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1979 Bronco 400ci Holley 4 BBL C6
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Discussion Starter #1 (Edited)
So I've spent the last few months getting all the wiring sorted out on the 79. I have a few plugs/wired that I haven't been able to identify on any of the diagrams I got from around here, or other sources(Probably helps that I'm colorblind as sin, yay me). This is a truck that hasn't been started in about 8 or so years, and was on the middle of being converted to an ATO fuse panel, and throttle body injection. I'm trying to bring as much as I can back to stock electrically to before I focus on the engine. So far, everything seems to work exept:
1. Rear window. Pretty sure it's the motor. Get power to the connector going into the tailgate from the dash. Haven't been inside to go deeper yet.
2. Dash lights seem very dim. They are lit up, but they are very faint
Adjusting the dimmer makes them even more dim, but not brighter.
3. Fuel gauge peggs. Pretty sure I have a short, cutting into those wires next.
So as far as the mystery wires..
168856

Second one right behind that...
168858

This is a wire that I wasn't sure, but thought it needed to go to solenoid from what I was able to put together from the schematics. It's the black with white or green stripe. The one spliced to the red.
168859

Headed under the dash now... The yellow sob. No idea.
168860

Likewise on this...
168861

That one is the single wire connector. Any thoughts or ideas on what I'm looking at would be much appreciated. Thanks guys.
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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First pic does not look factory.

The black with white or green stripe, the stripe is white. Idk where it goes though.

Yellow SOB under dash doesnt look factory either.
 

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1979 Bronco 400ci Holley 4 BBL C6
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Discussion Starter #4
Interesting that you don't think it's factory stuff. I always had a feeling the PO had done some fun things electrically with this.

First picture plug gets voltage key on to one terminal. There used to be dual battery's, don't remember what was in there as far as a relay/battery isolator. All other Connectors seem dead. I guess Ill go back to the drawing board/test light...

Thanks again guys,
Peter
 

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I have some answers not guesses
I have repaired/reWired several harnesses on these rigs
I do not recall each and every wire but here is what I know

First picture red plug not sure

Other plug is window washer pump motor

Second picture
2 wire plug with black and white wire is for the reverse lights on a manual transmission. Put a jumper in that plug and see the lights come on
As with many optional parts the wire harness is equipped for either an auto or a standard. You may find various plugs hanging empty from ford as a result . A manual rig will have a harness for automatic tranny reverse lights etc. this helps us out when we swap out parts or add optional lights accessories :)

black wire white stripe with red splice
This is for the rear glass. It is suppose to have a circuit breaker in it that auto resets when it cools

under dash
Yellow plug is a convince wire.
each hole is 12 volt keyed ignition
Used to add Accessories that only come one with key. Example. Radio

off topic but if you go to the glove box area you will find another plug like it that is constant 12 v. Same circuit the dome lights are on as is the glove box door light if equipped
If it’s not equipped with glove box light that plug will be hanging empty just like your manual trans reverse light plug is empty. If it has a glove box light that is where the light plugs in under dash



last one i THINK is part of the heating cooling AC circuit.
I will check and see if I can verify that and post back

As for dash lights they never were too bright. But you may have a bad re o stat. It’s easily changed as it’s part of the Headlight switch in the cab

all is factory that you have pictured
 

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The last one is for the blower motor heat AC
Is your bronco ac or heat only from factory?
I ask because on a factory ac that plug is under the hood Where it plugs in
It may belong in the cab on a non AC rig. That I do not re call
Get a meter out and check it for power with the fan on
 

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169057

it’s hard to photo that is the circuit breaker on the black white stripe wire for rear window motor
Looks like someone removed it trying to fix the rear window or it went bad and just tossed it out
Get another so you do not have to worry about melting wires or a fire if for some reason the motor were to get stuck on
The one pictures is original 78. I don’t think they fail often
It is there for that period of time you hold the window switch to close window when it’s already closed. Lol
Have any kids?
 

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Oh. Just came to me. the red plug under hood driver side is for cruise control.
Your rig looks loaded. I see the under dash lighting.
 

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1979 Bronco 400ci Holley 4 BBL C6
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Discussion Starter #13
Right on man, thanks for all that.

Yes, it was originally equiped with factory ac, as well as cruise. I'll take a better look at it tonite with all of that in mind. Thanks again.

Oh, and I definitely want to go back to a duel battery setup. I think I'm going to do that when I upgrade the alternator/charging system. Just curious tho, pressure switch?
 

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Oil pressure switch to drop auxiliary battery into circuit only when there is oil pressure. (Engine running)
This way aux battery is isolated from main battery and the bronco when engine is off
Can not drain aux battery dead When parked
If main battery dies from Lights left on or radio
Push button in cab that engages aux battery to start Emgune
self rescue without opening the hood
Go one wire ALT when you upgrade
Get rid of the regulator and wire mess
 

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169069


if the main battery goes dead and bronco won’t turn over I can push and hold in the top button. It engages the aux battery to become in parallel lell with the main battery as I have no oil pressure
Push start button After engine starts the oil pressure switch keeps the batteries in series charging them both until engine shuts off
 

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1979 Bronco 400ci Holley 4 BBL C6
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Discussion Starter #16
Would setting it up that way have any advantages compared to a traditional 3 post battery isolator?

Was either going to do the 3g alternator conversion, or go with a gm 1 wire. Leaning towards the latter for simplicity/availability.

What amp circuit breaker should be online for the black/white stripe wire?
 

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Oh. If you are wondering why the starter button
It’s because I got rid of the resister wire from ignition key to coil. You know the one that melts after years causing us problems with Getting good volts to the coil
there might be a better way but this works good for me. It’s just turn the key to run position. Push button to crank
 

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Not familiar with the 3 post
But I think self rescue might be only diff

30 amp breaker should be fine

I went with the one wire ALT from JBG
I think it is indeed GM
Been trouble free for 12 years
 

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Some just run the batteries in parallel at all times for double the capacity
Always in parallel. I think I been saying series. That’s incorrect. Series would make 24 volts. No good.
I had my wires crossed so to speak lol

Have a link to the three post? Curious now

I think I steered you wrong on that picture I said window washer. Not sure what that one is.
Going to say cruise. My rigs do not have that plug anymore. I got rid of the cruise so might be that’s where it went
 
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