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Is your AC system in good condition but not blowing cold air while
sitting at a stop slight?
Check if the aux cooling fan is running. The aux fan also serves
as a backup for the cooling system, when the temperature reaches
196F (91C) degrees the aux fan will spin in low speed, when the
temperature reaches 210F (99C) the aux fan should spin in high
speed mode. The aux fan located right in front of the condensor.
You can visually see if it's running by taking a look at your
kidney grill, it's right behind it.
If it isn't running, open the hood and remove the cover behind
the right headlight. There's a temperature switch located on the
right top side of the radiator.
Pull out the connector. The following information is from the
Bentley E34 manual page 170-4:
If the runs only when powered directly by the jumpered connector
amd hot coolant is circulating through the radiator, the radiator
switch is faulty. Use a new gasket ring (or crush ring) when replacing
the switch.
| Wires jumpered
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Test conditions |
Test Results |
| Violet/grey and brown |
Ignition ON |
Fan runs on low speed |
| Black/grey/yellow OR Black/grey and
brown |
Ignition ON |
Fan runs on high speed |
If the fan does not run when powered directly, check for battery
voltage at the switch connector with the ignition on. If battery
voltage is not present, check fuse #29 (low speed) and fuse #25
(high speed). If no faults are found, remove the relays and turn
the ignition on. Check for power at terminal 30 an terminal 86
of the relay block with the ignition ON. Fix any wiring faults
found.
If the fan operates only on high speed and no electrical faults
have been found up to this point, use an ohmmeter to check that
the fan resistor is not electrically open.
Italian for: the resistor might have crapped out. (This
would be the point where I'm not quoting the Bentley manual anymore.)
The resistor runs very hot which, I would think, makes it common
for them to blow eventually. The following write up assumes the
magna brand resistor, located at 4'o clock relative to the aux
fan as opposed to the Bosch brand resistor, located on top of
the aux fan (Bosch and Magna are NOT interchangeable).
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(I jacked my car up and put it on jackstands
to have some more manouverability, probably not necessary
though.) Take your license plate off and its holder and then
rip off the center front bumper cover.
- Locate the resistor.
The screws (if original) might be very rusty. I used some WD40
on them and actually ended up even breaking one of the screws,
use new screws for installation.
- Remove the current resistor and cut off its connecting wires.
Install the new resistor, I got mine for $34.95 at Bavarian
Autosport .
- When done with installing and connecting the new resistor.
Start the engine and turn the AC on to check if the aux fan
comes on.
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