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RE: E30 A/C and Aux fan question
TJ Noto <tjn@domain.elided writes:
>The aux fan is supposed to blow ANYTIME the A/C is on to prevent overheating
>and of course has two speeds when the coolant temp reaches 196 and 210
degrees >F respectively. It does not ever come on under normal conditions,
nor does it
>come on after the car is turned off and is sitting still. Even in the very
hot weather >(95 >degrees) we've been having lately. <
TJ;
Sounds similar to a problem I experienced with the Aux Fan on my 84 7-series.
It looks like the configuration is nearly identical (my AllData disk only
goes up to 84). I finally discovered a loose electrical plug near the two
temperature sensors in the left sideof the radiator, a simple male/female
blade connector, each on a single wire. There also was a small round device
in the one line, I assume either a capacitor, diode, or a fusible link. Once
I reconnected this plug, the fan works fine with the AC on.
Keep in mind when you are diagnosing this stuff, that the realy contact
sockets are "hot" all the time, if you jumper in the socket between where pin
87 and pin 30 of the relay plug in, the fan will run (relay K1 normal speed,
relay K6 high speed) even with the ignition off. However the sensing lines
to the temp switches in the radiator itself are only "hot" with the engine
actually running.
These switches are fairly simple to check, especially if they are mounted
high in the radiator (mine are down low and require a major drain, which is a
major pain). Remove the switches, grab an old sauce pan, an ohm-meter and
one of grandma's cooking thermometers. Attached the ohm-meter leads (a
continuity checker will work) to the switch contacts, drop the switch and the
thermometer into the pan with water and heat on the stove. When the water
gets to the rated temperature, the ohm-meter should read zero or close to it.
If the budget allows (about $20 ea at the dealer), just buy new ones and
check
them a few times before you put them in. There is a lot of variable
tolerance in
these, and they fail often in the first couple of heat/cool cycles. Besides,
checking new ones keeps the kids from whining about that ethelyn-glycol
taste in their spaghetiO's! :-)
Hope this helps.
Kevin '84 745i
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