Automotive Air Conditioning Information Forum (Archives)

Racerguy01 on Tue July 31, 2012 1:53 PM

Year: 1998
Make: Volkswagon
Model: Jetta tdi
Engine Size: 1.9 l
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 21
Pressure High: 135
Country of Origin: United States

I have been having problems some times the air works good other times not at all when I checked it when it was blowing 37 degrees f every time I have seen the fans are on and compressor running.

Hope I can get this fixed! Thanks

GM Tech on Tue July 31, 2012 3:25 PM

You checked it (when inop) and it was blowing 37 --to me that is working fine!

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Racerguy01 on Tue July 31, 2012 6:32 PM

I agree it was working at the time. Most of the time it blows mid 70s or warmer. I have noticed that when it isn't working and I hook up the gauges it typically starts working.

ice-n-tropics on Tue July 31, 2012 7:13 PM

Roller TD,
Just a guess:
Maybe the SD7V17 variable displacement compressor gets stuck in minimum stroke (due to factors like internal friction) at idle, but when the engine is reved up, the variable angle cam breaks free and increases the stroke. This sticking can be aggravated by just a little low charge, internal debris stuck in the variable stroke mechanism or improper oil type or quantity. The lube spec is SP10 (DECPAG).
Another possibility is a MFCV (internal control valve) with the inlet screen blocked by debris.
hotrodac


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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

mollygomez on Fri November 01, 2013 1:32 AM

I don't think so that there is any sort of problem out there. You don't need to take load for that.