Heated rear window not working.

[shadow400]

The heated rear window in my 1989 525i has suddenly stopped working.
When i press the switch it lights up so there is power getting to the switch.
I have checked the fuse which is ok, but when i put voltmeter on the connections to the window there is no power.
Nothing has been done to disturb anything so god knows why it`s happened.
I have to go out for a couple of hours so any reply`s and idea`s will be much appreciated.

[525SEI BRIT]

Have you checked all heating elements running along the glass that usually burnout. Short of that, sounds like a short connection or a corroded wire somewhere between the switch and window. Afraid you’ll probably just have to follow and check the wiring-loom piece by piece.

[Jr ///M5]

Did you look under the rear seat, drivers side. There are more fuses and relays under a black cover. I found one on my old 535 that was melted, replaced it and the defogger worked fine.

Jr

[Javier]

Did you also check Defogger relay K13 (K13, the one standing alone just besides the relays K15 and K11 that are side by side. K12 is at the other extreme of the box).

Also, is the generator working OK, the un-loader relay will cut power to the defogger relay if alternator fails to generate.

If you play with a meter at the defogger relay socket, you may find what is going on.

Power from F46 is at pin 30, power from un-loader relay is at pin 85, ground signal from climate control (defogger request) is at pin 86, and rear defogger heating elements are connected to pin 87.

Javier

[632 Regal]

Javier, my rear defog is always on but the light never goes on, would that simply be relay #k-13 or should I check something else?

[Javier]

The light is a LED just as the other two buttons, and the climate control illumination. If you have the chance, just unplug the connector to the Climate control Switch Module (X18151, Black 10 pins) and check the module for a LED from 6 to 7, from 6 to 5, from 6 to 3 and from 6 to 1. Switches (buttons) are from 9 to 2, 10 to 2 and 4 to 2. There is also three LED's in series with a resistor from 8 to 2. If your tester has a diode check, you can check LED's having 1.4 volts forward, open circuit reverse, if not, check resistance just as you do for a diode. The series LED's will need more than 4.2 volts source to test, not all the continuity testers feed that much, you can array 4 x 1.5 batteries and fed from 8 (+) to 2 (-) they should light up, even dimmed.

All this LED's are powered and controlled from the Integrated Climate Regulation Control Module IHKR/F3, if all the LED's are fine, the switches tested fine, and the other buttons LED's work fine, guess you have a problem inside the IHKR/F3 (doubt it).

If the defogger is permanently on, no mater the status of your switch, either you have a short circuit to ground in the IHKR/F3 output controlling K13 coil, you have a stuck close contact in the K13 relay, or some sort of short circuit in the wiring (doubt it). Just pull out K13 and push it back in, if you feel it clicking, there is a Rear Defogger request signal to the relay, if no clicking, check for open circuit between pin 30 and pin 87 of the relay, if continuity there, the power contacts of the relay melted close, if checks OK (Open circuit), and you have no click when put back in the socket (just to confirm), pull it back out and check voltage to ground from socked hole corresponding to pin 87 of relay, there should be 0 Volts, if not, there is a short-circuit to battery voltage somewhere from the defogger relay to the heating elements (doubt it as you would have notice other symptoms). Hard to tell who is the culprit, Anti-Theft, antenna amplifier?

If you have a click at the relay, then check if the click disappears when you unplug the IHKR/F3 connector X18157 (Blue 26 pins). There are two of them; you are looking for the one with a Brown/Yellow wire at pin 20. If the click is still there, you have the wire short-circuited to ground somewhere between the IHKR/F3 module and the rear seat fuse/relay box, the Brown/Yellow wire turns into a Brown/Orange one before reaching the K13 relay, check the wire from X18157-20 to K13-86b. If the clicking disappears when you unplug the X18157 connector from the IHKR/F3 module, then; there is a problem in the module as it is requesting defogger operation without the switch telling it to. Guess you did debug the proper operation of the switch.

Just let us all know what did you find out when done.

Javier

Edit: Links to missing pictures
http://www.bimmer.info/forum/attachment.php?attachmentid=851&stc=1
http://www.bimmer.info/forum/attachment.php?attachmentid=852&stc=1

[632 Regal]

it stays on and the switch doesnt light or turn it off. I will check into this during the week and see if I can locate the culprit. thank you!

[Scott C]

The light is a LED just as the other two buttons, and the climate control illumination. If you have the chance, just unplug the connector to the Climate control Switch Module (X18151, Black 10 pins) and check the module for a LED from 6 to 7, from 6 to 5, from 6 to 3 and from 6 to 1. Switches (buttons) are from 9 to 2, 10 to 2 and 4 to 2. There is also three LED's in series with a resistor from 8 to 2. If your tester has a diode check, you can check LED's having 1.4 volts forward, open circuit reverse, if not, check resistance just as you do for a diode. The series LED's will need more than 4.2 volts source to test, not all the continuity testers feed that much, you can array 4 x 1.5 batteries and fed from 8 (+) to 2 (-) they should light up, even dimmed.

All this LED's are powered and controlled from the Integrated Climate Regulation Control Module IHKR/F3, if all the LED's are fine, the switches tested fine, and the other buttons LED's work fine, guess you have a problem inside the IHKR/F3 (doubt it).

If the defogger is permanently on, no mater the status of your switch, either you have a short circuit to ground in the IHKR/F3 output controlling K13 coil, you have a stuck close contact in the K13 relay, or some sort of short circuit in the wiring (doubt it). Just pull out K13 and push it back in, if you feel it clicking, there is a Rear Defogger request signal to the relay, if no clicking, check for open circuit between pin 30 and pin 87 of the relay, if continuity there, the power contacts of the relay melted close, if checks OK (Open circuit), and you have no click when put back in the socket (just to confirm), pull it back out and check voltage to ground from socked hole corresponding to pin 87 of relay, there should be 0 Volts, if not, there is a short-circuit to battery voltage somewhere from the defogger relay to the heating elements (doubt it as you would have notice other symptoms). Hard to tell who is the culprit, Anti-Theft, antenna amplifier?

If you have a click at the relay, then check if the click disappears when you unplug the IHKR/F3 connector X18157 (Blue 26 pins). There are two of them; you are looking for the one with a Brown/Yellow wire at pin 20. If the click is still there, you have the wire short-circuited to ground somewhere between the IHKR/F3 module and the rear seat fuse/relay box, the Brown/Yellow wire turns into a Brown/Orange one before reaching the K13 relay, check the wire from X18157-20 to K13-86b. If the clicking disappears when you unplug the X18157 connector from the IHKR/F3 module, then; there is a problem in the module as it is requesting defogger operation without the switch telling it to. Guess you did debug the proper operation of the switch.

Just let us all know what did you find out when done.

Javier

Edit: Links to missing pictures
http://www.bimmer.info/forum/attachment.php?attachmentid=851&stc=1
http://www.bimmer.info/forum/attachment.php?attachmentid=852&stc=1

Just wanted to say THANKS! Javier - this writeup just made a 3 hour job - 1 hour. My rear window was not heating and was very quickly able to diagnose F35 (Buried under the keyless entry box) as bad.