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Discussion Starter · #1 ·
So, my heater core was shot, swapped in a new one and all is well. However, the fan does not have a high speed, just low and medium. The top position of the switch yields no speed increase. Nearly every electrical function in this car has proven to be very clean as far as "crust" and age go, leading me to suspect the heater resistor instead of the switch.

Any quick test to tell? Where is the resistor located? If it is bad, where do I find a replacement?
 

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Discussion Starter · #5 ·
Ah, so 2 votes for switch? FE, you sound a little unsure on the wiring? The switch has 4 positions. The first (other than off) turns the fan barely on, almost can't even tell it's running other than a very quiet hum (only audible with the car off) and some air movement out the vents. The next position up the fan picks up speed, but in the highest position it remains the same as the prior.

I only see one orange and black wire heading through the firewall under the dash. The wiring manual shows a blue and red wire for low and middle speeds, and a black one for a straight ground bypassing the resistor. I wonder if the back direct ground wire is bad/missing.

Where is that resistor located?
 

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So, my heater core was shot, swapped in a new one and all is well. However, the fan does not have a high speed, just low and medium. The top position of the switch yields no speed increase. Nearly every electrical function in this car has proven to be very clean as far as "crust" and age go, leading me to suspect the heater resistor instead of the switch.

Any quick test to tell? Where is the resistor located? If it is bad, where do I find a replacement?

Mine does the same thing. High got intermittent, then quit altogether. So whoever knows the answer gets a 2-fer.
 

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Discussion Starter · #8 ·
Well, it's not the switch. Rather, I should say not the switch alone. I bypassed the switch and grounded the black wire and the fan still did not run at full speed. The wires look immaculate like everything else under the dash and are still solidly loomed from the switch to the top of the heater box.

The other speeds work the same manually grounded as they do through the switch. It appears something is not connecting the black wire through to the fan. Looks like I'm going to have to drop the heater box (AGAIN) to get to the bottom of this.
 

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Discussion Starter · #9 ·
Ka-CHOW! So, it seems the multi spade rubber connectors are a bit finicky and can be difficult to get lined up perfectly on all the contacts. I noticed it was a real pain to get the switch plug back on so I felt up on top of the box where the plug goes in. I could tell the lugs weren't all fully engaged so I wiggled and pushed and suddenly high speed works.

I'm not convinced I have it on all the way yet, but I'm confident if I get back under there with a little mirror I should be able to get it right without dropping the whole box.

Whew!
 

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Probably confused on the windings.... My switch is an Off-Low-High operation. There are no resistors, I was confusing your 63 for a Falcon system not a Fairlane... My bad.

My motor has 2 power wires to the heater motor, the motor get's grounded from a ground coming out of motor to the firewall....

Glad you found your problem :)
 

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Discussion Starter · #11 ·
No problem, easy mistake. Yes I'm glad I found it too, hopefully others might benefit from this thread. Once I figured out the switching/wiring it made sense to pull the plug off the switch and check each terminal. That was how I realized it must be somewhere between the switch, and the orange and black wires. Other than a break in the wire, it could only be the connection at the resistor.

Thanks for the suggestions.
 

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No need for the mirror,....here's the plug in. It's the resistor. Underneath the red fiberglass are two open coils one with twice as many turns as the other.

I just refurbished my entire plenum the other day.

 

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So it is a loose/corroded plug into the terminals on the back of the switch?
Or unscrew the red panel and replace (or refurbish?) the coils inside there? Part number?
 

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Discussion Starter · #15 ·
Hodad, that doesn't look at all like my heater box, might that be a different year? I can feel mine, just can't see it direct line of sight, hence the need for a mirror. Whoa, that could sure be taken differently huh?

Puttster, in my case it was just the plug on the red fiberglass panel that wasn't pushed on completely. My switch was fine, as is the resistor. You can test the contacts of the switch without removing it from the dash. Put one leg of an ohm meter on the ground lug, and check each switch position for a short to it. It is a typical crawl under the dash on your back thing, but you would have to do that to remove it.

If it is determined that the resistor is bad, they can be found on Ebay for a reasonable cost. Just search for heater resistor with model and year.
 

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Discussion Starter · #19 ·
Yes, that's correct. Red blue and black wires through the resistor, as well as straight ground are provided via the switch. In case anyone didn't realize, that's been covered earlier in the thread, and my particular case was resolved.

Thanks everyone for the input. What a great forum, with so many eager to help!

Seems like we should have a sticky of common problems. Seems like heaters, dash bezels, ignition switches etc come up a lot. It would be cool to have an instructional sticky, with only "how to's" based on year and subject.
 

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A few other places have a Sub-forum titled "Tech" in which nothing goes but solutions to common problems. No "Hey guess what I did today?" or "Show us your cool license plate" threads.
 
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