Hi there,

Recently I have been some probelms with the AC on my E36 316i, it's on a 97 plate with the digital A/C unit.
Initially the problems starting off with the heater speeding up and down all by itself, to remedy this I replaced the output stage resistor.
Only 2 weeks ago I replaced the microfilter at the back of the dash and today had the A/C coolant checked.

The coolant level checked out OK, but the A/C still does not seem to work as it should. When switched on the air does not cool and I never get the cold air experience.

The mechanic that checked out the A/C noticed that the clutch was not kicking in as it should and the big fan not coming on as well. He seems to think this could be related to a dodgy relay. The problem is that I don't know which relay or fuse controls the A/C clutch assesmbly.

Any idea's or resources I could look up to get this sorted once and for all!

Thanks

Naz

Find another mechanic. You can't make a static check of the refrigerant. The compressor has to be operating.

The A/C fuses will be found in the fuse box, of all places. If all fuses are ok, you'll need a voltmeter, a wiring schematic, and a set of A/C gauges to continue.

There is actually no way of knowing exactly how much refrigerent there is in the system. You can approximate it by reading static pressures, but this tells you very little. Static pressure should be close to ambient temperatures on both sides of the system if the system is even close to having a full charge. And if the compressor isn't engaging, I would have the static pressures checked. Chances are the pressure is low and the system should be evacuated and then recharged.

Thanks for the suggestions...

As for the mechanic, well he did use a R134A gas container and rigged up two guages, the first guage was connected to the inlet of the A/C system, without filling in any coolant, this guage read a level of 40-50. The red guage was not used as this is used to fill the system with R134A in liquid form?

Anyway I managed to get hold of electrical schematics all 600 pages of it from the www yesterday and tracked down the relay. Luckily I have a accident damaged mashed up '96 318i coupe. Pulled out relay from this and checked the numbers on the unit and tried it out. This however has not cured the problem, I am inclined to try out the clutch from the 318 to see if this cures it.
I suppose I could take it into the stealers to get them to check it out!

Thanks for all your replies

I am inclined to try out the clutch from the 318 to see if this cures it.


Or you could just test for voltage at the clutch connector. If 12 volts is present, the clutch is faulty. If not, something else is, as mentioned previously. Just guessing here, enough refrigerant has leaked out that the low-pressure cutout switch is open, preventing the compressor clutch from powering up. It's easily tested with a voltmeter. Jumping the switch should get it to operate, so should adding some refrigerant. Then the system can be fully charged. At that point you can check for a leak which will be expensive to repair, or just see how long it lasts before needing another recharge. Make sure the electric fan operates when the compressor clutch is engaged. Fix it if it isn't.