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Discussion Starter · #1 ·
I’ve read numerous posts regarding electric issues Dodge trucks have. My ’74 seems to have some of these problems. What I need advice on is how to approach their repair. My priorities here are based on, most potential “dangerous” first, best repair, ease of repair, my need for the item not working, and improvements/upgrades to be done.

As this is my daily driver I can’t take the truck down for longer than about one day. So believe I will have to address the problems one at a time. The problems are:

- Lights – brake, instrument and interior lights do not work. Headlights etc. dim at idle. Obviously the brake lights area priority. Would replacing the switch be a good start here? I’ve read about a procedure involving installing a relay. Necessary or?

- Heater (w/ A/C) – heater does not blow, A/C most electric connections disconnected under the hood. Heater will be needed soon. Heater fuse mount seems to have been subjected to a load of heat. One side of the fuse mount has melted away. Again, I’ve read about a procedure involving installing a relay. Necessary or? The a/c is not much of a priority for me, but it would be nice to have eventually.

- Ammeter – it works but I’ve read some posts indicating this is a problem spot. Is the bypass procedure a prerequisite to fixing the other items?

- I intend to add additional lights, dual battery system and this may become my race car hauler next season.

- Tachometer – where can I easily attach the power line?

Am I missing anything?

TIA, L
 

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Check the bulbs in the brake lights first, and make sure the housing is making good contact to the bed, as that is how they ground. If all that's good, replace the brake switch, It's a piece of cake to change.

For the tach, I found a few red wires under the dash, to the left of the column that have power when the key is on, I ran mine from there.

Heater blower motors pull a lot of power when running full tilt, probably why the fuse block is melted around it. A relay is not totally necessary but wouldn't be a bad idea.

I've never had any problems w/ my ammeters, but many have. I would say if you are going to run a lot of electrical stuff on the truck, then bypass it.
 

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N=R* Fp Ne Fl Fj Fc L :
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If you are going to get down and dirty I would start with a factory service manual and or the wiring diagrams that match your truck. It will make work a lot easier.

I would also start with the ammeter; no need to get half way through fixing your truck just to see it go up in smoke. Next I would take a meter or a trouble light to your fuse box and start seeing where you have power and where you don't. As many things as you have listed would lead me to believe that you have main power issues; not individual.

Good luck; post up if you need help.
 

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I’ve read numerous posts regarding electric issues Dodge trucks have. My ’74 seems to have some of these problems. What I need advice on is how to approach their repair. My priorities here are based on, most potential “dangerous” first, best repair, ease of repair, my need for the item not working, and improvements/upgrades to be done.
Start reading here...trust me.:) http://www.madelectrical.com/electrical-tech.shtml

As this is my daily driver I can’t take the truck down for longer than about one day. So believe I will have to address the problems one at a time. The problems are:

- Lights – brake, instrument and interior lights do not work. Headlights etc. dim at idle. Obviously the brake lights area priority. Would replacing the switch be a good start here? I’ve read about a procedure involving installing a relay. Necessary or?
If your brake lights do not work check the fuse first, then you should have power going into the brake light switch on the pedal and going out when you step on the pedal. The power goes from there to the turn signal switch, make sure the hazard flashers switch is in or out all the way as this can cause the brake lights to malfunction. The turn signal switch may also be bad.

Replace the headlight switch and the floor mounted dimmer switch. Do NOT use Autozone electrical parts! Get the top of the line NAPA Echlin switches or from an online Mopar dealer that offers a discount. If you need help with part numbers, let me know. You must check the electrical connections at both of these switches for heat damage. If the wiring terminals are NOT bright colored brass looking then they have suffered heat stroke and must be replaced. Install the headlight relays for sure. Pull all of the fuses out of your fuse block and trash them, clean the clips that hold the fuses with a small wire,brass, etc brush(disconnect the battery before doing this). Apply a small film of dielectric grease(from auto parts store) to the clips and snap in brand NEW fuses.

- Heater (w/ A/C) – heater does not blow, A/C most electric connections disconnected under the hood. Heater will be needed soon. Heater fuse mount seems to have been subjected to a load of heat. One side of the fuse mount has melted away. Again, I’ve read about a procedure involving installing a relay. Necessary or? The a/c is not much of a priority for me, but it would be nice to have eventually.
Another nightmare. You will have to check the blower switch on the dash for heat stroke(commonly called thermal runaway), the wiring harness that attaches to it, the other end of the harness that attaches to the blower motor resistor on top of the heater box. Also check the resistor block for damage. From the resistor block power goes to the blower motor and it's wiring. The 20 amp circuit for the blower always melts the fuse block. I have fixed a number of these with a careful clean up of the plastic and using epoxy to secure the fuse clip. Relays in the fan system are a great idea to keep the current out of the dash switch. If you need the blower wiring harness fixed, I can duplicate it for the price of postage back to you.:) It unplugs from the fuse block, switch and resistor block. Dodge didnt start using relays in the truck until the mid 90's!
- Ammeter – it works but I’ve read some posts indicating this is a problem spot. Is the bypass procedure a prerequisite to fixing the other items?
This is a fire hazard, check here for a real good fix.
http://www.madelectrical.com/electricaltech/amp-gauges.shtml


- I intend to add additional lights, dual battery system and this may become my race car hauler next season.
Get a second battery installed with a proper wiring harness and isolator. Hook up all new lights to the second battery using relays. Don't tap into the stock electrical system for high amp add ons. It will only cause more heat stroke!

