Troubleshooting Rear Window Defroster?
 

So I tried the rear window defroster for the very first time and it doesn't work. The little LED doesn't illuminate and the grid doesn't warm up.

I have vol 1 & 2 of the shop manuals but no electrical diagrams, plus the owner's manual. I did as much troubleshooting as I could but got nowhere. I'd appreciate any suggestions if anyone else has been through this.

Here's what I checked so far:

• Scangauge shows no DTC's
• Both fuses are good (#28 in BJB and #10 passenger side fuse panel)
• Connections to heater grid are good
• Have continuity through the heater grid
• Left side of heater grid is grounded
• No voltage on the right side of heater grid when I activate the switch

Shop manual makes reference to a "rear window defrost relay", but I don't know where it's located. Anybody know about this one?

Thanks for any help with this. I'll probably never need to use the rear defroster again, but it bugs me to know that it's not working, so I'm determined to fix it.

Re: Troubleshooting Rear Window Defroster?
 

The relay is in the battery fuse/relay box in the engine compartment. You could check if you have voltage at the fuse also.

Re: Troubleshooting Rear Window Defroster?
 

Bill,

I don't think this relay is in the BJB. There are 7 relays and 32 fuses in the BJB, but none of the relays are related to the defroster function. The relays are:

• Power sustain
• PCM power
• Injector
• Aux collant pump
• Motor/Electronic collant pump
• Foglamps
• A/C clutch

From the workshop manual the defrost relay appears to be in the Smart Junction Box (SJB) which has to be accessed through the "floor console SJB cover". That might be beyond what I want to attempt.

Good tip about checking voltage at the fuse. I found the FEH wiring diagrams on eBay for $5, so that is on the way and might help with this.

Re: Troubleshooting Rear Window Defroster?
 

Try rebooting, disconnect the battery ground more than 5 minutes.

GaryG

Re: Troubleshooting Rear Window Defroster?
 

I was using the diagrams from a 09'FE and the FEH are very different. I had to get load a driver to view electrical diagrams on-line, luckily the W98/XP Viewer worked with W7. Here's the diagram but I'm not sure how it's going to look in the post. Looks unreadable from the Preview Post. I've done this from my XP machine before in a different forum and they look good. Oh well, you have a book coming anyway.

Yes, the relay is in the SJB! Yes, the diagram needs some darkening and contrast for sure. Well, I tried... Okay, that's much better. :)


Attachment 2920

Re: Troubleshooting Rear Window Defroster?
 

Bill, thanks! That's a very useful diagram and I can do some voltage checking from there. My guess is the problem will be in the SJB and I really don't want to try removing that.

Gary, thanks for the tip on rebooting, and I'll give that a try. Will I lose any configuration data if I reboot? [Nevermind, found the answer in the owner's manual in the section about replacing the battery]

Re: Troubleshooting Rear Window Defroster?
 

I wonder if that was changed later on and placed in the box under the hood?