300M A/C pressures way too high (solution)

I finally got annoyed with the dealer and decided to just fix my '99 300M
A/C myself. Fortunately, I have the facilities (space/tools/knowhow) to do
it myself. A recap:

A/C slowly grew more and more inefficient until I was only getting about 10
degree drop from ambient.
I checked the pressures and found that the low side had an excessively high
pressure and the high side seemed normal.
I bring it to the dealer since I assume it's a bad compressor.
The dealer says "it's fine, we just put some more 134A in it." They send me
home.
It doesn't cure the problem.
The compressor short cycles and I see refigerant oil on the oil filler
nozzle (compressor is venting).

So I decide that these clowns just don't care or aren't able to diagnose the
problem. I decided to completely
evacuate the system and recharge it from scratch. I hook up my Robinair
recovery machine and note that it
inhales 37oz of 143A. Bingo! A full charge is supposed to be about 1.5
pounds or 24oz. I blow all the old
oil out of the system, evacuate it for 2 hours then refill with a couple
ounces of PAG + 24oz of 134A. And
it works beautifully. I just hope those idiots didn't damage my compressor
by overcharging it by nearly 50%.
I guess that's what I get for being lazy and not just doing this myself from
the beginning. So much for
trusting your local "5 star" dealer.

Cheers,

C

 

Festive. So you had a flooded evaporator and a short-cycling compressor
due to the HPCO activation. Yep, that'll drop efficiency right through the
floor!

I'm curious what technique you used to do so.

Probably not -- the HPCO kept system pressures from climbing too high. The
weakest link is the compressor shaft seal; if it didn't let go (and it
sounds as though it didn't) you should be fine.

DS

 

Sorry, I did not catch - what was an initial cause of the problem?
Ok, the dealer overcharged your system, but it was AFTER something happened.
Did you find what was wrong?

Regards,
Alex

 

I was reasonably thorough, but not completely anal about it. I disconnected
the hoses leading to the expansion valve, blew the lines out with compressed
air, then did the same thing with the evaporator and condenser. I then took
the lines off the compressor, removed it and hung it upside down for 15-20
minutes to get as much out of there as possible. I replaced the
accumulator/receiver/drier since I had no idea what those buffoons put in
there...better safe than sorry. Then I added a few ounces of PAG, put
everything back together, evacuated the system (it held the vacuum for an
hour or two so I knew it didn't have any major leaks) and recharged it with
24oz of 134a. Had I realized just how much of a pain in the ass it is to
adjust the A/C belt, I probably would have skipped the compressor step.

Cheers,

C

 

Not sure. The initial symptom was that the system was not cooling
adequately and when I checked it out there was abnormally high pressure on
the low side. I'm thinking that there must have been a blockage somewhere
because when I cleaned it out, evacuated it, and recharged the system things
worked as expected. This was the first problem I had with the A/C.
Historically, it has worked extremely well. Now I know not to let the
dealer touch it. That's what I get for being lazy and trusting.

Cheers,

C

 

I'm with you on it!

Regards,
Alex

 

Yeah. I have an extended warranty and thought the compressor was shot so I
figured I'd let someone else deal with the pain in the ass of changing it.
Oh well.

C

 

My Final Dealer Experience (tm) also involved A/C. Several years ago, my
wife's 93 Vision TSi finally blew out the evaporator core, as virtually
all early first-gen LH cars did. I let the dealer replace it, and over
the next year the A/C worked fine, but the compressor grew increasingly
loud. Well, it did have 120,000+ miles on it, so I figured it was just a
typical crappy Japanese-designed compressor (Nippondenso) getting noisy.
It finally seized, and so I replaced it myself. To make sure it hadn't
sprayed its guts throughout the system, I disassembled it, and guess
what I found? NO OIL. Just a thin film. One of the pistons had seized to
its bore and locked up virtually instantly- no aluminum shavings made it
further than the valve block, so none got into the system.

One rebuilt Nippondenso, one FULL load of PAG oil, pull a vacuum, put in
the recommended charge of R-134a, and its been fine for about the past
80k miles (the car just passed 200,000 miles a few weeks ago).

I *know* there are good mechanics working in dealerships out there. But
I think there is huge institutional pressure to cut corners, perform
unnecessary work, and NOT perform some critical checks (like verifying
the system oil level following a refrigerant leak!!!) in order to stay
"profitable" no matter how pissed the customers become.

