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many solutions (archive)
[ Follow Ups ] [ 3-series (E21) Message Board ] [ Msg. Board FAQ ]
Posted by david on June 20, 2000 at 17:02:57:

In Reply to: Need help w/ AC compressor clutch not engaging posted by DHoang on June 20, 2000 at 08:20:20:

: ON the way home from a rather normal drive, the AC on the E21 323i just decided to stop blowing cold. With the motor running, I can see that the AC comp. clutch remained dead stationary while the fan belt spun freely on the pulley. I got inside and switched back and forth on the AC switch but no AC, and no clutch engagement. I went to the fuse box to check for any blown fuses. I didn't see any blown. I then decided to see if the relay could be at fault. Since I don't know how to read German on my fusebox cover, I couldn't figure out where the relay is. I vaguely remember that the last time I investigated this, most of the relays existing were for fogs, hi, low lights, fuel pump,and one other that draws my mind blank at this moment.

: I then went to the compressor side and peeked at the sight glass. I saw small to medium size bubbles effervesce about there. Bubbles kept streaming through the glass.

: So I think I need to diagnose two areas - the AC relay & freon level. I don't really think it's the on/off switch at this point since it turns on the aux. fan. Can anyone help me with answers to the following:
: 1) Anyone know where the AC relay is located on E21 323i so that I can have it checked ?
: 2) Other than getting a new one to swap out, anyone know how to bypass the AC relay ?
: 3) Do the bubbles in the sight glass indicate freon loss ?
: 4) With enough freon loss, does this force the AC clutch from engagement?
: 5) Any other ideas for me to check ?

: Thanks in advance for assisting.


I think you checked good, but this is what i would also do : Take out the AC switch and see if the vaccum vaccum wire that goes into your AC system is not pierced or broken... it should be plugged into the evaporator, but has no freon communication inbetween.
If this line is broken your AC can still switch the fan on, but not the compressor as it would "think" the evaporator is too cold already... it would still allow to refresh the engine coolant.

The word for AC in German is Klimaanlage, which means in fact AC device.

As for the bubbles are concerned, this sounds really strange to be because you can only see bubbles while the AC is running... so this would mean that the cluch works...

So another possibility is that you froze your evaporator, but then this would come back to normal and you should get your AC again...

I can't remember well, but i think there is another relay for the AC that is located on the AC unit (near the evaporator... behind the AC switch somewhere) You may want to check this one also.

The pressure switch on E21 doesn't stop the AC in case of low freon level... it just regulates the pressure to avoid over pressure in the system... has no electrical connection to the clutch.

If you have a voltmeter, i would 1st check that some electricity arrives onto the compressor clutch... You don't need your motor to run... just turn the ignition without starting the motor and of course make sure you switch your AC on too.
If no voltage, check for electricity failure (relais... at least 1 or 2 and fuses).
If you have power coming to your AC clutch, then 2 possibilities : clutch failure... which i doubt because it is an electro-magnet that works pretty good... or other possibility : the clutch washer doesn't let the clutch move from ON to OFF.
Then if it stuck ON, your system will freeze : No AC... and if it stays OFF the compressor won't work.
To dismantle this you need to take out the freon and take off the compressor and dismaltel the AC clutch assembly... the washer may be rusted... i would check.
If ever you have a freon leak, just be aware that you may not see the clutch engage even if it does... which it seems to do with the bubbles in the sight window...
A freon leak would also result in no AC because the compressor woud just have not enough freon to cool down your air...
Good luck...
if you need any cluch diagram or compressor diagram or part # let me know.
David



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