have an older semi truck that I'm having A/C issues with. The truck is running 134a and every component of the system has been replaced except the condenser (expansion valve, compressor is new Sanden, evaporator, etc). The A/C works good at idle, but after driving for a while it will still work but warm up by a good 10 degrees. If you turn it off for a little while it will start working again but soon do the same thing. This is opposite of every air conditioning system I've been around. Pressures are running around 30 on the low side and 225 on high side at roughly 90 degrees. I've pulled it back down and recharged to make sure nothing is wrong there but no difference. Also changed dryer and expansion valve a couple of times trying to figure it out. Can someone tell me what's wrong and what to try? Thanks,
Justin
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Hammer Time
Ultimate Carjunky
/ Moderator
Aug 24, 2016, 1:50 PM
Post #2 of 6
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Re: A/C works at idle, warms up driving
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Older truck?
How about year, make, model and engine size?
How much refrigerant is in the system, exactly?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ParkerFly
Novice
Aug 24, 2016, 2:08 PM
Post #3 of 6
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Re: A/C works at idle, warms up driving
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1978 Kenworth W900A, 855 big cam Cummins engine.
I didn't weigh the refrigerant going into the system because there are no specs anyone can give me on what it held from the factory, plus a sleeper A/C unit has been added on at some point which ties into the main a/c system.
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Hammer Time
Ultimate Carjunky
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Aug 24, 2016, 2:12 PM
Post #4 of 6
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Re: A/C works at idle, warms up driving
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OK, now I see why you left it out.
This thing could be freezing up but you really need to monitor pressures right through the issue to find out.
I assume this is an expansion valve system which means it should have a thermostat n the evap to shut it sown when it gets too cold.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ParkerFly
Novice
Aug 24, 2016, 2:45 PM
Post #5 of 6
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Re: A/C works at idle, warms up driving
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Correct that its an expansion valve system. Is there any easy way to monitor pressures while I'm going down the road and its doing this? Any possibility its overcharged?
On edit - forgot to mention I flushed the system also but it wasn't dirty.
(This post was edited by ParkerFly on Aug 24, 2016, 2:51 PM)
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Hammer Time
Ultimate Carjunky
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Aug 24, 2016, 2:59 PM
Post #6 of 6
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Re: A/C works at idle, warms up driving
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No, I would rule out overcharge.
You can attach gauges and tape them to the windshield but that's not a long range idea. The best bet is to simply hook them up when the problem is present.
We're basically trying to find out if the pressures are getting higher or lower when this happens. You also want to confirm that the clutch is still engaged.
I still think freeze up is the most likely cause.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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