 

I *know* there are good mechanics working in dealerships out there. But

At the small brand 'LM' dealership for which I briefly worked as a service
writer 12 years ago, the owner made no bones about his strategy: 90% of the
revenue for the business came from the service department. Car sales in a
smaller operation are often not enough to support the business; you have to
generate good service revenue. Hence the accelerated routine service
schedules, the blatant ripoffs ($65 to change 4 sparkplugs, for example, at
a time when labor was ~$40/hour) the foisting of the hard-to-diagnose or
reproduce problems back onto the customer ('Couldn't verify problem'), etc.

--Geoff

 

the flat rate pay system is the cause! it was a pay system designed 80 years
ago

 

Good old D-C dealers.... I've got a 2001 Caravan that just had it's FOURTH
shot of 134A. Two time, a year apart, I complained about poor cooling. They
say it's fine, until we go for a ride, and it's lukewarm. They evac, and
find it's real low. They recharge, with dye. Later in the Summer of '01,
it's not cooling well - when moving. They check it standing still - I'm not
there - and they pronounce it working properly. We go for a ride, and they
say "yeah, it's not cooling". They add 134A, and it works. Summer of '02,
repeat. They say they don't see any leaks. Summer of '03 - different dealer.
It's cooling fine, they say. I send them for a ride (they just did a
transmission repair on it also), and they decide it's not cooling. PS: they
had to tow it back 'cause they didn't fix the transmission, either. They
evac, and find .8# and they say a full load is 3#. They said I need to come
back within 10 days for them to look for the leak (they actually had it that
long trying to fix the transmission). It's cooling like crap again, and now
they say that the problem is the controller. They didn't see the humor when
I suggested that the source of the leak isn't likely to be the control
module in the center console, and that they check the charge again, even if
they don't see dye leaking. It seems I've been thru alot of refrigerant with
no leak repairs to be blaming the problem on electronics...

 

Flat rate isn't so bad when you're doing straight forward
repair work, it's when heavy diagnostics are needed that the
system falls short. That and all the special policy labor
ops which are nothing more than some junior VP dumping his
f*&k-up on the backs of the mechanics.

Hell, I remember the final brake recall GM had on the 1980
"X" bodies, install new shoes, cut the drums, replace the
parking brake cables from the pedal back, adjust everything
'just so.'

Paid 5.7 hours, took 1.5.
But back then, we had to walk 20 miles thru 4 foot snow
drifts, up hill both ways to the training center...

 

It was real strange - I new nothing about the auto industry at the time,
and I was in my early 20's. I called information, and somehow (don't
remember how I did it) I got thru to an actual brake engineer somewhere
within the bowels of GM. The guy actually told me the history of how
the problem got created, and told me that the real fix would be to put
on rear shoes from an auto tranny car - and he ended up by saying that
if I ever said he gave me the information, that he would deny it - this
was very early on with the problem before it was known by the public.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

Yup, we knew at the dealership level that using the part
number for the automatic equiped cars yielded improvements,
except that we couldn't do it due to liability reasons.

I believe that the 1980 GM X chassis still holds the record
for the vehicle with the most recalls ever issued.

 

And as cars get more complicated, MORE heavy diagnostic time is needed.
The system needs to adapt with the times, don't you think?
..

 

I'd make an intelligent comment, but I'm still trying to figure out how
you'd get a fart INTO a driving helmet....

 

Uh...Neil? You're wearing your diving helmet wrong.

DS

 

Careful what you compare it to, Neil - some people here might think
that's a good thing.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

That was me. And I was also thinking it is a way for the manufacturer
to
make the system self-documenting to the point where they don't have to go to
the bother of printing up and distributing manuals.

These days web servers can easily fit into an engine computer. Take a look
at this
one http://www.siteplayer.com/ the chip that runs it is smaller than an
ethernet
connector.

Ted

 

My 99 Intrepid (LH, same a/c system) has had short cycles ( and a loud
hiss! when the compressor engages since day 1.) Dealer said there was
nothing wrong with the loud hiss, nor the frequent (every 14 seconds or
so) engaging of the compressor.

I have always wondered if it was cycling on the high pressure cut-off
switch and asked the dealer about that. They simply said that there
wasn't a spec. for cycle time intervals. I can't find one either in
the svc manual.

Meanwhile, the a/c does get cold, but those constant hisses (loudness
depends on engine RPM) are annoying since they occur every 14 seconds.
More recently I have also noticed more of a rumbling sound (like you
would hear from a muffler that is starting to go south) that also varies
in loudness with engine RPM. Anybody have similar experiences?