No Cluster Lights

[Fox Slaughter]

I just got my 74 Challenger Wednesday and its not a show car so it needs some work.
First the gauge cluster doesn't light up at all.
The turn signals light up but thats it.
This is my first Mopar so I don't know where to start.

Tried dimmer switch both ways and still nothing.

Anyone have a write up on how to take the dash apart so I can get in there and check it out?


EDIT:

Haha being a Chevy guy I just found out there is a light bar that lights the gauges.

Found a website on how to take apart the dash so will report back once I get it apart and figure out whats going on.

 

[challenger6pak]

I would guess that something is wrong in the wiring or you need a dimmer switch rebuild.

 

[Fox Slaughter]

Do you know where the fuse block is located? I can't seem to find it haha.

 

[moparleo]

Look down at the firewall under your feet from the drivers position.

 

[Fox Slaughter]

Tucked to the left of the brake I'm assuming?

 

[moparleo]

Electrical gremlins are quite common on the old Mopars. After you find the fuse box, the thing to do is to disconnect the fuse block and clean all of the electrical contacts with Contact cleaner and a small wire brush. Get a tube of "Dielectric grease " and coat each plug in/ fuse contact with this grease. It will seal the electrical connections from any moisture and will eliminate future corrosion. It is good to check all electrical connections that you have access to such as, headlights, side marker lights, tail lights , firewall harness connection at the engine side of firewall etc... A great time to replace all of the bulbs since you will remove them to get to the sockets. Be sure to avoid the cheap Asian bulbs. The best quality are nickel plated if you can find them. Check at an auto parts store that specializes in German import cars. BMW's and other high quality cars use only nickel plated bulbs because of corrosion.

 

[Fox Slaughter]

I found it. It's to the right of the steering column above the brake. The fuse in position 5 is blown.

 

[Fox Slaughter]

Electrical gremlins are quite common on the old Mopars. After you find the fuse box, the thing to do is to disconnect the fuse block and clean all of the electrical contacts with Contact cleaner and a small wire brush. Get a tube of "Dielectric grease " and coat each plug in/ fuse contact with this grease. It will seal the electrical connections from any moisture and will eliminate future corrosion. It is good to check all electrical connections that you have access to such as, headlights, side marker lights, tail lights , firewall harness connection at the engine side of firewall etc... A great time to replace all of the bulbs since you will remove them to get to the sockets. Be sure to avoid the cheap Asian bulbs. The best quality are nickel plated if you can find them. Check at an auto parts store that specializes in German import cars. BMW's and other high quality cars use only nickel plated bulbs because of corrosion.

I get dielectical grease for free. Perks of being a lineman haha

 

[Fox Slaughter]

Alright on a 73 fuse block it says position 5 is for the gauge lighting. Tomorrow after work I'll have to look again and see if it's the orange wire that fuse feeds.

 

[moparleo]

Well then. no excuses. The first major fix you will do on your car is the electrical system.:wave:

 

[Fox Slaughter]

Haha oh joy.

It's taking away from my 76 k5 restore haha. The TH350 is laying in pieces in my garage.

 

[Fox Slaughter]

Well I pulled the gauge cluster light bar or whatever you want to call it. 2 bulbs were black, one tested fine even through it was black with a continuity test. Other bulb was burnt out.

The wires I have is orange going to the cluster lights then a light on the driver side overlooking the switches with a blue cover is yellow wire with a black tracer.

Now looking at the diagram all the bulbs are grounded at the bulb somewhere. So is it the plate itself is the ground, since there is only one wire going to each light. I'm assuming every bulb must have to work in order for any of them to work?

 

[Fox Slaughter]

Changed out the bulbs, no such luck.

If I check across the gap with the fuse out, lights on, I only get like 1v or less. Same with the fuse in. So this is telling me the ground is missing. I need to check the tan side to see if its getting 12v potential on it, if not that means its on the tan wire somewhere.

 

[moparleo]

99 % of the time it is a problem with the grounds.

 

[Fox Slaughter]

99 % of the time it is a problem with the grounds.

That is correct but in this instance it isnt. From the Orange side of the fuse to the radio power I get 12v potential which means the grounds are good. But from the tan side to the orange side I get nothing.

I just pulled apart the dash and took the dimmer switch out. Cleaned it and checked it out and used the Ohm meter to check that it was varying resistance. Which is was so I checked to make sure I was getting 12v into the rheostat and it is.

So this leads me to the conclusion that somewhere between the fuse block and the rheostat the tan wire is cut or something.

EDIT:

Just had an epiphany, when I was testing the rheostat I noticed if you moved it around like pushed or pulled slightly it would shoot the resistance up to like 100 ohms. So I am going to try wiggling it around.

Will probably just end up picking up a new rheostat.

EDIT EDIT:

Just realized now that the dash is back together I could of continuity checked the tan wire to the fuse block and it would of told me if the wire was cut/broken.

Argh.

 

[Fox Slaughter]

Tired of Editing the same post.

Alright just made a jumper and jumped from the radio power to the orange side of the fuse. Guess what, the lights worked.
So this leaves two things.

First I will have to take apart the dash again so I can continuity check the tan wire from rheostat harness to the fuse block. If that checks out its the rheostat.

If it fails then the rheostat could be good and the tan wire will have to be traced out and repaired.

 

[challenger6pak]

That's the only way to do it. Test one thing at a time until you find it.

 

[moparleo]

Electrical is so much fun.

 

[Fox Slaughter]

Electrical is so much fun.

I work on the power lines for a living and its much easier than car electrical.

 

[BoomerSoonerVA]

I have the same thing in my 72 Challenger. I cannot get the cluster lights to work. Open everything up and checked all wires. Is there some type of ground that should be there? I know the orange wire to the floor shifter light is not connected. Any leads will be great.