No. 4 fuse keeps blowing...

[Grec]

1973 Challenger Rallye.

No. 4 fuse was blown. Replaced it and instantly it sparked and blew.

Not good.

This is the 20 amp fuse that protects the parking lights, taillights, dash lights etc.

Is there a usual culprit?

I'm thinking shorted bulb wiring somewhere, but before I started tearing the car apart I figured I'd ask.

[Grec]

Also...

Blown bulbs woluldn't cause this, would they?

I found two parking lights out. Front right and rear left.

[ROMI]

If I were you, I'd check them all for corrosion. Usually prevents bulbs from lighting but depending on how bad and what's in there it can cause a short too.  After cleaning thoroughly, reinstall bulbs with dielectric grease.

[OUTLAW]

Burned out bulbs are considered an open circuit only  a short to ground will blow a fuse as you described. As stated above corrosion can become a direct short. I would start with removing all the bulbs and see if it still blows the fuse. If so then it is in the wires or switch.If not then you have a filiment that is shorting in one of the bulbs (not common but it does happen)
Most likely culprit is the headlight switch (popular to crap out on mopars)also check dimmer switch the wires run under the carpet and can short to the floor plate. To check the headlite switch reach up and unplug the connector and reinstall fuse if it dont blow you found it most likely.

[Grec]

Gotcha.

By-the-way... my headlights themselves are working.

Possible for the switch to be bad on just the middle position?

[Chryco Psycho]

it can blow if the wrong bulb is installed , could be a short in a wire as well , generaally the switch will not be bad in the middle position only & the headlights are not fused except with the fusable link under the hood

[Grec]

Lights are working now.

Most of them at least.

Working:

Front lower valence
Front drivers parking
2nd from left rear
Pass. rear parking

Not working:
Front pass. parking
Rear drivers parking
2nd from right rear

I don't even know how the tailights are supposed to be on these. Are all 4 supposed to come on with the parking lights?

My rear turn signals are working by-the-way.

I'm assuming that I simply have some bad light sockets and need to splice some new ones in.

[Chryco Psycho]

noonly 2 of the  4 tailights should come on with the park lights

[Grec]

OK. Cool. I onlyt have one to worry about then.

I'll check the socket out.

Two of my taillight bulbs were totally rusted out and corroded.  One of the sockets was fine, the other had oxidation/corrosion on it. May just need a good scraping.

Cheers.

[MEK-Dangerfield]

That's what it sounds like. These sockets need a good clean contact with the body of the car for the ground connection.


  Mike