No Rear Defrost

Sun Dropsz

New Member

Nov 25, 2016

22

2

3

Huntsville, Alabama

Nov 26, 2016

#1

• Nov 26, 2016

• #1

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

 

Last edited: Nov 27, 2016

mikestang63

SN Certified Technician

Aug 27, 2012

11,606

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In the garage

Nov 26, 2016

#2

• Nov 26, 2016

• #2

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

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

43,355

18,101

224

Massachusetts

Nov 27, 2016

#3

• Nov 27, 2016

• #3

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

New Member

Nov 25, 2016

22

2

3

Huntsville, Alabama

Nov 27, 2016

#4

• Nov 27, 2016

• #4

mikestang63 said:

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

Click to expand...

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

 

mikestang63

SN Certified Technician

Aug 27, 2012

11,606

8,859

214

In the garage

Nov 27, 2016

#5

• Nov 27, 2016

• #5

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

 

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Last edited: Nov 27, 2016

Reactions: Boosted92LX

General karthief

wonder how much it would cost to ship you a pair

Mod Dude

Aug 25, 2016

28,117

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polk county florida

Nov 27, 2016

#6

• Nov 27, 2016

• #6

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

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

43,355

18,101

224

Massachusetts

Nov 27, 2016

#7

• Nov 27, 2016

• #7

This may help

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


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mikestang63

SN Certified Technician

Aug 27, 2012

11,606

8,859

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In the garage

Nov 27, 2016

#8

• Nov 27, 2016

• #8

karthief said:

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

Click to expand...

 

Reactions: Davedacarpainter, RaggedGT and General karthief

Sun Dropsz

New Member

Nov 25, 2016

22

2

3

Huntsville, Alabama

Dec 4, 2016

#9

• Dec 4, 2016

• #9

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 is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

43,355

18,101

224

Massachusetts

Dec 5, 2016

#10

• Dec 5, 2016

• #10

That's not it.

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

 

Saleen0679

10 Year Member

Apr 14, 2005

876

24

49

Yakima, WA

Dec 5, 2016

#11

• Dec 5, 2016

• #11

Sun Dropsz said:

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.

Click to expand...

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

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

43,355

18,101

224

Massachusetts

Dec 5, 2016

#12

• Dec 5, 2016

• #12

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.