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Need help with rear window defroster on 1991 240 sedan - locating the relay?

posted by  keithostertag on  Mon Dec 5 16:44 CST 2011
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last visit: Tue Jun 17 15:10 CST 2014
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I remember from last year that my rear defroster doesn't work and hope to remedy that before I need it this year. There are several Brickboard discussions about 240 rear defroster problems, but most of them deal with wagons- mine is a sedan.

Just to be clear- my rear defroster switch on the dash is a momentary spring switch- press it once and it springs back into its original position. The switch light, of course, doesn't work. You can see in the attached photo that it has one yellow/blue and one yellow/red wire to the switch, with one yellow wire to one side of the lamp and two black wires from the other side of the lamp. How do you access those wires with a VOM meter? I don't see anywhere there is bare wire to touch with the meter lead tip.

I don't see any obvious wire leads at the rear window defroster itself. There is only some kind of what-looks-like a clip on each side, shown below in photo 2. Nothing obvious to my eye in the trunk.

I have checked that I have voltage on the right side of both fuses 11 and 12 when the car is running. No voltage there with the ignition ON to KPII without starting the engine.

Art Berstein posted a reply to a similar query a few years ago here:
http://www.brickboard.com/RWD/volvo/1381006/220/240/260/280/240_sedan_rear_defrost_problem_defroster.html

In it he says:

"would start at the relay, located near the driver's feet and identified by its large yellow and blue/black wires, plus smaller yellow-red, black, and yellow. Check for voltage with key on (in KP-II) at the blue/black wire. Turning the defroster switch "on" should then cause voltage to appear at the yellow-red wire and finally at the yellow wires, which run to the heating element. If you get nothing on the yellow-red wire, trace it back through the defroster switch to fuse #12 on a blue/yellow wire."

I can't find/identify the relay. Is it hidden under the carpet? Near which foot, which side? Is it hidden behind the console center side trim? Is it a small box-like component? Metal or black plastic? A good photo would realy help.

Also, to make things confusing, the Bentley manual says there is a "heated rear window time relay" at location 175 in number three photo below (page 390-3 in Bentley). Could this be related to the relay Art is refering to?

Also, what's the best way to test to see if the defrosted is actually working? You know, like before there's frost to get rid of ...

Thanks,
Keith
--
1991 240 Sedan B230F LH3.1 300K miles







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