Engine Size: 2.6
Refrigerant Type: 134A
Ambient Temp: 85
Pressure Low: 42
Pressure High: 290
Country of Origin: Mexico
Last year we replaced the compressor, dryer & expansion valve on our Jetta. The system was flushed and vacuumed to -15 before charging.
It worked great all season but this summer it does and doesn't work . Here are the details:
for both of the below results the a/c was on high speed set at the coldest setting
car cold, after sitting overnight - outside temp 85, compressor engaged, low pressure 42, high 290, center vent temp is 50
car cold, after sitting in sun for 4 hours - outside temp 95, compressor engaged, low pressure 70, high 140, center vent is 90 to 100
Where should I begin to look?
Took the car for a quick spin and when going 50+ MPH the vent temp starts dropping from 90 to 60. As soon as I stop or when going under 50 the temp rises again.
Appreciate any advice because I'm really stumped on this one.
Edited: Sat July 23, 2011 at 1:26 PM by dschein
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Where was the compressor sourced from?
It sounds like the control valve on your SD7V16 compressor is intermittently sticking open, causing the compressor to destroke. Good news is you likely don't need to replace the compressor, just the control valve. You should be able to inexpensively source one from the site sponsor.
Also, unless you're elevation is around 16,500 feet, -15 in hg of vacuum is not at all sufficient, and you likely have moisture in your system - which could be wreaking havoc.
Thanks for the response. It was sourced from techchoiceparts.com along with all the other new parts (except the freon).
I presume the theory is that the control valve gets hot and sticks open, correct? The VW service manual is on the table and later today I'll review the A/C section to ensure I understand what / where the control valve is.
One question, could the control valve work normally some times and stick other times? The reason I'm asking is because this AM I drove it about 3 miles to the store and it had the heat related behavior (warm air at idle). However when I left the store for home it worked perfect, I had cold air at an idle with a hot engine and outside temp of 95. After getting home I let the car idle for about 3 mins, it was still blowing cold air.
After doing some googling I found this link that shows replacement on a GM version of my compressor. Looking photos at the replacement part
it looks like the control valve in the SD7V16 is very similar to the GM model and will require disassembly of the compressor. That would explain why there is no mention of the control valve in the VW manual (replacement of the compressor is recommended).
Edited: Sun July 24, 2011 at 1:49 PM by dschein
I never said anything about not needing to discharge the system. Not only do you have to discharge the system, you have to remove and disassemble the compressor to change the control valve.
With that big drop at speed... Are the condensor fans working?
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
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