2005 Tahoe rear defogger not working

[Opus62]

Hi guys and gals.

I have a problem with my 2005 Tahoe rear window defogger. The wires are connected but no power there. The mirrors defog/defrost quite nicely but nothing at the back. I have not started much diagnostics yet so I am looking for any info regarding common issues that others may have had.

 

[JochenWoern]

Hi guys and gals.

I have a problem with my 2005 Tahoe rear window defogger. The wires are connected but no power there. The mirrors defog/defrost quite nicely but nothing at the back. I have not started much diagnostics yet so I am looking for any info regarding common issues that others may have had.

Having exactly the same issue and could never figure out what was wrong.

Living in Northern CA, I accepted the fact and decided to live with it as I never get ice on my windows.

 

[Larryjb]

Sorry to resurrect an old post, but did you every find the problem?

I seem to have 12V when I remove the plug, but it drops to 0 as soon as I connect it to the grid. I'm suspecting a bad connection in the wire leading up to the plug, but I cannot find any wiring diagrams that show the routing of this wire.

 

[Yates_III]

Barn doors or Lift gate? Asking for troubleshooting reasons. If you have a lift gate w/ a wiper, see if the wiper comes on.

I had the same problem where my rear defrost and my rear wiper wouldn't work. Ended up being the connector plug. Cleaned the connections with electrical contact cleaner, plugged the connector back up and haven't had an issue since.

 

[Larryjb]

Lift gate. Thanks Yates. I'll check into that. I didn't realize there was an actual plug in the lift gate.

 

[Yates_III]

No problem Larryjb. There is a rubber boot that runs from the lift gate to the body of the truck. You can pull the trim panel that holds up the headliner, GENTLY pull down headliner to access the plug assembly. Spray it with the cleaner and inspect for broken connections and hopefully that clears up your issue.

Good luck!

 

[Larryjb]

Thanks again Yates. I thought the connector was actually in the liftgate and was about to look there. I'll look behind the headliner and see tonight.

 

[Larryjb]

I found the connector, and the defog wire in the connector was badly burned. Unfortunately, I don't think that's the end of the trouble. When I put the volt meter on the good end of the wire, I still only got 6V which means there is a bad connection further up the line.

So, what is the next connector up the line?

 

[Yates_III]

I was hoping that wasn't the case for you...sorry to hear that.

I will have to look on the wiring diagram to see where the next connections are upstream from that rear connector.

Do you have rear HVAC controls and/or moon roof?

 

[Larryjb]

I do have rear HVAC contols and moon roof.

Are you using the wiring diagrams from the FSM?

 

[89Suburban]

I found the connector, and the defog wire in the connector was badly burned.

Interesting!!!

 

[Larryjb]

Here is a picture of the affected connector. Once I removed the burned out terminal, I measured the voltage and got 6V or so. I'm going to check at the relay at the engine bay fuse box.

 

[Larryjb]

Finally found the wiring diagram I needed. In case anyone else has the same issue:

 

[Yates_III]

That was the diagram i was referring to. As you mentioned, i would check the voltage at the "front" of the system. I cannot remember off the top of my head what the voltage is and what the drop across the system.

I believe on moon roof tahoes the harness runs down the drive side kick panel, under door seal panels, through the jack panel, and up the D pillar. I am not 100% sure on the actual location.

 

[Larryjb]

I've got a good 12v at the fuse. The next place to look in the connection at C1 as that is the only connection between the the fuse block and the connector at the the lift gate.

 

[CFD Jerry]

I was just going to say what I read above.. Clean your contacts with contact cleaner.. Worked for me

 

[Larryjb]

I was unable to clean the female terminal adequately. When I tried to remove the terminal from the connector, the terminal actually pulled out from the wire because the plastic connector was blackened and melted around the terminal. I will probably need a new connector for the female side. I can fairly easily clean and save the male side.

However, I do have more issues than the connector at the lift gate because I still have only 6V at the wire going to the connector. The next step is to inspect the connection at the fuse box in the engine bay. That involves a little more work!

 

[Larryjb]

okay, time to eat a little crow here. The ground I was using was not a good ground and was fooled into thinking I had a problem farther upstream.

I measured the resistance between the fuse box and the heater wire to the rear window and got zero resistance. I only have to fix the connector at the lift gate.

 

[HiHoeSilver]

okay, time to eat a little crow here. The ground I was using was not a good ground and was fooled into thinking I had a problem farther upstream.

I measured the resistance between the fuse box and the heater wire to the rear window and got zero resistance. I only have to fix the connector at the lift gate.

Good double check to catch yourself. I was going to ask about your ground. I usually run a wire from the - battery post when I'm checking stuff like that for that exact reason.

 

[Larryjb]

I thought the ground I was using was good because I checked for continuity between the heater grid ground side with the ground I was using for testing and had zero resistance. I guess it was a "flakey" ground. Anyway, I now have "less" work to do. I'm going to replace the plastic connector, but reuse most of the terminals. Most of them can be removed and transferred to the new connector.