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Discussion Starter · #1 ·
I've been refurbishing my heater, and in the process managed to screw up my heater fan circuit. I have confirmed that the fan actually works by connecting 12v to it directly through the bullet connectors under the hood. I'm pretty sure the four-position switch on the heater control is working - I've checked resistance to ground from the connector on the heater box. I've replaced the resistor unit in the heater box with a new one. I have continuity between the single connector on the heater box (bottom of the resistor unit) and the bullet connector at the fan. The 14a fuse in the fuse block is good. But, I was expecting to measure 12v at the 14a fuse when I switched to ACC with the key, and it measures zip. The radio is working right, so the ACC switch must be ok - right? What would cause me not to see 12v at the heater fan fuse? This used to work before I refurbished the heater, except it was intermittent. I thought that was caused by a bad resistor unit that had been kludged together by the PO. But now it doesn't work at all. TIA!


67 coupe, I6/200, and a C4
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Randy (Learning as I go)
 
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Sounds like a good troubleshooting job so far. Had a similar problem with brake lights which turned out to be the fuse holder. See if you have continuity across the fuse clips with the fuse in place. My problem was slight rust on the holders. Come back with the fix when you get it working.

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How exactly are you measuring the voltage at the fuse?

I'd suspect the heater switch. It's very easy to trouble shoot. Just plug an ohm meter lead into the top slot (going perpendicular to the other 2) and one at a time, check for continuity to the other 2 "slots". Each slot will only work in a single position of the heater switch (key should be off when testing continuity). Don't know about the '67, but the '66 switches are very easy to dismantle clean and re-assemble. They never wear out ... they just get filled with sludge.

If you always do what you've always done,
You'll always get what you've always got

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I'd suspect the fuse box too, mine's original, and a bit oxidized. have had to do some cleaning, and threw on some spark plug wire silicone for good measure. I know I'll be replacing it.

http://66cherry.stangnet.com
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66 Vert, new 302 roller
99 Expedition Custom
90 Caravan
 

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Discussion Starter · #5 ·
I'm measuring the voltage at the fuse with a DVM lead on the fuse (either end) and a lead on the radio ground point. I can find 12v on other fuses (didn't notice which ones) this way, but not on the heater fan fuse. I have checked the switch as you indicate and it is fine. Pretty sure the problem is either the fuse holder, as others have indicated, or the ignition switch. Guess the next step is to take the fuse holder out and clean it up.


67 coupe, I6/200, and a C4
http://home.att.net/~wr.moore/LeftRear1.jpg
Randy (Learning as I go)
 

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Keep on working at getting 12 V at fuze. wire 21 (yellow) brings 12 V to B terminal of ign switch which goes to A terminal of ign switch and then thru switch and wire 297 (blk with grn stripe i believe) to the fuze top. - until you get this you are wasting your time looking for anything else. it would probably be easiest to get 12 V at B term of ign sw then put in ACC position and see 12 V at A terminal of ign switch. then onlly wire 297 or fuze holder can be problem which is nasty to work on. keep at it and let us know what you found
 
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