Am I missing anything?
Yes, but ammeter/brake lights first. :gr_patrio

P.S. I can help you out with the electrical stuff..terminals, wire harnesses etc. I like to repair the harnesses for the challenge. Oh yea...don't use cheap parts. :) Keep in touch.
 

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Discussion Starter · #5 ·
Good stuff guys.

Thanks,
 

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Discussion Starter · #6 ·
Dodge wiring

Start reading here...trust me.:) http://www.madelectrical.com/electrical-tech.shtml

XLNT site - thanks. Gonna do the ammeter ASAP. Do I need to pull the dash panel to bypass the ammeter?


If your brake lights do not work check the fuse first, then you should have power going into the brake light switch on the pedal and going out when you step on the pedal. The power goes from there to the turn signal switch, make sure the hazard flashers switch is in or out all the way as this can cause the brake lights to malfunction. The turn signal switch may also be bad.

Fuse is good - not sure about the fuse block though. No s#)t through the turn sig switch? My t/s switch semi-works, it operates the lights but it won't cancel by it self.

Replace the headlight switch and the floor mounted dimmer switch. Do NOT use Autozone electrical parts!


Yeah AutoZone - BTDT. This makes sense too - headlights go dim at idle.


You will have to check the blower switch on the dash for heat stroke(commonly called thermal runaway), the wiring harness that attaches to it, the other end of the harness that attaches to the blower motor resistor on top of the heater box. Also check the resistor block for damage. From the resistor block power goes to the blower motor and it's wiring. The 20 amp circuit for the blower always melts the fuse block. I have fixed a number of these with a careful clean up of the plastic and using epoxy to secure the fuse clip. Relays in the fan system are a great idea to keep the current out of the dash switch. If you need the blower wiring harness fixed, I can duplicate it for the price of postage back to you.:) It unplugs from the fuse block, switch and resistor block. Dodge didnt start using relays in the truck until the mid 90's!

I'll get in there ASAP and let you know.

Thanks,
 

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Discussion Starter · #7 ·
Chump said:
- Lights – brake, instrument and interior lights do not work. Headlights etc. dim at idle. Obviously the brake lights area priority. Would replacing the switch be a good start here? I’ve read about a procedure involving installing a relay. Necessary or?
If your brake lights do not work check the fuse first, then you should have power going into the brake light switch on the pedal and going out when you step on the pedal. The power goes from there to the turn signal switch, make sure the hazard flashers switch is in or out all the way as this can cause the brake lights to malfunction. The turn signal switch may also be bad.


Fuse is good. Is brake switch a key-on or key-off for power?

Thanks,
 

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Brake switch by itself is normally closed, but is held open by the brake pedal. When you press the brake, it releases the switch and allows it to close, sending power to the brake lights.

I have a '74 with power issues too ... the entire harness burned up at the firewall!!! The engine side of the harness survived, I pulled a very nice dash harness from a '78 ... starter wires are different but everything else matches fine.

Boy am I glad I stumbled on this thread! I'm almost done rewiring but I'll definitely relay the ammeter and headlights before calling it done.

tim
 

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Took a look at the site mentioned, while the the ammeter mod is practical it does not address the fact that you now have a useless gauge sitting in your dash. Has anybody done something different? Is there a Dodge voltmeter gauge that would work in it's place?

Thanks

Ron
 

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Hi all,

I finished rewiring the goat, and bypassed the ammeter as well. She is back on the road!!

But now I dont have ANY working guages. Does the ammeter bypass normally kill all the guages, or does the instrument panel need some power? Perhaps to the ammeter lug(s)? No dash illumination either, the only thing that works are the turn signal indicators and the speedo (after 5 miles). Would a bad regulator cause this, if so how can I test it?

Thanks! tim
 

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"But now I dont have ANY working guages. Does the ammeter bypass normally kill all the guages, or does the instrument panel need some power? Perhaps to the ammeter lug(s)? No dash illumination either, the only thing that works are the turn signal indicators and the speedo (after 5 miles). Would a bad regulator cause this, if so how can I test it?"

