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Here's a wild thought (m) (archive)

[ Follow Ups ] [ 5-series (E34) Message Board ] [ Msg. Board FAQ ]

Posted by dudel on August 29, 2001 at 20:31:15:

In Reply to: (Help) AC is Cutting of Engine Power posted by Katco on August 29, 2001 at 07:07:48:

I had this happen on my Jeep Grand Cherokee. See if this makes sense.

If your refrigerant level is low, the compressor has to work harder to cool. Most compressors have both a thermal cutout and a pressure cutoff (both are there to protect the compressor).

So, you go driving around (steady speed highway)and your cuts out due to low pressure / overheat. When it cuts back in you feel a loss of power (might be more noticable in a 525i) then the engine picks up the load and all seems normal. This problem of course would not exist if the A/C were off.

Try this: while driving, cut the a/c on then off. Do you get the same power loss (fraction of a second) feeling?

Let me know. This is an interesting one.


I noticed that when I switch on the air conditioning in my 1989 BMW 525 I,after a couple of minutes, it cuts off the engine power for a fraction of a second during normal driving; the check engine light blinks once, and it
gets back to normal.

This usually happens between two and four times during
a normal trip when the air conditioning is on. However, this problem does not exist when the air conditioning is off. The check engine code reveal that the relay switch for the fuel pump is faulty, and changing this relay twice has not resolved the problem. In addition, I have changed most of the relay switches and a lot of BMW shops have been unable to diagnose the problem.

Please can anyone assist me with identifying the probable cause of this intermittent engine power cut off when the air conditioning is in operation????????

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