Rear Defroster Not working

V
2008 CX-9 GT
My 2008 CX-9 GT's rear defrosting is not working, when I measured the voltage it's showing 11.34 volts almost everywhere except the upper area which reads 0 volts. I search almost everywhere I couldn't find anyone experience this before who post a tip on how to resolve this.

The repair guide says that it should read 0 to 11 volts as you move from negative side to positive source. The diagram provided shows horizontal lines and two vertical line which provide positive and negative source. But looking on CX-9 rear defroster is not same, it has multiple vertical lines and the upper area seems isolated.

I think there's a break on the negative source that's why it's reading 11.34 volts everywhere. I want to know how I can take out the plastic cover of the tail gate so I can see properly the wiring. Can someone share me a diagram if you have one how to do this?

I also appreciate any other suggestion, I may be looking on complex solution but the fix is right there and I'm not seeing it properly. I want to do it myself if I can as I want to save $$$ of cost taking this to dealership as my warranty already expired. In addition I noticed this after I took my car for 40K maintenance routine.

Thanks,

AB
 
V
2008 CX-9 GT
OK I finally manage to remove the internal garnish that covers the tailgate wiring of my 2008 CX-9 GT and I check the continuity of the circuit related to rear defroster (defogger). All wires, and the filaments of the window defroster seem to be all OK. The upper portion that I mention on my first posting seems to be part of the FM/AM radio antenna.

Using a multimeter and tin foil I measure the voltage from left to right reference to the ground. The repair guide says the voltage measurement should start 11V and go down to 0v or the other way around as you reach the end. But what I'm seeing is 14V reading (with the car running) anywhere I measure on the rear window defroster filament. Why I'm getting this reading? Is this the reason why the fog on my tail gate window is not clearing?

I hope someone can shade some idea.

Thanks,

Allan
 

helbigtw

T-Rav
L
PA
V
08 CX-9 GT FWD
Chemical interferance? Try cleaning the inside of the glass with just a damp rag. It does not take much for a short back there.
 
V
2008 CX-9 GT
Chemical interferance? Try cleaning the inside of the glass with just a damp rag. It does not take much for a short back there.
That's the first thing I did clean the rear window. After it didn't solve the problem that's where I start looking for something broken.


I'm thinking that the capacitor inductor combination used as part of the heating element circuit, somewhere there is failure causing both side to read 14V.
 
V
2008 CX-9 GT
Attached is the circuit diagram I found for CX-9 2007-2008 model. I did a voltage measurement on Point A and Point B as shown on the diagram both readings shows 14V while the car is running. If I don't turn on the car my battery will get discharge so quick that I need to jump start the car with external battery.

I'm sure something wrong here, as another document says that from Point A as I move the voltmeter prove towards point B the voltage should drop to zero or ground. Looking on the diagram if one of the capacitor is shorted it will feed 14V to the BLK side and actually shorting my electrical system to ground whenever I turn on the rear defroster.

Is it safe to bypass the noise filter circuit and attached the positive of 12V battery on BLK/YEL wire and negative on BLK wire on the diagram to test the filament. Of course I need to disconnect the filament from the noise filter circuit.

Any suggestion, comments?


Thanks,

AB
 

Attachments

V
CX9/2007
Maybe the relay is constant connecting. The defrog 30 A fuse is getting constant power and the only thing that is in between that switching is in relay. Take the relay out (R4 in the main-box) and measure whether it is constant connecting on between the 2 connectors that are located directly next to each other...
 
I have a 2007 mazda cx 9 and the rear window defroster is not working. The switch lights up and automatically turns off after 15 minutes. Looks like the fuse and the switch is good. I used a multimeter to check the defroster tab but wasnt getting any electricity. Any ideas?
 

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