No Rear Defrost

[Sun Dropsz]

I've had this car for about a month so I don't know too much about it. The rear defrost doesn't work at all. The orange light won't even come on. I've already ordered a new switch. The square box the clips into the dash with the defrost and emergency flashers. I don't know where to start. I'm thinking maybe it could be a cut wire or bad relay maybe.
1993 GT

 

[mikestang63]

It would help if you stated what year and model. Is it a 5.0 or 2.3 liter as wiring can be specific to years. here is a helpful link of schematics

http://www.veryuseful.com/mustang/tech/engine/#Diagrams

First thing is check Fuse 6
then use a DVOM and test the heating connector for power- check the metal strips that feed the power aren't broken off. If they are, they sell a metal paste to secure them back on
then look for any broken or scratched lines on the window for a break in continuity. put the leads on the DVOM on each end of each line and see if you have voltage running across them.
Parts stores sell the metal"paint" that you can brush on to fix the lines.
Then check the relay under the dash to the right of the fuse box

wiring schematic

 

[Mustang5L5]

There is a relay under the dash down by the clutch pedal. You'll need to use the above wiring diagram to trace outbyhe wiring.




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[Sun Dropsz]

It would help if you stated what year and model. Is it a 5.0 or 2.3 liter as wiring can be specific to years. here is a helpful link of schematics

http://www.veryuseful.com/mustang/tech/engine/#Diagrams

First thing is check Fuse 6
then use a DVOM and test the heating connector for power- check the metal strips that feed the power aren't broken off. If they are, they sell a metal paste to secure them back on
then look for any broken or scratched lines on the window for a break in continuity. put the leads on the DVOM on each end of each line and see if you have voltage running across them.
Parts stores sell the metal"paint" that you can brush on to fix the lines.
Then check the relay under the dash to the right of the fuse box

wiring schematic

I have a 1993 gt. I looked under the dash and I cannot find this relay for anything.

 

[mikestang63]

The relay is just to the right of the fuse box and mounted upside down behind the trim panel.Look for this

 

[General karthief]

It may have been removed by the previous owner for some reason. Look for a connector that matches the picture

 

[Mustang5L5]

This may help

http://www.stangnet.com/mustang-forums/threads/rear-defrost-relay-location.892522/


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[mikestang63]

It may have been removed by the previous owner for some reason. Look for a connector that matches the picture

 

[Sun Dropsz]

I looked and looked and never found it. I even took the seat out to lay down and look. The only disconnected wire I found was this one. I don't know what it is. It probably has something to do with the fuel injection system. But this car was converted to a carburetor.

 

[Mustang5L5]

That's not it.

This is it. to the left of the hood prop. It's bolted to the dash frame

 

[Saleen0679]

I looked and looked and never found it. I even took the seat out to lay down and look. The only disconnected wire I found was this one. I don't know what it is. It probably has something to do with the fuel injection system. But this car was converted to a carburetor.

That is the correct connector for the Defrost Control Relay. The connector/relay changed sometime in the 90's.

http://forums.stangnet.com/showthread.php?t=836969

 

[Mustang5L5]

Guess it did change out in later years

http://www.ebay.com/itm/1987-93-For...ng-Harness-Connector-Stock-Used-/181102642181

I can't seem to locate a relay that fits this harness though. All searching turns up the first version like I posted.