72 Swinger Harness Replacement

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Cheddar Greg

Cheddar Greg

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Hi everyone,

I recently purchased a 1972 Swinger and discovered the dash harness burnt up from the ammeter wire to the alternator wire. I purchased an M&H harness through Year One. After removing the original harness and comparing it to the new harness, I noticed some differences which brings me here with some questions.

For the door switches, my original harness has three wires going to the LH switch and two wires going to the RH switch. The new M&H harness has two wires going to LH and only one going to RH.

Would this be a mistake made in the new harness?
The other thing I noticed is the wiring for the map light is different between the harnesses.

I know there are two part # harnesses (early and late production) however I dont know what my car is due to the fender tag being missing. I do have the late production harness. Year One part # HU319A

Any input would be greatly appreciated.

Picture from day of purchase.
 
So, no build sheet either? Whats your door decal show? MDH numbers. I found M&H harnesses to be pretty accurate.
 
crewchief said:
So, no build sheet either? Whats your door decal show? MDH numbers. I found M&H harnesses to be pretty accurate.
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I looked under back seat for build sheet - nothing. Don’t recall seeing a door decal either, I’ll have to take another look. The rest of the harness is very accurate. It was missing a wire from the wiper switch to the motor but I just reused the original.
 
It's too bad no build sheet or tag. Wonder what's the history behind it. Any idea?
 
Didn’t get a whole lot of info on it. I got it from a classic car dealer. I was told the PO put some parts on it to make it look hopped up (ladder bars, hood scoop, etc.) Its a 318 auto. I found the harness chasing what I thought would be burnt out cluster bulbs. I got lucky my new purchase didn’t go up in flames.
 
That's the one thing that always bothers me. I would hate to see mine go up in flames. I think after 46 years of ownership I would just cry like a baby if that ever happened. That's why I have a halon bottle with me.
I replaced my engine compartment wiring due to the fact that it was exposed to engine heat since new. I do like the H&M wiring.
 
crewchief said:
So, no build sheet either? Whats your door decal show? MDH numbers. I found M&H harnesses to be pretty accurate.
Click to expand...
I would agree with crewchief regarding M&H. I would bet somebody in the past put a close (a year or 2 in either direction?) dash harness in the car without fixing the root electrical problem. Factory Service Manual has the wiring diagram to confirm what is correct. Somewhere there is a site with those things posted, but I'm an old school paper book kinda guy, so somebody else will have to point you there...
 
The wiring diagram I have (from Classic Industries) is more accurate with the original harness and not the M&H.

wiring diagram also shows three wires to Lh door switch and two wires to rh

The diagram does not however have any map light wiring shown.

I just don’t want to have to pull the harness back out if there’s a problem

I did recheck for door sticker - nothing there
 
Great Greg

I did see that the harness is date sensitive that's why I asked about the door sticker. Too bad it was gone. Not sure why all valuable ID's were removed. I don't think there's any way to find out that info you need when all you have is a vin. Sometimes build sheets can be found above the glove box.
I don't see why someone would remove it from behind the rear seat back.
 
crewchief said:
Great Greg

I did see that the harness is date sensitive that's why I asked about the door sticker. Too bad it was gone. Not sure why all valuable ID's were removed. I don't think there's any way to find out that info you need when all you have is a vin. Sometimes build sheets can be found above the glove box.
I don't see why someone would remove it from behind the rear seat back.
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i did not check seat back, i checked seat bottom. Will have to check the back. I don't understand either, car looks mostly original, was probably repainted, maybe they were removed then and fender tag not put back idk. Just want to get this harness in so i can move on to other things.
Just got off the phone with Year One.
Exchanging harnesses

Thanks for the help.
 
The back is where they place them between the springs and foam. Year One is very good to work with and they have a lot of history knowledge.
If you do find it back there....BE CAREFUL it's fragile (rusty springs tend to stick to the paper).
 
Waiting for correct harness to ship from YearOne, also going to install headlight harness and alternator bypass from cracked back, and rt engineering ivr while everything is apart.

I don't really know what caused the harness to burn up, so I'm trying to take every precaution I can.

The wires that were burnt were red wire going to + side of ammeter all the way from ammeter post to firewall and Black wire that goes to Alternator. Im thinking maybe there was an overcharging situation prior to me buying the car.
 
This exact problem is common and often has to do with the poor connection in the bulkhead connector. The IVR does not connect to the ammeter. Since I always want a mechanical Oil pressure gauge under the dash, and still want an ammeter for diagnostics, I've taken to running those wires to an aftermarket ammeter paired with my oil pressure gauge, at least then the wires are not in the bundle with everything else if something goes wrong. Then you can rig your factory ammeter in the dash to function as a voltmeter. Between the two you have an excellent finger on the pulse of your electrical system.
 
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