My first guess would be that you knocked something loose while you were moving stuff around. You might try wiggling some of the wire bundles around while you're looking at the dash lights. Check for loose connectors, etc.

I'm doing the same kind of thing, (I've got the mother of all wiring issues) I've traced the wire from the blower to some kind of thing that's mounted on the steering column. It also has the ignition switch wires attached to it. What is that? Some sort of resistor?
 

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Howard78 said:
"But now I dont have ANY working guages. Does the ammeter bypass normally kill all the guages, or does the instrument panel need some power? Perhaps to the ammeter lug(s)? No dash illumination either, the only thing that works are the turn signal indicators and the speedo (after 5 miles). Would a bad regulator cause this, if so how can I test it?"

My first guess would be that you knocked something loose while you were moving stuff around. You might try wiggling some of the wire bundles around while you're looking at the dash lights. Check for loose connectors, etc.

I'm doing the same kind of thing, (I've got the mother of all wiring issues) I've traced the wire from the blower to some kind of thing that's mounted on the steering column. It also has the ignition switch wires attached to it. What is that? Some sort of resistor?
HOWARD78...do you have a tilt steering column?
 

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timethy said:
Hi all,

I finished rewiring the goat, and bypassed the ammeter as well. She is back on the road!!

But now I dont have ANY working guages. Does the ammeter bypass normally kill all the guages, or does the instrument panel need some power? Perhaps to the ammeter lug(s)? No dash illumination either, the only thing that works are the turn signal indicators and the speedo (after 5 miles). Would a bad regulator cause this, if so how can I test it?

Thanks! tim
There's at least 4 different wiring harnesses from 74-78...they just don't plug and play. There are subtle differences. Does the wiring on the round gray connector match this 74 wiring diagram?
 

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Chump, yes it has a tilt wheel. Also has cruise control on the turn signal stalk, but I haven't seen any evidence of other related cruise control parts anywhere. Except maybe this little ribbon cable thats dangling down from the steering column not attached to anything.

How do you get at the ignition switch? Do you have to take the steering wheel off? I've got a puller, so that wouldn't be a problem I'd really like to verify whats going to the switch. I only have the Haynes manual, which says something like Typical 1978 and Earlier wiring, etc. They show a pink wire going to the coil in the start position. But mine doesn't have any pink wire anywhere. Its orange. And it goes to a different fire wall connector than what they show. Let me back up, I'm getting confused.

That curved connector thing has these wires, from one side to the other: Bl, Or, Bl, Rd, Bk, Bl, Bk. One of the Blues comes from the heater fuse. The side that connects to the steering column terminates in two square connectors, and those are plugged into some big green connector thing. Do some wires come out the back of that, and go up the column? To the switch?

I think some previous owner/dumbass may have switched a couple of these wires around at the firewall. The pink and orange from the ignition switch. And I hooked it back up the way they had it, and now I've got the overcharging/exploding battery problem. As well as the heater problem, and the gauge problem. Hell I just got all kinds of problems.

I wouldn't be surprised if they switched the whole harness from some other truck. I'll have to try and take a picture of the bypassed heater switch conglomeration, and post it for informational purposes. But anyway, I've got everything untaped, and am becoming more familiar with it. I'll keep ya posted.
 

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If it's a tilt column then the ignition switch is right where you found it..at the bottom of the column. The column is made by Saginaw(GM) and uses a GM style switch like below. You will find a short harness that adapts the gray half moon connector to the 2 square plugs on the ignition switch. These 2 plugs like to melt and so does the switch.

 

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Howard78 said:
Here we go. What's wrong with this picture?
Must have been too lazy to mount the switch in the control or he got the wrong switch and he didnt know that he can get a repair connector for that or he didnt know that I would fix his harness for the cost of postage! Moron at large!!!! :crazy:
 

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Alright, I've had about enough from you Mr Wiggly Ears. I'm gonna be looking for you cruising around the local Burger King And when I find ya, look out!
 

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Hey, just kidding Brucey-Baby. I wouldn't want to hurt your feelings.

I went to the junkyard today, and the instrument cluster from the '78 was gone. Wouldn't ya know. If I'd a had an extra $20 the last time I went there...Oh well. They got a old red, long-bed crew cab '78. It's got pretty good fenders. They also had a '85 or '86 Ramcharger that had some very nice sheetmetal on it. Almost new looking. I'm thinking about getting the inner fender well off of that one. Mines all crapped out from battery acid. I went there about 3 weeks ago and took the battery tray off the Ramcharger. Problem is, they don't keep stuff there for long. They're always gleefully crushing cars at an alarming pace everytime I go there. Or if you see something you want, and you come back a day later, its gone.

I'm still working on the wiring problems. Got my first paycheck. Paid some bills and then went out and blew the rest on parts. I'm hoping to get this thing on the road soon. Wish me luck!
 
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