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Old 08-19-2005, 10:40 PM
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Join Date: Jul 2004
Location: Palm Springs, CA
Posts: 166
My compressor was shut off today by high pressure cut-off

The ac pressure switch shut down my compressor today. I installed the ACM 2 bar low and 30 bar high switch last year. I left the car idling with the ac on low fan while I went into the mini-mart. It was 4 PM and 105 degrees. When I came out five minutes later I could smell a strange burnt smell about fifteen feet from the car. Engine coolant temp was 85 Celcius, no problem there. I immediately noticed that the vent temp was completely gone, blowing ambient temp air. On low fan speed the temp always stays very low, even at idle. After I began driving down the road and vent temps remained 100 plus, I knew I had a problem. I turned off the climate control. Then at a stop light I smelled the strange burning that I smelled before getting into my car. I thought I had fried my compressor clutch. I looked it over. That is where the smell was comming from, but it did not appear to be fried or frying (if you've ever seen a compressor clutch frying, you know what I mean). So, I decided to drive the car straight home with the ac off. I suspected that it might be the high pressure cut-off so after I drove a couple of miles at 60mph (evap pressures lowered) I fired up the ac and it was cold within ten seconds. Wow, that was scary. I had a broken ac last July and suffered for two weeks in 115 degree temps. One thing I'm wondering is what kind of damage might have been done to the compressor at the 30 bar cut off point?

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Old 08-20-2005, 10:17 AM
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Join Date: Sep 2001
Location: central Texas
Posts: 17,281
Well, unless your condensor AND radiator were both pristine and with no bent fins... and your aux fan was a superhero model.....I think everything just worked as could be hoped for and expected... that was an extreme condition for the system.
I can imagine your relief when it started up again....
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Old 08-20-2005, 06:00 PM
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Location: Palm Springs, CA
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After thinking about it for a while I think the strange (electrical burning) smell was comming from the clutch as it looks like it got really hot. It's a new compressor as of last year and looked in almost new condition before the incident. Now the metal of the clutch looks brown and burnt, like it got very hot. What is 30 bar equal to in temperature and pressures? I thought the pressure cut-off was around 400.
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Old 08-20-2005, 06:09 PM
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1 bar = 14.5037738 pound/square inch [absolute]

30 bar = 435.113214 pound/square inch [absolute]


1984 300SD Turbo Diesel 150,000 miles

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