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Discussion Starter #1
hello everyone, when i got my project car it came with the heater not working. i have decided to tackle this project and i have verified that the blower motor does work. i have also checked the fuses and verified that the fuse is good and power is running through it. i have checked the yellow wire that connects to the heater blower resistor and cannot get 12 volts no matter what i do. does this mean my problem is with the heater motor blower switch?
 

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Heater blower resistor? Not sure where that is in the circuit or why it's even there, but the conventional routine is to check every component, before and after with a circuit tester, starting at the battery and working toward the load. At some point, you'll find the culprit. The blower switch is a likely culprit. If it isn't the switch, you're looking at a new motor. The switch is a b*tch to get at unless you've already got the dash torn down, but a whole lot easier than the blower.
 

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The blower motor receives power directly from the fuse block and is "hot" any time the key switch is ON. The fan switch on the dash controls the blower motor's ground. The ground wire from the motor goes to the resistor which is attached to the blower housing with the resistor coils inside the housing so that the air flow will cool the coils. The wires from the fan switch connect to 3 terminals on the opposite end of the coils from the motor ground wire. The switch controls how much of the ground circuit goes through the resistor coils. Low speed goes through both coils. Medium speed goes through 1 coil. High speed goes through no coils- it goes directly to ground. To complete the ground circuit the fan switch itself is grounded through it's metal housing which makes contact with the dash panel.
If you have checked for 12V into the motor you should have 12v coming out of the motor going to the resistor.
I was working on a blower motor recently and I found that I could connect the blower's two wires directly to a battery and the blower would run at full speed but when I connected the wiring through the fan switch the motor would not run. I examined the switch with a magnifying glass and there was a "blob" of solder on the edge of the fiber board where the 3 wires connect. A small metal tab that was part of the switches metal housing was bent over and was touching the blob of solder. Apparently after 50 years corrosion had built up on the tab and the solder and electrical contact was lost. I cleaned the tab and blob with flux and heated the blob with a soldering iron until it melted and flowed onto the tab. I confirmed that electrical contact was made and sure enough the blower started functioning properly with the switch.

http://averagejoerestoration.com/resources/mustang-wiring-and-vacuum-diagrams/1967-mustang-wiring-and-vacuum-diagrams/67heater.jpg
 

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The resistor is at the ground end, and is NOT the power supply. If you have a bad fuse, bad switch, cut wire, etc. you will have no power at the resistor.

Check the heater fuse for 12V. If good, connect the power lead on the blower to 12V, and the ground lead to ground. If it runs, reconnect the power lead, and check for 12V into the heater blower switch. If that's good, check for 12V to the resistor. Many things can go wrong. The whole thing could be perfect, and if the ground wire at the resistor is unplugged, the blower won't work.
 

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Testing any sort of switch is easy enough with a multimeter. Basic continuity checking. If you don't have one there's little excuse. Harbor Freight often has coupons for a free digital one with any purchase. (I got one.) You can work around it with just a test light but with a meter you can pull parts off the car and test them where with a light you have to have the battery connected, the key on, etc.
A jumper wire is crude tool you have to be careful with but you can use a jumper wire to bypass stuff like the resistor pack. If you jump it so and the fan runs...Usually when resistor packs fail, you still have full speed fan, just not the lower speeds. Because full speed is straight through. Diverting the power through resistors is what gives you the lower speeds. Notice there was a "usually" in there though.
You've gotten some good help so far, keep on, you'll find the problem.
 

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If you are NOT getting 12V at the YELLOW wire with the ignition switch in the "ON" position then you have an open circuit in the YELLOW wire somewhere between the blower motor resistor and the blower motor itself (provided you're accurate in saying that the motor is receiving 12V).
 

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Discussion Starter #8
i believe i found the problem, i think and im pretty sure it is the fuse box wiring, when i originally checked for 12 volts i pressed on the fuse terminal and got 12 volts and the fuse was not blown. i decided to check it again today after what you guys said and i pulled the fuse to get a good look at it, i noticed that once of the fuse terminals was really lose and now i cannot get 12 volts from either terminal with the fuse in or out so i believe the wiring behind the fuse was on its last leg.
 

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Discussion Starter #9
okay so after checking the wires i confirmed that the problem was the fuse box wiring being rusted. i ordered a fuse repair kit and was on back order which is why it took so long to get back to this thread. now after repairing the fuse box. it seems that the controls by the driver side door are also causing a problem. the controls don't always work, i have to move the switch from one side to another a couple times and then it will turn on and blow.
 

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okay so after checking the wires i confirmed that the problem was the fuse box wiring being rusted. i ordered a fuse repair kit and was on back order which is why it took so long to get back to this thread. now after repairing the fuse box. it seems that the controls by the driver side door are also causing a problem. the controls don't always work, i have to move the switch from one side to another a couple times and then it will turn on and blow.
Scott Drake Store - 1967 Mustang Heater Switch Assembly

On edit - try bartl's 'fix' first. Also make sure the switch is well grounded to the chassis as the switch completes the ground circuit.
Paul
 

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Discussion Starter #12
@ bartl ill try that first.
@Paul1958 everything is grounded properly its just the switch that isnt working properly, ill go buy some electric cleaner and see if that fixes it if not ill order a new switch. ill keep you guys updated on what is happening.
 

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@ bartl ill try that first.
@Paul1958 everything is grounded properly its just the switch that isnt working properly, ill go buy some electric cleaner and see if that fixes it if not ill order a new switch. ill keep you guys updated on what is happening.
I've also been known to pry open slide switches, clean them up, polish the contacts and put them back together. Yes, I'm CHEAP! :pirate:
 

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Discussion Starter #15
good news i got the switch to work, the dielectric grease that was in their from the factory kinda turned into tar and just wouldn't allow the copper pieces to contact fully which caused the inconsistency of the switch. so i brushed it off with a small wire brush and got all the stuff off then put fresh dielectric grease back on and now the switch works like new. thank you @bartl and @Paul1958
 
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