1991 W126 rear defrost defogger switch question
 

My wife's 350SDL has an issue with the rear defrost. I installed a new switch because the old one would not light up when pressed. The new one worked as intended but it seemed as if the timer would not turn off the switch/light. It would go out when you rocked the switch to the lower position. Now, the new switch will light up when rocked to the upper position, but will go out as soon as you let go of the switch.

Any ideas on this situation? Everything else works except the rear defrost switch. I do not drive the car on a routine basis, so I am not sure if the rear defroster works even though the light goes out when you let the switch go.

Thanks

I know there are some long time 126er's out there that have experienced this before?? Is there a relay that controls when the switch comes on and how long it stays on?

For late 126s, the switch is just a switch. The brains are in the N10 combination relay in the fuse box. Maybe early 126s have a different arrangement and you have the wrong switch.

Sixto
87 300D

Thanks Sixto.

Would the relay control when or how long the switch lights up (stays on)?

Yes. The relay sets the defroster for 30 minutes and powers the bulb in the switch. Do you know if the defroster is powered even if the bulb doesn't light? Maybe it's just a bad bulb contact at the switch.

Sixto
87 300D

I am not sure if I have power to the rear window, even though the light will not stay on. I will check this tomorrow. I have ordered a relay. I will share my findings.

Thanks

Update on rear defrost
 

I installed a new flasher. Now the rear defroster works correctly. The light comes on when you let go of the switch and it times off. I guess I had issues with the controller in the flasher.

HI MPH
my defroster switch behaves the same way,so you installed a new flasher? as in emergency flasher/turn signal flasher? can you provide me some details please?

Cheers

Kenny

124s and later 126s used a combination relay that handled turn signal and defroster timer in one package. It is in the fuse/relay box, tag N10. They actually install a dummy clicker coil in the cluster, or you would not hear your turn signal, since the relay is under the hood.

123s and early 126s had a defrost timer behind the cluster and a turn signal flasher under the center cluster.

If your 126 fuse box is recessed into the fire wall you have the early version. If your fuse box is a large black enclosure under the hood you have the later version.

A dummy clicker? I learned something new. Cool!