Gauge lights wont turn on 74 Dart Sport

[BornNaked]

Hey fellas,

I have been getting my 74 Dart Sport ready to be back on the road after 20 years of sitting.

Im having a few electrical problems that I need some guidance on. The cluster lights dont turn on at all when you turn the dial. However, my headlights do turn on when you pull the dial. I initially thought it was the switch, I pulled it and did see some rusty build up. I cleaned both ends with electrical cleaner (pictured below) but to no luck after I tested. I just bought a new headlamp switch off classic industry hoping this is my fail point.

My second electrical problem is that when I have my headlights on, and step on the high beam switch on the floor, my headlights go out. The running lights stay on, headlamps go dark. I did replace the switch but I get the same results.

Im no electrician and fairly new to this hobby, any tips are appreciated.

]Are these issues related? Any ideas for me to troubleshoot?


Thanks in advanced!

 

[67Dart273]

The headlights/ and floor dimmer circuit is simple. The headlight switch merely feeds headlights power to the dimmer which is a spdt (single pole double throw) switch. So with the light switch on, and no matter which way the dimmer is "switched," there should be TWO of the 3 terminals hot. And when you switch the dimmer, the one that is dead should come hot, and one of the other two should go dead. The two that switch, send hi or lo beam power out through the bulkhead terminals on two different wires.

Of that seems to be OK at the switch, you may have a bad connection where one of the two wires feeds through the bulkhead connector, or it may be a wiring problem out at the headlights end. IT IS NOT unheard of for both lamps to have one filament burned out. If you have power at both terminals of the switch, go out into the engine bay and probe the bulkhead connector. If you have power there for both hi and low, move on out to one or the other headlamps and check that out

Cluster lamps. "Work" the dimmer control back and forth vigorously. Now get down into the fuse panel and find the "inst" fuse which is normally at one end of the box. If you look at the rear of the fuse box, one end of that fuse will have a tan, and the other end will have several organge wires. The tan comes from the dimmer control, and the orange are all the dimmer controlled feeds to various lamps

DO THE park and tail lamps work? There are TWO hot feeds to the light switch. One is UNfused, ONLY for the headlights, which has a breaker in the switch. That is B1 at the switch

B2 is fed from a fuse, and powers tail, park, and the cluster lamps. The dimmer taps power off of that in the switch, through the dimmer, out on tan, and down through the inst fuse in the fuse panel. From there out to all the oraange.

So the tail fuse has to be good, the tail / park circuit has to work, the dimmer control must be functional and "turned to the left, and the fuse for INST must be good.

It would be rare, but it is actually possible, and HAS HAPPENED, that every single dimmer controlled lamp was burned out, perhaps from a bad voltage regulator surge, etc.

IF YOU do not have a wiring diagram, wander over to Mymopar.com and download the appropriate service manual and maybe the aftermalket wiring diagrams. Sometimes Dodge vs Plymouth is missing, so you will have to make do with the opposite manual


EDIT I see you have a 74, which is NOT posted there. I have a digital copy, and will give you one free, if you mail me a thumb drive and a return mailer.

 

[Mattax]

These shouldn't be too hard to figure out.
If you have a multi-meter it will help.
With the headlights on, did the high beam indicator light up? If so did it light up when the dipswitch was depressed?
Knowing this could help.

I like the idea of simple things first. Check the bulbs!

Some diagrams to go with what 67dart273 posted.

The headlight switch is really a multi-switch.
One circuit is the headlights.

Another is the parking and tail lights.
That has a branch inside the switch which goes to the adjustible resistance and then out to the 2 or 3 amp fuse in the fuse box, and then on to the instrument and radio lights.

#1 fuse is for instrument and radio lights

 

[Mattax]

If you have a multi-meter it will help.

For example, using the resistance setting on the meter, check the switch circuit that feeds the instrument lights.

With the bulbs out, measure high beam to ground and low beam to ground.

Also with the bulbs out, check the high beam wire to ground and the low beam wire to ground. Might be a short to ground thats tripping the circuit breaker. I've had one istance where the low beam wires chafed against the headlight bucket causing that type of short intermittantly.

 

[BornNaked]

Thank you very much. I will be doing some testing and will update when i van.

 

[Murray]

It may seem weird but I have seen all dash lights burned out and needed replacement.

