Deano15

Hello all!

I'm having a very strange problem with my dash lights on my 63' and before I start to dig into the car I wanted to gain as much knowledge on this topic. I've read most posts with similar topics but they don't seem to be exactly what I'm about to describe. Here's what currently works WITHOUT the dash gauge light fuse installed:

1. Turn signal lights
2. High beam light
3. E Brake light
4. brake lights

I should also point out that while the dash light fuse is out I measured the voltage at the left post and I am getting a variable voltage when turning the rheostat on the main light switch.

Now when I install the dash gauge fuse and turn on the main light switch the tail light fuse immediately blows (and the dash light fuse is still intact). When I measure the voltage at the left post of the dash gauge and I get nothing.

I've read a few posts that say if there's something wrong with your taillights the dash gauge lights would not function to let you know (not sure if this is actually true or not but it does seem connected somehow).

Any insight on this issue would be greatly appreciated.

Thank you all!

Larry N. Johnson

Sounds like a wire crossed somewhere.
Do you have diagrams?

65GGvert

Check for a short on your tail lamp sockets or wires, or on your license plate light. The voltage for the dash lamp feeds through the headlamp switch before it goes through the dash lamp fuse, so if the tail lamp fuse blows, you lose the voltage to the dash lamp fuse. So, the tail lamp fuse can blow and still leave the dash light fuse ok, but the dash lamps won't work. The tail lamp fuse should be a 10a fuse, second from the bottom. Possibly a shorted socket or bulb at the rear. It could also be in the headlight switch. One thing I've seen that will cause it, if you put a single contact bulb in the tailight socket, it will short the 12v to ground via the metal base of the bulb. The license plate lamp should be a single contact bulb.

Deano15

Hello and thank you for the replies!

I do have schematics in a service manual so I'll be referencing them as I dig into this. One point that doesn't make any sense to me is if there's a short in the tail light area why would they function correctly WITHOUT the dash light fuse installed?

Dean

65GGvert

That's why I mentioned the amperage on the fuses. If you have too small a fuse in the tail lamp fuse, maybe the combo is too much. It should be 10a and the dash 4a. Make sure they aren't switched. The dash light fuse also feeds the light in the radio, make sure that connection is not shorted. If you have larger than a 4a in the dash lights fuse, you could have a short in the dash light circuit (or radio light) that causes too much total current through the tail lamp fuse..
If it worked before, that should rule out a wrong wiring, but on the surface it sounds like the wiring to the two fuses is switched. If you have diagram, you should be able to trace it down.

cartalker

Do the simplest thing first.
Check to make sure you have the correct bulbs installed in all exterior light locations. I've seen it whre someone forced the wrong bulb into the socket and It causes a direct short.

Deano15

Thank you again for the posts!

It sounds like there will more than likey be a short somewhere between the dash light and tail light circuits because the radio light works (when the radio is on of course) even without the dash light fuse in!

So if we're in ageement of this fact then the next question is where is the most likely location for this to happen?

Thank guys!

Dean

65GGvert

You still haven't said if you checked the amperage on the fuses and the bulbs in the tail lights for correct type. My 65 wiring diagram shows the light for the radio coming from the dash lamp fuse, maybe the 63 is wired differently. I don't think I can do anything more not seeing the car wiring.

Deano15

Hello 65GGvert,

The fuses that I've been using are 10A for the tail lights (second from the bottom of the block) and 4A for the dash lights (third from the bottom). As for the bulbs, I did that earlier in the year (I had a corroded contact inside the connector which needed to be cleaned) and all the bulbs there are correct.

I'll see if I can scan the diagram in the manual well enough to be of any use and attach them here (hopefully tonight sometime).

Thank you again.

Dean

65GGvert

Here's the 65 diagram I'm using.

Deano15

Hello,

It's been a while since I've had time to look into this problem I've been having as life has been CRAZY!

Anyway, I found that my light switch has a broken rheostat so I purchased a new switch. I connected up one light and applied a good gound to the cluster and the light illuminated! This was done with the rear body connector removed.

Now for the bad news, I noticed that the ground wire for the cluster, clock and storage compartment (glove box) are hot when the light switch pulled out (but not when the switch is in the off position).

Strangly enough the ground wire being sent back to the rear lights has the same origin as the ground mentioned above and is also hot but those rear light work perfectly WITHOUT the instrument cluster light fuse installed!

Here's a schematic of the 63 wiring if it helps.



Thank you!

Dean

rich5962

Is this a problem that always existed, or a new problem, or after new wiring or other related work?

12v on your Black/White ground circuit..... Is this with the rear harness body connector connected? If it is, and the fact your Tail fuse blows, appears you have a short between Black/White(gnd) and Black(tail lights). The short may be related the the common ground via the dash light filaments, which by removing the dash light fuse eliminates it.


In this type of failure, it's helpful to eliminate all related items and then add them one by one back into the circuit to help isolate the fault. Don't use a test light. Disconnect the battery. You need a ohm meter.

I suggest you remove......

(rear related items)
All tail light sockets and bulbs,
License bulb/wire,
Fuel sender wires,

(dash related items)
Clock connector,
Glove box ground wire(Blk/Wt at the Z-bar),
Cluster ground terminal.

Disconnect the rear harness body connector and use a ohm meter at the plug between Blk/Wt & Blk.

Rear harness conn side:
If shorted it may be in the rear harness. If not add related items one at a time and retest each time to isolate.

Dash conn side:
If shorted it may be in the dash wiring. If not add related items one at a time and retest each time to isolate.

Rich