The switch for the rear window defroster in my 240 wagon does not hold in the "on" position. Consequently, the defrosting does not work. With the first winter storm, I would like to address this issue.. Any ideas where to start?

 

what vintage 240? most of them on 2/7/9's were mechanical on/off switches, but some are momentary on, and had an electronic timer (but I'm really not sure if ANY 240's ever got this)

if its supposed to be a mechanical switch, its remotely possible you could disassemble the switch and degunk the mechanism, but I've only had luck repairing Mercedes switches, Volvo ones usually need replacing. junkyard, or someone parting out another similar car.

 

The wagon was born in 87. The switch seems to be identical to the emergency lights one, that is next to it. It simply does not hold in the "on" position. Also, there is no light when I force it into the "on" position... Is it easy to get that particular piece of the dash out?

 

Our 240 has wandered off with my daughter to Portland, so I can't go out and look to remember where it is, but IIRC, those switches pop out pretty easily.


wait. the 87's DO have a timer relay, the button is momentary contact. the wiring diagram is remarkably vague about that relays location, the arrow points to somewhere under the driver side dashboard, maybe just left of the steering column.

its a 4-pin relay...

pin 31 is ground (black)
pin 86 goes to the switch (yellow-red)
pin 87 goes to the light in the switch (yellow) and to the rear window (also yellow)
pin 15 is power from fuse 11 (blue wire) (fuse 11 is also the overdrive fuse).

the switch gets power from a blue-yellow wire to fuse 12 (which is also the air conditioning fuse)

VADIS says this relay is part number 1324675.

if you locate the relay and you have a volt meter or test light, I would unplug it, turn the ignition on, verify there's power on pin 15 of the socket, and verify that if you push the button on the switch, there's power on pin 86 of the socket. now, key off, plug the relay back in, key back on, push and release the switch and see if there's power if you stick a probe into the back of pin 87 (the yellow wire). in 10-15 minutes, that pin 87 power should turn off.