Burning smell... and lack of air conditioning... again. :(

[Ferret]

Okay, so this happened on my last E34 - the A/C compressor seized and the clutchpack died in a shower of molten plastic.


However... I'm getting a smell from under the bonnet that started when I switched on the aircon yesterday to defog the front windscreen. The A/C could be heard to 'clunk' in and then 'clunk' out again putting load on the engine at idle.

Pretty much straight away I was getting the smell of burning plastic and/or the smell of burning electrics.

Out of curiosity I unlocked the OBC and ran the voltage check - I was getting (bearing in mind windscreen wipers, rear demister, fan and headlights were on) about 12.4-12.5 volts (idle) 14.5-14.8 >2k RPM

Now I know the v8's idle really low, so it doesnt really surprise me that much - it would rebound to 13.8 at idle unloaded. Does anyone know if these figures are correct?

Next question! Is the 540 fitted with an auto tensioner on the A/C belt? could it just be the burning smell is the belt slipping rather than the clutch pack starting to self destruct?

Any pointers would be really helpful guys :)

EDIT: would running the compressor with no gas cause it to seize up?

[colo525i]

The voltage numbers don't seem entirely out of line, and it did recover by 2k, so that should be ok.

My 525 has an auto tensioner you loosen with an allen key to replace the belt. Try and pinpoint that smell, it will certainly lead you to your failure.

Yes, running w/o refrigerant will nuke the compressor, but the system has safety switches to prevent it from running without enough pressure.

[whiskychaser]

Okay, so this happened on my last E34 - the A/C compressor seized and the clutchpack died in a shower of molten plastic.


However... I'm getting a smell from under the bonnet that started when I switched on the aircon yesterday to defog the front windscreen. The A/C could be heard to 'clunk' in and then 'clunk' out again putting load on the engine at idle.

Pretty much straight away I was getting the smell of burning plastic and/or the smell of burning electrics.

Out of curiosity I unlocked the OBC and ran the voltage check - I was getting (bearing in mind windscreen wipers, rear demister, fan and headlights were on) about 12.4-12.5 volts (idle) 14.5-14.8 >2k RPM

Now I know the v8's idle really low, so it doesnt really surprise me that much - it would rebound to 13.8 at idle unloaded. Does anyone know if these figures are correct?

Next question! Is the 540 fitted with an auto tensioner on the A/C belt? could it just be the burning smell is the belt slipping rather than the clutch pack starting to self destruct?

Any pointers would be really helpful guys :)

EDIT: would running the compressor with no gas cause it to seize up?
Last things first: from memory if you have no gas the a/c doesnt kick in does it? If you get someone to press the button you can soon see if the clutch kicks in-or is it buried on yours? Putting a/c on on mine increases rpm by about 100 so that could be a clue. Auto tensioner I cant help with - but I know mine has one. (They look like a little shocker if you arent familiar) Your voltages seem spot on to me. You would normally hear belts screaming before they fail but check them anyway. If you see any black goo on them, then FFS dont touch it (HF risk)

[Ross]

Voltages semm allright.
Is your system overcharged with refrigerant OR oil? Sounds like the compressor is working too hard.