2005 ION2 rear defrost not working
 

I'm trying to figure out why the rear defrost does not heat. I've checked the fuse and it is fine. I do not get any current at the two window leads when the defrost is switched on. The panel indicator light comes on but no juice.

My first thought was that the switch may be bad but I find it odd that the indicator light comes on.

Next thought is a physical break in one of the wires. Is there a published wiring diagram for this? I'd rather not just start taking panels off trying to trace the wires.

Or does someone have another idea where the break could be.

Thanks.

Wiring diagram or not you'll still have to trace down the problem. Go to the store and buy a service manual for your car. That would be at an auto parts store.


Latitude:-32.7766 (32° 46′ 35.76″ N)
Longitude:-79.9309 (79° 55′ 51.24″ W)
who could that be?

,and you know for a fact that the relay and fuse are in working order?

RjION - Ah...didn't catch that there was a relay. I'll check it out too.

I'll post back if that isn't the fix.

Thank you.

How about posting back even if that IS the fix. That way, maybe the next person will be able to remedy the problem quickly.

It would be interesting to find out just how it was determined that there was no electrical power at the two window leads .....

You are the rooptech

I used a DC volt meter. No current and no continuity with dashboard switch on. I checked with the two leads connected to the grid and with both of them off.

I have a new relay but I don't feel like braving the rain to switch it out. I'll post the results after the weather dries out.

The reason I asked the question, is that I too had a problem with my rear window defroster (wife's car). Granted, my wife's car is an '09 Aura, but I suspect the system works pretty much the same.

Turned the ignition switch to the "RUN" position without starting the car. Turned off radio and other noise-making devices. Pressed the switch, and was able to hear the relay "click". Measured across the tabs on the window --> nothing.

Examined the window carefully where the wires attach to the tabs (looking for a break in the window grid) --> looked good to me. Measured for voltage again, only this time from the window tab on the driver's side to the frame of the car -- VOILA! 12 volts!

Remeasured across the tabs, and got a reading of zero --- what the heck? Repeated the measurement from the tab to chassis ground -- 12 volts. After a bit of head scratching, decided to measure from the tab on the passenger's side to the chassis -- and got a reading of 12 volts also !?!

Disconnected the wires from the tabs, and measured from each wire to the chassis. On her car, the driver's side wire was 12 volts, and the other side was zero. It finally became clear -- there was a break/disconnect in the wiring from the defroster back to chassis ground. Rather than try to locate the break, I just obtained a sire of similar size, and ran it from the tab to the chassis --> problem solved!

I don't think I've ever turned on my rear defogger.

To RjION --

humpf. In your neck of the woods, I wouldn't doubt that a bit .... LOL

Good observation. Didn't consider that the break could be on the ground side. I'll check that too.

/When it dries out that is...we've had nearly 4 inches of rain in the last 48 hours with another inch or two on the way tomorrow.

Looks like the relay was good. I replaced it and the defrost still doesn't heat up. I'll check the electrical a bit more carefully and report back.

Anything?

Sorry - it's not at the top of my to-do list at the moment. I hope I'll have time tomorrow afternoon to check out the grounding issue and maybe a few other things. Look for an update on Sunday.

-T

OK...I had some time to spend in the car with the volt meter. I checked for 12v to ground from both leads into the rear defrost. I got nothing. I then checked for continuity from both leads to ground. I got it on the passenger side but not on the driver side. I figure that is the cable from the battery that runs through the relay. So the break is somewhere on that side.

I attached some short wires to each of the 4 connectors on the relay and extended up up an inch or so. This allowed me to check voltage across the relay. With the ignition set to ON I could hear the relay engage when I pressed the dash button for the defrost. With that ON I checked for voltage. I get 12v to ground from the relay when it is on. So far so good. However that is where things run aground. I don't know exactly which wiring bundle the 12v cable to the rear defrost goes through. I suppose I could detach the box engine compartment and manually trace it but I may muck up other connections if I do that.

That leads me back to the original question. Does anyone know what route that wire would take? Would I be able to access it from any other panels (or under the car) Where I could test it again?

Not having looked at the repair manual before is this something that it would have in it?