1989 Mustang Defroster Help Needed

[TechSteele]

Hello People,

Got a Problem, I have Several, but this is the Latest.

I am currently trying to put the Electrical systems in this car back the way it should be (1989 Mustang 5.0 Hatchback). It is tore to heck from previous owners

The Rear Window Defroster wiring is driving me Nuts.

If anyone has wiring diagrams for the body wiring it would really help.

I Can Not Find the rear defroster Relay, anyone know where it SHOULD be mounted? I would think it would be on the drivers side of the dash, but for the life of me, i can not find it. I Really do not want to take off the dash, if its not needed.
The wires from the switch go into the darkness, and from the fuse box, itsd Really hard to track from there.

Second thing, Anyone know the wire colors of the ones going To the rear defroster from the front to the connector in the back?

Found the connector in the back end that goes to the window, but can not find which wire it should hook into to go forward, or bring the signal to the back.

There are a few other connectors that dont seem to have a mate, but if someone has a diagram, i may be able to figure it out. They may not even be needed for anything important.

Thanks for any help you may be able to give me,

Steele

 

[jrichker]

Send me your email address and I will send you a complete wiring diagram set for an 89 Mustang. It is too big to fit through Stangnet's email gateway or messaging system.

 

[TechSteele]

Recieved it,
Thanks.
Its Like the Haynes ones, but, on the computer i can Zoom in and actually Read them, hehe

Would still Like to know where the Rear Defroster Relay is Located if anyone can help with that part.

Or if anyone knows colors off the top of there head.

I will go over these again, now that a can read them without a magnifying glass hehe

 

[TechSteele]

Still trying

Welp, It helped, a Little.

I Think i found where the relay SHOULD have been.
Its a square 4 pin plug, which is different then the relay i have from a 91 mustang, which has a flat/rectangle 5 pin connector. The Colors are real close, only one different.

I still, can not find any wire going from the front to the back.

There is a Black w/ a Yellow stripe wire up front that goes to a single pin plug in the dash, from what i believe to be the relay plug, but, it goes nowhere, plus there is a twin taped to it, right next to it, that SEEMS, to go to the engine compartment.

It would be Number 175 on the diagram, located at 47-48 A on the schematics.

If you go to 86 F, it shows a Grey w/ Yellow Stripe, 687 12ga, BUT, if you look at 48 A, its not there, and the Blk/Y one is on a different pin

The wire going to the rear defroster grid, IS Grey w/ Yellow Stripe, and goes to a plug in the back, but no mate anywhere to be found.

Its driving me NUTS

 

[Saleen0679]

The Defrost Control Relay is immediately to the right of the fuse box and behind the trim panel. It is mounted upside down onto the metal brace.

There are six wires connected:

GY/LB
P/O x 2
BK/Y
BK
BR/LB

 

[TechSteele]

I Just looked, and (of course) Nothing there.
This the weirdest car i have EVER seen.
Its like some people played a game of lets change or rip something out, and see if you can fix or find it, and NO ONE, ever won a round, but continued to play for months

 

[TechSteele]

dia pic

This may help some

 

[Saleen0679]

The connector marked 'No Idea' is the connector for the Defrost Relay. The 'Empty plug' must be the connector used when the convertible top switch is used.

 

[TechSteele]

For Others

For Others Fighting this problem,
I ran accross this Web Page
Untitled Document

It helped a Little. I at Least Found the Plug where the Relay SHOULD have been.
It was stuffed up in there real good, but found it.

I STILL cant figure out what wire is to go to the back end.
I THINK, its that Black and Yellow one, which i would need to add to and run it back.

Now i just need a E7ZB-18C641-AA Relay

 

[TechSteele]

More for Others

Pic of the Dang Blasted Relay I am Missing.


Edit*
I did get this working with a Relay i had from a 91' mustang.

Only took 3 trips to the Auto Parts Store, and one to the nearest Ford Dealer, and about 5 hours of work

The wires were the same on the 91' relay, the relay was just a little different.
It didnt plug right in, the plugs were different.
I Had to run wires from the pins on the newer relay (spade connectors F), to the plug slots (spade Connectors M), but it worked.

Also, I found out with a MultiMeter, the "Found Plug" above may be used for a Convertable as well, BUT, its also used for the rear defroster.

I ran a wire from the 4 Pin Plug, from the Brown/LtBlue Stripe wire Pin, to the back and connected it to the Grey/Yellow Stripe wire that goes to the Positive side of the Heater Grid.

The Br/LtB wire is only energized when the relay timer is running.

Thought i would finish this little story for you incase someone else needs it.

 

[TechSteele]

Added Pic of Wiring Diagram

 

[Saleen0679]

There is a Black w/ a Yellow stripe wire up front that goes to a single pin plug in the dash, from what i believe to be the relay plug, but, it goes nowhere, plus there is a twin taped to it, right next to it, that SEEMS, to go to the engine compartment.

It would be Number 175 on the diagram, located at 47-48 A on the schematics.

If you go to 86 F, it shows a Grey w/ Yellow Stripe, 687 12ga, BUT, if you look at 48 A, its not there, and the Blk/Y one is on a different pin

I missed it during my first read, but the two small connectors up in the dash with the BK/Y wires are for the convertible top circuit breaker. They just hang there on other models.

The wires were the same on the 91' relay, the relay was just a little different. It didnt plug right in, the plugs were different.
I Had to run wires from the pins on the newer relay (spade connectors F), to the plug slots (spade Connectors M), but it worked.

I think Ford changed the relay in '90 going from the squarish to the rectangular plug which adds to another inconsistency throughout the 87-93 model years. I'm not sure the relays are even available anymore. I've grabbed and tested spare relays from the junkyard.

Also, I found out with a MultiMeter, the "Found Plug" above may be used for a Convertable as well, BUT, its also used for the rear defroster..

If the 'Found Plug' is located in the LH trim panel then it would be for the defroster. It is C281 (a gray four-pin) in the diagram. I was assuming all the connectors you found were under the dash.

 

[TechSteele]

The Grey 4 pin plug was comming out of the main bundle, on the left side, and was originally under the kick panel, if i remember right.

The 5 pin where the defroster relay SHould be, was tucked up under the dash, near the steering colum, sort of behind the dimmer switch.

A circut breaker going to those Blk/Y wires would make sence. The one going to the Engine compartment says it is fuse linked at the starter, i do know its energized with the key on, i tested it first.
It may be a good power take off with an inline fuse if needed in the future. (not sure)

I really didnt know all the differences between the different Foxes untill i started working on this thing. ( a sticky list would be nice if someone was able to compile one)
The first problem i had was no wipers. Got a 91' Multi switch, no go, only the blinkers worked. THEN, i read about the internal wiring being different. Got an 89' one, and everything was fine.
The Dash Gauge bezel is 87-89 as well.
The Dinger/Horn and Day/Night relays were all the same as the 91', i replaced them in my 89'.
( I had bought a whole box of electrical parts from a 91' a while back, thinking i would have spares, some are)

Auto Zone couldnt find a relay even close, and nothing with that part number in their system, Ford, said discontinued a long time ago, so if anyone needs one of these relays, its Junk Yard only. I didnt ask about the newer relays.

I signed up for a Year of AllDataDIY, it isnt perfect, but their diagrams helped in 2 places already.

 

[Saleen0679]

You should invest in a 1989 Mustang EVTM. The electrical/vacuum manuals are specific to each vehicle.