1G rear defrost/heater issue

[blizz99]

hey. i just got back from iraq and noticed that my heater and rear defrost isnt working. that leads me to believe it's a fuse/relay but i checked the one on the driver side in the interior and the 30 and 10 are good. does anybody know if there's any other fuses or relays? if anyone has any ideas please let me know because i cant drive it due to it fogging up and i cant see. oh yea, it's a 92 talon tsi

 

[mrxios]

So the in-glass rear defroster is not working (not getting hot) and the heater blower is not blowing, are those the symptoms?

There is a 40 amp sub-fusible link in the engine compartment that provides the juice for the rear window defroster. Labeled R. DEF.

There is another 40 amp SFL in the same box labeled BATT, it appears to go to the blower motor through the 30 amp passenger compartment fuse you checked. Its goes to other stuff as well so if it was blown other things wouldn't work.

The 10 amp in the passenger compartment you checked (#3) is common to heater circuit and rear defroster circuit. It controls the coil on each of the device relays to allow the large current circuits to supply the devices.


If the symptoms i described are correct and the 10 amp fuse is good, you more than likely have two separate problems.

The 40 amp SLF for the heater blower motor is probably fine, I would probe the blower heater motor connector coming from the wiring harness for 12v with the ignition on and the fan switched to high and go from there.

Does the light indicating its on light when you engage the rear window defroster?


http://www.dsmtuners.com/forums/frequently-answered-dsm-questions/310956-1g-2g-fuse-box-diagrams-cover-diagram-fuses.html

http://members.shaw.ca/dsm.1000q/Engineprimer/1G/relaybox.htm

 

[blizz99]

ok, so i replaced the relay right above the interior fuse box and now the heater works but the rear defrost doesnt work still. the light for the rear defrost doesnt even come on. i checked the fuse in the engine bay and it's good. any ideas?

 

[mrxios]

Link:

90-91el


Page 8-297 and 8-299.

It appears the "on" indicator light gets its power from the contacts on the rear defroster relay. The coil on that relay is triggered from the rear defroster timer, which is activated by the dash switch.

So, not with standing a loose wire,I would say one of those components is bad provided the 10 amp and the 40 amp SFL are good.

The page 8-299 describes location and testing of the components. Maybe re-seating them would help.

Hope this helps.

 

[Jody Bailey 1983]

Mrxios,
Thank you for the link. This information was also helpful for my ‘92 gsx. I repaired the defroster connection to the rear window and my battery kept dying. I pulled the fuse under the hood and and I was stuck until I found this thread with your link.

After pulling the switch to change it I discovered that it was not hooked up! I changed the switch and timer to no avail. Lastly I discovered that there is a relay under the hood directly behind the battery. I replaced the relay and my defroster now works! I am fortunate to have a parts car to scavenge these parts, but the link you provided gives instructions on how to test each of thee components.

Thanks again!