Bad resistor = no low speed aux fan in 400E?
 

Just want to confirm that my thinking is correct here, based on Benzmac's advice on another thread --

Have noticed I haven't seen my aux fans run on low speed for a while, and I jumpered around BOTH of the 2 switchs on the receiver/drier, and no fan (ignition on, engine off). I believe this means the resistor is bad?

ALso, anyone have any advise for how to get to the resistor? Seems to be tucked under what I THINK is the horn for the alarm, and pretty close quarters there. Also, resistor is covered by a perforated metal plate so can't actually see the attaching screws.

Thanks in advance!

did you check the fuse too? had the same thing but from that thread i checked the fuse - turned out to be the problem...

Yep, fuse is OK . . .

Steve

My aux fans were not working this summer and the resistor was the problem. If the AC is on the fans should come on very quickly in stop and go traffic at outside temps above 70F or so...

You can change the resistor by removing the horn but a better way to go is to remove the headlight assembly - this greatly improves access to the resistor. As I recall the shield is held in place by an 8mm sheet metal screw.

My power input lead to the resistor just crumbled away when I touched it - looks like it had been getting hot for quite awhile - be prepared to replace the terminal lug and the ballast resistor.

BTW the aux fans made a noticeable difference in AC performance and engine temps in stop and go traffic.

Good luck

Tim

81 240D
93 400E
68 280SL
57&60 190SL parts cars

Thanks for the info!

Most of the time, when I do this, I run a new wire and install heat-sheilded shrink tube to protect this wire.
Also remember, the fuse for this is under the fuse box, you have to take off the screws to get to the fuse in the relay and update it to a 20a...

Didn't realize that . . . I thought the fuse on the outside of the fusebox was for the aux fans -- is there also a fuse inside the box?