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99 Caravan mystery

craigecooper on Sat July 12, 2014 8:29 PM User is offline

Year: 1999
Make: Dodge
Model: Caravan
Engine Size: 3.3
Refrigerant Type: 134a
Ambient Temp: 90
Pressure Low: 35
Pressure High: 245
Country of Origin: United States

Great advice in the past on this forum for GM repairs so not a total noob but baffled by this one. I also have a '99 Caravan with dual AC. Lightly used, a little over 100k, mostly a road trip van and not every day driving. 100% original for all the AC hardware. Today the AC compressor totally stopped... no cycling. Engine off / restart ... no change so I drove it home. The posted readings 35/245 are with front and rear on high in recirc mode. Sorry, I can't locate my temp probe but the compressor is running non stop and the air is chilled pretty good. Never had a compressor just stop for no apparent reason. I left it running in the drive way for nearly 30 minutes with no issue. Does this make sense to anyone ?

thanks for all the help over the years,
Craig

craigecooper on Sat July 12, 2014 9:42 PM User is offline

Found the temp probe. Drove around for about 10 minutes. 90 ambient / 70 inside / 50 vent temps. That was on high recirc.

webbch on Sun July 13, 2014 10:33 AM User is offlineView users profile

sounds like you have an intermittent compressor engagement issue. Given the symptoms you describe, I'd be looking for excessive clutch gap because:
a) Compressor clutch appears to engage when cold
b) After extended period of driving time (hot), the compressor clutch drops out
c) brief engine off/restart doesn't fix - needs to cool down
d) Once cooled down, clutch engages again.

Not a guarantee, but certainly looks like a marginal compressor clutch gap to me. If you can re-create this scenario, try tapping the compressor clutch after it's dropped out with the engine running (if you can do so safely). If it re-engages immediately, you've found your problem.

wptski on Sun July 13, 2014 12:24 PM User is offline

Quote
Originally posted by: webbch
sounds like you have an intermittent compressor engagement issue. Given the symptoms you describe, I'd be looking for excessive clutch gap because:

a) Compressor clutch appears to engage when cold

b) After extended period of driving time (hot), the compressor clutch drops out

c) brief engine off/restart doesn't fix - needs to cool down

d) Once cooled down, clutch engages again.

Not a guarantee, but certainly looks like a marginal compressor clutch gap to me. If you can re-create this scenario, try tapping the compressor clutch after it's dropped out with the engine running (if you can do so safely). If it re-engages immediately, you've found your problem.
When would the clutch gap become smaller instead of larger? Most compressors aren't that easy to rotate, are a heavy engine load so it would have to fall apart and jam up.

With the engine the clutch should be released and one should be able move it toward the coil or just check for a gap.



Edited: Sun July 13, 2014 at 12:24 PM by wptski

craigecooper on Sun July 13, 2014 12:37 PM User is offline

Makes perfect sense and easy enough to test. If it proves out, a new clutch is required, correct ?

webbch on Sun July 13, 2014 1:24 PM User is offlineView users profile

Quote
Originally posted by: wptski
Quote

Originally posted by: webbch

sounds like you have an intermittent compressor engagement issue. Given the symptoms you describe, I'd be looking for excessive clutch gap because:



a) Compressor clutch appears to engage when cold



b) After extended period of driving time (hot), the compressor clutch drops out



c) brief engine off/restart doesn't fix - needs to cool down



d) Once cooled down, clutch engages again.



Not a guarantee, but certainly looks like a marginal compressor clutch gap to me. If you can re-create this scenario, try tapping the compressor clutch after it's dropped out with the engine running (if you can do so safely). If it re-engages immediately, you've found your problem.

When would the clutch gap become smaller instead of larger? Most compressors aren't that easy to rotate, are a heavy engine load so it would have to fall apart and jam up.



With the engine the clutch should be released and one should be able move it toward the coil or just check for a gap.

I guess I'm not understanding your question. It's pretty common that excessive clutch gap results in a failure of the compressor to engage....particularly when hot. Something I suspect you well know. Unless I misread the OP, he said his compressor stopped engaging, and the description seemed to imply that it occurred when hot. If it was a failure of the compressor to DISENGAGE, I could see how the clutch falling apart and jamming up may contribute to that situation, but that wasn't my assessment of the OP.

wptski on Sun July 13, 2014 1:51 PM User is offline

Quote
Originally posted by: webbch
Quote

I guess I'm not understanding your question. It's pretty common that excessive clutch gap results in a failure of the compressor to engage....particularly when hot. Something I suspect you well know. Unless I misread the OP, he said his compressor stopped engaging, and the description seemed to imply that it occurred when hot. If it was a failure of the compressor to DISENGAGE, I could see how the clutch falling apart and jamming up may contribute to that situation, but that wasn't my assessment of the OP.

I apologize as I didn't reread the OP and mistook the problem as being that it wouldn't disengage.

I've read the specs for clutch gaps and don't understand why they are so large, like .030"? All you need is clearance so if it's on the large size, it'll only get to the point where it won't pull in sooner.

craigecooper on Sun July 13, 2014 11:56 PM User is offline

it worked fine today but true test will be a longer commute during the week. I'll repost if it fails to engage again.

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