86 Mustang Heat Troubleshooting - Help!

rock4451

Dirt-Old 20+Year Member
Nov 30, 2004
12
1
29
New Baden, IL
So I got the 86 started and running! What a relief, such a good feeling to hear it fire up with no leaks, but when I hit the switch for the heat, nothing happened. I do not remember connecting any vacuum lines for the heater, the car has no A/C, and the fan does not blow or turn on when I flip the switch to ON for the heater. I checked fuse 9 in the fuse box (30amp) and it's fine, not blown.

I'm ready for any advice or help, I just installed a 95 motor in an 86 Mustang so surely some heater vacuum routing and wiring shouldn't be awful in comparison. Where do I start?
 
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Visit the site below and download the manual. V8only (Jeremy) who helped you in your last post is the one who will have the answers to many of your questions.
@v8only

See http://slantnosefox.com/picturehosting/jeremy/86 electrical & vacuum troubleshooting manual.zip you can download the whole set of electrical troubleshooting and diagrams for an 86 Mustang courtesy of Jeremy, AKA V8only.
It is a big 61 MB download that you get to unzip and save on your computer. It may take some time to download it, but the results are worth your time.
 
Have you downloaded my manual yet? I'm not at home at the moment access to a computer is difficult...I can work with the wiring diagram as soon as I get a chance, however, the first step is you pulling up the specific diagram and testing for voltage at the back of the motor... if nothing there go back to the switch if you're not getting voltage there, backup and test it coming out of the fuse box. We have to look at the complete picture to trace the pathways of the wiring all the way
 
This diagram is straight out of the manual from above. Use it to help your troubleshooting. FYI, there should be a ground behind the glove box...since you were likely in this general area with your wiring swap, it's very likely that you broke the ground for the circuit.
 

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My CC255 connector is hanging by itself and isn't on the same assembly as my resistors.
Here is my resistor, top left is yellow with red, top right is black, middle wire is orange with black, and bottom wire is light green with white.
Heater_Resistor.jpg

This doesn't reflect the wiring in the diagram you posted, but I'd assume they do the same thing that the wires in that place in the diagram do? I tested the voltage with the key on and a ground and I'm getting power to every resistor coil, which I understand will happen since I used a battery ground and didn't use the switch itself which grounds the appropriate selection. The resistor seems to have voltage throughout, the orange with black wire is getting power on the resistor connector, I'm assuming the black is a ground, and one of the other wires was getting power, too, I forget which one. Are the all orange and all black wires just going to the blower motor? If that's the case, I checked the dark blue with green wire and it's getting power, but the orange with black wire isn't on that connector (CC255 but mine is free and not attached to resistor assembly).

My dark blue with green wire connects to the orange wire on the connector and my orange with black wire connects to the black wire on the connector.

Lastly, this connector was hanging freely with nothing connected to it up by the selector switch wiring on my instrument panel. I don't know if this needs to go to anything.

Open_Connector.jpg
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The resistor bank typically fits in a hole in the blower motor case. The blower air helps keep it from overheating. I hope that is where yours was prior to this photo...

mustang-fan-wiring-gif.86459
 

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Yes that's where it was. I'm just confused as to why diagrams show brown/orange wire and my resistor assembly has yellow with red and light green with white on the bottom terminal. I'm not home now to trace where those wires lead to. Could I put 12v to the orange wire and ground the black wire of my blower motor to make sure it works?
 
Yes that's where it was. I'm just confused as to why diagrams show brown/orange wire and my resistor assembly has yellow with red and light green with white on the bottom terminal. I'm not home now to trace where those wires lead to. Could I put 12v to the orange wire and ground the black wire of my blower motor to make sure it works?
The blower motor should ground through the metal case unless it is mounted in a plastic or fiber duct. In that case, it would need a ground wire.

Other that that, you should be correct in your assumptions. Just be sure to use a jumper with a 30 amp fuse to protect things.
 
When going through those pages in the manual, I found this; which wire colors reflect exactly the colors that go to my resistor assembly pictured in post #6.
HEATERWIRES.jpg
I'm wondering now if there is another resistor assembly I'm missing or what. The one I have in post 6 is right behind my glove box on the black box.

Edit: Also, when testing to make sure my blower motor is getting power, I should check the orange/black and dark blue/light green wires, but do they both get voltage? Will one get voltage depending on what the selector switch is on? Sorry if this is a painfully obviously answered question, I'm just trying to make heads and tails of the wire colors on my resistor and why they're not the same as diagrams say they should be. If I know what to check for on the 2 blower motor wires, I can eliminate the blower as the culprit. I've never torn into a heater before so my knowledge of the layout is basically nonexistent.
 
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