RE: <e28> AC death

[Alex Fadeev <Alex.Fadeev@xxxxxxxxxxxxxx>]

Tom,
	Here is my experience from trouble shooting AC problems on E30.
Some/most of this should apply to E28.

> The switch is on, the power is going to the compressor. 

	Not necessarily.
	First of all, start by checking the fuse (there are no relays in E30
AC system).
	If you have an ETM for E28, check the 12V out of the switch to make
sure the switch is working (need to know the color of the out wire). 
	Next the power would be routed through the evaporator switch
thingie. I never found it on my car so I can not be more specific. It should
be listed/diagramed in the ETM.

	Now onto the engine compartment. The 12V first goes through the
pressure switch to make sure there is Freon in the system. Look upstream in
the wiring from the compressor harness. One of the wires should lead you to
a switch right next to the dryer (the thing in front of the RHS headlights
with a tiny glass window for checking freon charge(bubbles)). 
	There should be 12V on the wire _to_ the pressure switch (with AC
button ON) and 12V coming _out_ of the switch (to compressor) IFF the system
is charged. 
	If there is no 12V coming out of the pressure switch to compressor
then you are out of R12 and have a leak in the system.
	If there is 12V out of the pressure switch and into the compressor
and the bubbles in the gryer's window are not moving then the compressor is
dead. 

	If there is a leak in the system you will need to replace the
leaking part (evaporator = $120, hoses? condenser?). If the system has been
empty for more
than one hour, the receiver drier must also be replaced. 
	This is a good time to make a switch to R134a. For E30's, BMW sells
a R134a conversion kit consisting of a R134a friendly dryer, different
pressure switches and a couple of adopters for $200. Older pre '87 E30s
required two additional hoses ($150 and $65 each from the dealer!!!), so
double check to make sure you get the right parts. The same conversion kit
can be had from aftermarket sources (try Kenn Sebesta 1-888 522-0271) for
$100. Actually, _all_ parts for the AC system from the aftermarket sources
will be at least 1/2 the price at the dealer.
	

> I can hear the
> switch click on and off when the temp switch is moved in the cabin.  I
> don't know, however, if the compressor is kicking in.

	Does your aux fan kick in? Do the RPMs rise a bit with AC on? If
not, the switch is dead.
	On E30s, the 12V to compressor come through the center of the three
wires on the wiring harness (with AC button ON and system charged).

	Most likely then not you have a leak somewhere in the system. Take
it to either a knowledgeable independent or you dealer to ascertain the
source of the leak (will cost around $100). 

good luck,
alex

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