 

[BornNaked]

It may seem weird but I have seen all dash lights burned out and needed replac

I have a a few extra bulbs I will try.


I do have an update. I have a power probe and limited knowledge at my disposal.

I can tell you that I get 12 volts on the red on the back of the cluster. I also get 12 volts on the black which is weird right? They are also hot to touch. My dad is stopping by (Retired electrician). to assist.

Maye a short somewhere?

 

[BornNaked]

Should all of these screws should be reading 12v?
All I get a a bit of flashing with my probe light

 

[67Dart273]

Should all of these screws should be reading 12v?
All I get a a bit of flashing with my probe light
View attachment 1716427157

Boy oh boy, where do I start?

First, PLEASE do not start probing around and "measuring" stuff when you don't know what it is/ does. If you don't know what to expect BEFORE you probe it, how do you know what you measure is correct? And how do you know you have controls/ switches set correctly for such a measurement?

Next, ya see that big red wire and the big black wire next to it? BOTH those are the ammeter circuit, are ALWAYS hot and are NOT fused except for the "fuse link" which is damn poor protection. And notice how rusty that connection is? That likely needs to be re--made, and it may be an indication of other problems in the dash/ cluster area, because of moisture

I told you the other day..if you do not have a factory shop manual...........

"EDIT I see you have a 74, which is NOT posted there. I have a digital copy, and will give you one free, if you mail me a thumb drive and a return mailer."

All this will cost you is postage to me and back, and the cost of a thumb drive.

 

[67Dart273]

What does your headlight switch look like? Does it show evidence of moisture? That can/ WILL get inside and compromise the contacts


I told you about the tan and orange down in the fuse panel. Did you measure that and what did you get?

 

[BornNaked]

After replacing the headlamp switch with a new one the center console light turned on but not the gauge lights. We ended up pulling the cluster to clean all of the contacts for the bulbs. After we did that, the we're working again.

I did have a few burnt out bulbs but at the moment. All of the gauge lights are now working as it should. So Im glad I went through the trouble

The high beams I will tackle next week end. Like I said, when I press the high beams switch, the headlamps go out. but just the head lamps, running lights stay on. I replaced the switch from a sugestion but still the same results.

 

[Mattax]

I can tell you that I get 12 volts on the red on the back of the cluster. I also get 12 volts on the black which is weird right? They are also hot to touch.

Weird only if you're thinking black is ground.
Black is not ground.
Power feeds in the car have Black as well as Red insulation. (The few grounding wires usually, but not always, also are black. You'll see an example on the headlight connector)

The car has two power supplies; the battery and the alternator. They are tied together with the main feeds at a welded junction. When the engine is running, the alternator is producing power at 14 to 14.8 Volts. Everything connected to the alternator output is at the voltage.

When the engine is off, all those wires are at 12 to 12.8 Volts, because they are all connected to the battery positive.

Maye a short somewhere?

Probably not.
If there was a short, the ammeter needle would probably have pegged D. D = 40 amps discharge. Lets talk amperes. Amperes are a measure of how many electrons are moving. Another way of describing amperes is current. Think of current you might think of a river. Same idea. The current of a river is the movement of water molecules and the current of electricity is electrons moving.

They are also hot to touch.

I assume by this you mean they are physically hot.

If they are hot that means two things
1) There is current flowing through those connections
2) There is resistance in those connections.

For normal starting there is about 5 amps discharge from the battery through the ammeter to the ignition. This will show as a small movement of the needle.
For normal charging there will be around 10 amps or less flowing into the battery.
And if you are doing some testing of the headlights and have the door open, there might be 10-15 amps going through the ammeter to the dome light, parking lights and headlights.
That amount of current should not cause heating of the ammter connections.
As was noted, there is visible corrosion on the nuts and studs.
1. Disconnect the battery.
2. Then disconnect the wires, noting how they aer supported, and also note if there are fiber or plasting insulating washers.
3. Deoxidize the connections (I like a fiber brush and de-oxit)
4. Gently check the ammeter studs for any looseness. If the ammeter studs are loose, they must be attached firmly with solder (or silver solder?) or the ammeter replaced. The looser they get the more heat they will generate for a given current. Higher current will cause more heat than low current. regardless, once they are loose, they will only get looser and the resistance will increase. Eventually there will be no connection.