Dash Light Fuse Keeps Blowing!

[Ghostultramarine]

Okay, this is frustrating.

The fuse for the dash lights keeps blowing. It happens sometimes when the lights are first turned on.

It does not happen all the time.

I cleaned the ground wire from the steering column. I even ran a ground from the ground on the battery to the top left screw holding the dash in place (yes, the dash, not the chrome piece that goes over it).

I’ve even been using 5amp fuses as the shop didn’t have 4amp.

Any suggestions?

 

[Davea Lux]

There is a short someplace, the trick if trying to find it. I would pull the instrument cluster and start checking the lighting circuit pathways. Remember that the heater control also has a wire from the cluster circuit, that wire sometimes gets rubbed and shorted against other things under the dash. Also check your light switch and the resistance coil to the panel dimmer for shorts.

Dave

 

[Ghostultramarine]

This may sound like a stupid question, but HOW, exactly, should I be checking the circuit pathways?

I’m going to guess with a multimeter.

If so, what setting should it be on? Etc. Et al.

 

[Davea Lux]

This may sound like a stupid question, but HOW, exactly, should I be checking the circuit pathways?

I’m going to guess with a multimeter.

If so, what setting should it be on? Etc. Et al.

Use a multimeter to check continuity and resistance. A pathway that is shorted to ground will usually show a lot less resistance than one going thru a bulb filament. Use the resistance setting.

Dave

 

[Ghostultramarine]

Should I be doing this with the dash pulled?

 

[Davea Lux]

Should I be doing this with the dash pulled?

That would make the job a lot simpler and you can do a detailed inspection of the cluster that way. You might also try turning the dimmer to the full on position, that disengages the resistance wire in case it is shorted. You might also check the lighting leads to the heater control and the clock to be sure they have not gone to ground from the wire rubbing on something before you pull the cluster.

Dave

 

[Chrome58]

I’ve even been using 5amp fuses as the shop didn’t have 4amp

This could be the problem.
You allow 1 amp more than the OEM fuse allowed.

 

[Ghostultramarine]

It was doing this before I bought the 5 amp fuses.

It should be harder to burn out a higher amp fuse, no?

This is for an A body, but I suppose doing something like this. (I fell asleep watching it so I’ll have to try to finish it, I guess.)

 

[Big_John]

What you have is some high resistance causing increased load in the circuit.

It could be a short, but I doubt it as that just blows the fuse all the time.

More likely, it's a bad connection in a plug, socket, bulb, wiring, light switch, or in the dimmer switch. My bet is on the dimmer switch or light switch.

Once question not asked.... Do you have any add on gauges with more bulbs tied into the circuit? Have you changed the bulbs for "brighter" (higher wattage) bulbs? Ok, that was 2 questions...

Do you have problems with the dimmer working correctly? OK, 3 questions... But that's probably the most important. They build up resistance, don't really adjust the lights correctly etc. over the years. They can sometimes be cleaned, or there are replacements and we gotta guy that rebuilds them too (my suggestion) @Devinism

One "work around" might be to use a "slo-blo" fuse. You'll probably have to search a little and match the length. I hesitate to suggest it, but since it's often when you first turn the lights on (which suggests a dirty switch contact) the slo-blo fuse would absorb the initial "shock" (pun intended) to the circuit and still not let the car burn down if there is a bad problem. Choosing between Slow Blow and Fast Blow Fuse for Power Circuit Protection

The other issue, worthy of note, is the quality of new, offshore fuses. I can't help but wonder about that in a 5 amp fuse. Is it just a crappy fuse? I have a supply of old Fusetron and Littlefuse fuses I've accumulated over the years, but I'm going shopping for more one of these days.

 

[Chrome58]

It should be harder to burn out a higher amp fuse, no?

Yes, of course. My misunderstanding.
I thought you said the dash lights kept burning, not the fuse.

 

[Ghostultramarine]

1) No brighter bulbs (I replaced them all with new stock numbers)
2) No gauges added
3) I've not played a lot with the dimmer - the *()$# fuse keeps blowing ...

Since it (the fuse) blows/burns out when the lights are turned on and not a thing else is touched or turned, that would, in my mind, indicate I should start there.

 

[MrMoparCHP]

Factory Radio?


Alan

 

[rapidtrans]

You never know what you’ll find. I hate diagnosing auto electrics.
Years ago I had a 73 Charger doing the same thing. I would occasionally blow the fuse for dash lights, rear lights and what all. Replace fuse and I’m good for a few days then they’re out again. Finally I got frustrated and found a decent wiring diagram for the car and started visually inspecting entire circuit. Behind the passenger kick panel below dash I found a finishing nail behind the seat belt relay buzzer thing laying across the prongs plugged into the harness. The short! I found about a dozen of these nails under the dash and kick panel. Apparently the previous owner had tossed a handful of nails on top of the dash and forgot about them.

 

[MrMoparCHP]

When did this start? had you done any work or make any changes around that time?


Alan

 

[Ghostultramarine]

Well, I bought the car 2 months ago. I've been working with this since I got it (well, since I cleaned the fuse box connectors, changed the bulbs in the dash and fixed the dimmer so the dash lights would even work).

It is the factory radio.

I never thought about looking behind the kick panel for anything. I just had them off to repaint them, too.

 

[MrMoparCHP]

Year? Model?

Alan

 

[Ghostultramarine]

Sorry, 1968 Newport convertible.

 

[Big_John]

fixed the dimmer so the dash lights would even work).

What did you do to fix the dimmer?

 

[Ghostultramarine]

Post #41 in here:

No Brake Lights, But Turn Signals Work

 

[Big_John]

Post #41 in here:

No Brake Lights, But Turn Signals Work

Bingo!

"I glued the spring in"

The "spring" has to connected and not just glued in place. That's a resistance coil where the wiper arm moves up and down. When there's more resistance, the lights are dimmer.

So, if there's more resistance than that fuse can handle, the fuse is going to blow.

Probably just enough contact to kind of work, but not enough to work correctly.