another aux fan no go
 

the '85 SD's aux fan runs fine connected direct to battery but not otherwise.
Yes i shorted the temp switch on the drier, yes i checked the fuse (replaced with new) yes checked relay (replaced with known good one).
Any further things to check? Thanks.:confused:

Try the other temp switch
 

I believe the temp switch on the drier controls the compressor. The temp switch that controls the fan is the one on the thermostat housing.

I believe the pressure switch on the drier also controls the low speed fan setting and the one on the thermostat housing controls the high speed fan setting. There should be two relays, low speed and high speed.

John

The drier has two switches, one pressure switch that controls the compressor. The other is for the Aux fan.

You can remove only temp switch with out loss of freon.

Closing in on it
 

I see up to 12.7 volts at the fuse. But only between 9.7 and 10 volts at the drier spade connection (before the drier) and between 9.7 and 10 volts at the socket where the fan plugs into. I assume that's why the fan won't run. Any idea what might be causing that?

Check continuity across the low speed resistor.

Sixto
87 300D

No continuity
 

across the resistor, it seems. The place where they put it you'd think they thought it would outlive the car and never need replacing. Any tips on how to get it out and a new one in?

If it's behind the headlight, easiest to pull the headlight.

Sixto
87 300D

Oops, I guess from the other thread yours is under the brake booster. I don't know how to get to that other than with a a Philips bit on a u-joint and really long socket extensions.

Sixto
87 300D

resistor replacement
 

Looks like the 124 uses the same resistor. Can the beige part be unclipped/unsnapped from the black bracket or do you have to remove the whole thing?

Pics show what 126 owners have to deal with to get to it:(

You might be able to pry the bracket open but I doubt you can do it with the bracket screwed in place.

Sixto
87 300D

Well, anyway, your bad resistor diagnosis was spot on. Ran a wire between the two terminals to bridge it and the fan started right up. Thanks for that.

Unfortunately have bigger fish to fry now: Just lost 2nd 3d and 4th gear while testing the kickdown on the highway. Time to start a new thread. :eek: