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  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech

No rear defroster, where is the relay???

  • Thread starter Thread starter decableguy2000
  • Start date Start date Nov 7, 2022
D

decableguy2000

Member
Oct 30, 2020
5
1
13
WNC
Nov 7, 2022
#1
  • Nov 7, 2022
  • #1
O3 GT with no rear defroster. I have power at both fuses. Switch has power coming in and when pressed power leaving, but no power coming back from relay to illuminate switch.
 
Last edited: Nov 7, 2022
P

PSKSAM2

Founding Member
Feb 13, 2002
771
8
38
NJ
Nov 8, 2022
#2
  • Nov 8, 2022
  • #2
Did you check "behind center of dash"? Sorry, couldn't resist.

I found mine on my 2002 on the passenger side of the center console, up under the dash. The first pic is looking up at it from the passenger footwell. The connector is clipped onto a small metal tab. Just press the plastic release and it should slide down, then you can take the relay off of the connector. I felt and heard mine audibly click when I put the key in the ignition to ON and pressed the defroster switch. The wire colors also seem to agree with your diagram.
 

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Last edited: Nov 8, 2022
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decableguy2000

Member
Oct 30, 2020
5
1
13
WNC
Nov 9, 2022
#3
  • Nov 9, 2022
  • #3
PSKSAM2 said:
Did you check "behind center of dash"? Sorry, couldn't resist.

I found mine on my 2002 on the passenger side of the center console, up under the dash. The first pic is looking up at it from the passenger footwell. The connector is clipped onto a small metal tab. Just press the plastic release and it should slide down, then you can take the relay off of the connector. I felt and heard mine audibly click when I put the key in the ignition to ON and pressed the defroster switch. The wire colors also seem to agree with your diagram.
Click to expand...

That figures, had the drivers side pulled apart, radio out. All the parts piled in the passenger seat. If it was snake it would have bit me. The wiring diagram should read Center console behind glove box. Popped glove box out last night in the dark and could see it. Will continue with trouble shooting it after work this evening. I owe you a beer.
 
P

PSKSAM2

Founding Member
Feb 13, 2002
771
8
38
NJ
Nov 9, 2022
#4
  • Nov 9, 2022
  • #4
Glad to help! . People on this site have saved me a lot of time and pain over the years.

Seems like your measurements have it down to the culprit, but let us know how it works out! I'm curious how you source a replacement relay, I didn't find that part number available directly.
 
D

decableguy2000

Member
Oct 30, 2020
5
1
13
WNC
Nov 10, 2022
#5
  • Nov 10, 2022
  • #5
I won't mess with until my next day off. As far as a replacement goes, I will snag one off a 2000 parts car we have if its in the same location. While doing some research I found this. Looks like it maybe a standard relay. I will try it out and report back.
 
D

decableguy2000

Member
Oct 30, 2020
5
1
13
WNC
Nov 13, 2022
#6
  • Nov 13, 2022
  • #6
Definitely the relay. It's a standard 5 pin relay in a fancy box to hold it on the chassis. Swapped with horn relay form my 2000, defogger relay is not in the same location and going hunting for it now. Looks like its all part of the switch on the 2000
 
Last edited: Nov 13, 2022
P

PSKSAM2

Founding Member
Feb 13, 2002
771
8
38
NJ
Nov 13, 2022
#7
  • Nov 13, 2022
  • #7
That's good to hear. At least you know what the issue is!
 
S

Shuttleman83

Active Member
Jun 30, 2019
239
13
28
USA
Jan 22, 2023
#8
  • Jan 22, 2023
  • #8
This happened to me. I got a new rear defrost unit / relay and no power even with good fuses and links etc. Needed jump started to get going with some wire.
 
A

apple99Mustangdude

Member
Feb 11, 2018
62
9
18
Oct 14, 2026
#9
  • Oct 14, 2026
  • #9
PSKSAM2 said:
Did you check "behind center of dash"? Sorry, couldn't resist.

I found mine on my 2002 on the passenger side of the center console, up under the dash. The first pic is looking up at it from the passenger footwell. The connector is clipped onto a small metal tab. Just press the plastic release and it should slide down, then you can take the relay off of the connector. I felt and heard mine audibly click when I put the key in the ignition to ON and pressed the defroster switch. The wire colors also seem to agree with your diagram.
Click to expand...
 
A

apple99Mustangdude

Member
Feb 11, 2018
62
9
18
Oct 14, 2026
#10
  • Oct 14, 2026
  • #10
Any info on the 1999 Mustang base model? I saw the relay available on Partsgeek, ordered it, and what I received did not match my car - when I pulled my underhood power box cover, and checked my owners manual, no relay showed for rear window defroster switch, only 3 showed. I was going to pull relay and check to see if any DID control them, but could not get them out. Went back upstairs, put this into a search engine again, and it said that the relay is part of the rear window defroster switch itself? Is this true, and if so do I need to replace the whole switch, or can I replace just the relay? The symptom is that occasionally the rear window defroster will not work, and I have to shut off the engine, re-start, and then it work. Without re-starting the engine, the rear window defroster will not start to work if it didn't work from the git-go, no matter how far I drive and how many times I try.
 
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