RE: AC Power Loss

[Bill Samaras DTN 223-7322 03-Sep-1993 1306 <samaras@wrksys.enet.dec.com>]

I also have an 86 5000CS TQ. And, unfortunately, I've become *very* familiar
with the A/C system. These A/C systems work well when they are in good shape,
but there are lots of things that can go wrong.  There shouldn't be a big power
loss when the A/C is on. As a matter of fact, the system is designed to not
"feel" the compressor switch in. In my experience (on my 3rd compressor)
if the engine is loaded down with the compressor on, you either have a clogged
restrictor, or there's too much freon in the system (or both). This was one of
the 1st systems to use a sightglass-less configuration, and a separate control
system to prevent evaporator icing. Neat stuff, but *lots* of folks didn't
understand it in 1986. A common symptom was poor cooling which people
interpreted as low freon.  Ususally, the evaporator thermostat was bad instead,
but lots of folks added more freon anyhow. This causes the compressor to create
higher than normal pressure making the engine work harder. I had this problem
for a while before I "got it". The easiest way to know if you have this problem
is to check mileage. The A/C shouldn't kill mileage more than 20% or so.

There is a compressor cutoff switch on automatic transmission cars. I guess
they felt you need all the low RPM torque there is.  On 5 speed versions, all
of the wiring is there for the switch (it connects to the gas pedal when
floored), but the switch isn't there. At least in 86-87, this is how it worked.

It's strange to hear that there were GM compressors used on 5000's in 86.  Mine
has a Nippondenso compressor, and all the 5000's in junk yards have them. I
also know that the 80 and 90 models use the same compressor.  It's a good
design if you keep the system in spec.

Be cool,
...bill

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>Subj:	AC Power Loss
>
>My 86 5000CS Turbo (5 speed) has the same horrible loss of power when the AC
>compressor is on. My system has the larger GM compressor that was typically
>used on the GM V8 engines. Although the AC puts out a lot of cool air I
>find the power loss very annoying as well. I've noticed the factory manual
>wiring diagrams show a 1st gear AC cutout switch on some of the 5000 cars.
>Mine does not have this switch installed. I also use the ECON switch to shut
>off the AC when I want to accelerate quickly.