RE: air conditioner clutch intermittent

From: Bernd D. Ratsch (fasstdak@hotmail.com)
Date: Tue Jun 14 2005 - 09:56:33 EDT


Sounds like you have a leak somewhere. Look around at all the lines (and at
the compressor and condensor) for any traces of an oil film (at all the
sealing areas). If you don't see any, the common problem is the evaporator
- time to yank the dash and replace it.

Pressure on the low-side will be high (100-120) when the compressor isn't on
(normal)...when it turns on, you should be getting down to the lower side of
the pressure gauge (anywhere from 0-20 depending on humidity/temperature)
and the high-side should be around 200-300 (depending on system/vehicle). I
don't trust those "Red/Yellow/Green" gauges as they don't show you exact
pressures and you can't check the high and low sides at the same time -
makes for a much easier diagnosis when you can see both sides.

The compressors rarely fail (have had to replace them but only on higher
mileage vehicles - 80-90K+ miles) and only on occasion when the compressor
actually failed (but it is a possibility)...my bet is still the evaporator
though.

Do NOT keep putting those "fix all" refrigerants into the system as 2001+ DC
vehicle already come with dye in the system - no need to add any. Adding
the "R134a with Sealer/Dye/Conditioner/Oil" will hurt the system more than
you think. The drier/accumulator will plug up prematurely, the evaporator
lines and condensor lines will plug up, and the internals on the compressor
can plug up as well. Having too much oil in the system will also degrade
A/C performance.

- Bernd

-----Original Message-----
From: owner-dakota-truck@bent.twistedbits.net
[mailto:owner-dakota-truck@bent.twistedbits.net] On Behalf Of Peter Grace
Sent: Monday, June 13, 2005 2:56 PM
To: dakota-truck-moderator@bent.twistedbits.net
Subject: Re: DML: air conditioner clutch intermittent

I'm having a similar problem on my 1997 3.9L -- All I know is that the AC
gets nice and cool for a while, then after a few minutes of driving it
starts spitting out hot air. I looked at it in the driveway and it seemed
that even if the A/C was turned on, the clutch was not engaged.
Could this mean I need to replace the compressor? If so, how much moolah?

I topped it off with leak sealer/oil and a can of R134a, it seemed as though
it has a slow leak somewhere that I've been trying to fix for the last few
summers. More or less it's been me just buying new cans of R134a straight
to top off with.

The current pressure with the compressor disengaged is in the red zone of
the gauge (I think the reading is somewhere like 110psi) but once the ac
kicks on, the pressure is mid-yellow on the gauge.

Thanks,
Pete



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