Rear defrost inoperative

[wehan]

Can't get my rear defrost to work. When I press the button I hear a click but the lights don't dim like they used to and the frost remains on the rear window no matter how long the rear defrost is on. I get a very faint glow from my led test probe in the rear window, I also get this faint glow at the under hood fuse. Any thoughts as to where to start checking?

 

[Bass_Waves]

So its either lacking power or ground. Also I think the defrost is low temp. Have you checked the fuse first?

 

[YelloEye]

I'll test voltage on mine later today. But my lights don't dim when turned on and it works fine.

 

[wehan]

The fuse is good, when I pull the fuse and test probe the contact to for the fuse I get a very faint light in the probe. I believe it isn't getting adequate power before the fuse (I'm checking at the big square 40a under the hood) I switched out relays and nothing.

 

[YelloEye]

How much voltage are you seeing?

 

[wehan]

Ill have to go check, been having this problem for 2 years and I just now have time to mess with it. My headlights would dim know a split second and then the engine/alternator would react accordingly. Now I get nothing. 99% sure there is a bad connection or damaged wire but not sure where to look

 

[Bass_Waves]

U know what. The redline did that crap. I replaced the power steering motor. Problem went away. Check the EPs fuse in the engine bay. Don't ask why it what does it have to do with it. I did not figure out how its connected. But something is up with that. I know the pscm plays a roll. The power steering motor was drawing power and overheating. I had no messages nor lose of power steering. I knew the fuse used to blow. On a cold night I pressed the rear defrost. Lights would dim for a second. Dash too.

---------- Post added at 02:09 PM ---------- Previous post was at 02:08 PM ----------

Just a quick FYI. If you go into a che by dealer and complain you have steering issues. They replace the motor for free . Its a small wait time like 30-1hour. But free fresh motor.

 

[wehan]

Ok so there is no click heard from drivers seat.

I get 15.3v across the jump post and ground. I get 15.3v from fuse to ground. I get 13.2v across the rear window clips unhooked from the grid and I get 0v across the clips hooked up to the grid. I do have continuity from window clip to window clip so if I turn on the defrost I should at least have 1 active element but I have none.

Hope that all makes sense.

 

[YelloEye]

So it's supplying 13.2v at the contacts, but it's shorting somewhere when hooked up?

 

[wehan]

It can hardly power my led test probe across the rear contacts, I believe this to be an amperage supply issue. I think when I hook it up the grid absorbs the little power there is.

 

[Bass_Waves]

By grid you mean the small posts that connect the heat lines from the rear window?

 

[wehan]

By grid you mean the small posts that connect the heat lines from the rear window?

Yeah, the "grid" of heat lines on the rear window.

 

[Bass_Waves]

Hmmm. On the contact post. Check if it isn't cracked. Take the plug and try to tighten up the pin on it.

 

[wehan]

Hmmm. On the contact post. Check if it isn't cracked. Take the plug and try to tighten up the pin on it.

They look solid and have a good connection, cleaned up contact to as best I could with a wire brush, I think I was able to bend up the tabs on the plugs and have a good tight connection but still nothing.

 

[YelloEye]

I'll check mine when I get home. How many ohms are you seeing across the grid?

Of you hook up just the test lamp on the leads is it bright?

Just saw glowing fuse in the OP... wtf? Fuse box might have a short.

 

[Bass_Waves]

Unless that grid has a bad ground. I cannot see it not heating up.

 

[wehan]

Ok, so I rechecked everything. Here are some pics to hopefully clarify things.

I get .6ohm across the grid with everything disconnected from it.

Reference and ground connection check.

Fuse power in.

Relay power in (switch off as to not confuse this with the trigger power) this is power from the fuse.

Rear +

Rear -

In line amperage

---------- Post added at 03:58 PM ---------- Previous post was at 03:54 PM ----------

Just saw glowing fuse in the OP... wtf? Fuse box might have a short.

Disregard, the fuse wasn't glowing it was my test probe, I was posting from memory but now that I just checked it my test probe was bright so I must have had a bad ground on my test probe at the time.

 

[Bass_Waves]

Oooooooo so much better with pics. Short is to hot. Not getting full amps.

---------- Post added at 04:16 PM ---------- Previous post was at 04:14 PM ----------

I'm not toooo sure how the wiring is set up on our cars. For all I know there is another connector hidden that distributes power to rear of car. I need a wiring diagram . Also check to see where that wire leads to. Also lift up the bottom seats. Take em out. There is wiring going thru there. I know I seen it way plenty of tines.

---------- Post added at 04:17 PM ---------- Previous post was at 04:16 PM ----------

That wire even getting small amount of current means that there is an open somewhere. Its not allowing full current to flow. It may actually be grounding itself out on chassis. Or wire may be broken inside the seal.

 

[wehan]

I think the wire is damaged somewhere or there is a bad connection somewhere, if it was a short it would pop the fuse?

 

[Bass_Waves]

OK. Found somethig. Pull the small little door on passenger side on the kick panel. Like sit Kk passenger side and bottom left is a panel. Pull it. Check the wiring to the BCM and check the fuses for the HVAC. Report back.