Aircon question

[karl1171]

Is the compressor supposed to run continually when the aircon is on?

My clutch engages and disengages periodically. If this is a fault is it the compressor or another component?

[Paul in NZ]

Is the compressor supposed to run continually when the aircon is on?

My clutch engages and disengages periodically. If this is a fault is it the compressor or another component?

it does not run continuously in my experience

[filmy540i/6]

The compressor (and therefore the A/C) would be "on" when the clutch is engaged. Between the temp selection and whatever expansion valve BMW uses, yeah, the comp could shut off temporarily if it isn't under control to stay on continuously.

Another couple of things that might/could disconnect the A/C clutch: hard acceleration - lots of cars do this, maybe all of them these days. Lets the engine use all of it's HP for moving the car instead of comfort luxuries; and 2, if your refrigerant is low, the low pressure will stop the system from functioning to save the compressor from eating itself.

Or the clutch itself may be worn out.

[shogun]

It is normal, you have a pressure switch.
The pressure switch senses internal pressures and can cycle the compressor off and back on based on minimum and maximum pressure limits.

[Ross]

Normal operation unless it cycles very frequently, that usually indicates a low freon charge.

[bsell]

It is normal, you have a pressure switch.
The pressure switch senses internal pressures and can cycle the compressor off and back on based on minimum and maximum pressure limits.

True enough, but aren't the pressure switches 'safety' switches that prevent serious problems (i.e. no freon or too much) from wiping out the compressor/and or condensor/evaporator?

There should be an anti-ice switch on the evaporator. It turns off the compressor once the system has caught up with the thermal load and the evaporator is getting cold enough to ice over.

It helps to remeber the wide range of temps and humidity levels these things operate through. Plus, the a/c's are sized for some pretty extremely hot areas so they have excess capacity for most folks/situations. Thus they don't run flat out all the time.

So if the OP has plenty of frigid air blowing out the vents and the compressor doesn't cycle too quickly, then everything is peachy!

Brian

[93AlpineII]

Normal operation unless it cycles very frequently, that usually indicates a low freon charge.

Maybe it would be helpful if some of us would describe "normal". In my case (not sure of any system rework; 91K miles, with a new cabin filter), on a humid 95-degree day, I believe my compressor runs for about 30 seconds and is off maybe 15 seconds. These are estimates of course and the cabin gets cold enough that I have to turn up the thermo to about 72 without freezing hams. Now, hopefully I didn't jinx it....

[Paul in NZ]

Maybe it would be helpful if some of us would describe "normal". In my case (not sure of any system rework; 91K miles, with a new cabin filter), on a humid 95-degree day, I believe my compressor runs for about 30 seconds and is off maybe 15 seconds. These are estimates of course and the cabin gets cold enough that I have to turn up the thermo to about 72 without freezing hams. Now, hopefully I didn't jinx it....

more mild where i live....90 535 250 000 kms blows cold but not as cold when i first got it 6 years ago,seems to cycle about 30sec on 30sec off

[shogun]

worth to bookmark this page autoactraining.com

Auto A/C FAQ's - Top 10 Lists
http://autoactraining.com/artman/publish/cat_index_22.shtml

[bsell]

worth to bookmark this page autoactraining.com

Auto A/C FAQ's - Top 10 Lists
http://autoactraining.com/artman/publish/cat_index_22.shtml

Nice link!

1,500 square feet rating for a car A/C! Who would have thought?

I almost laughed at the flashback to A/C 101 caused by this line, 'the a/c doesn't make the air cold, it removes heat...' I see they are still peddling that same 'scientific' idea, 23 years later!

Whatever the semantics, 'air with less heat' feels cold to me! Up with cold, down with heat!

Brian