Hot Rods Electrical Guru’s help needed

Out of nowhere I’m blowing my 15 amp dash,tail and parking lamp fuse.
I can replace fuse pull the headlight switch and it all works fine in both positions,either parking or with the headlights on as long as the ignition is off.
Start the engine or have the key in the run position and pull the headlight switch and the fuse blows immediately whether the car is moving or not. The headlights remain on but I lose the dash,park and taillights along with the tag light in the trunk handle.
Everything looks good under the dash, the connections at the park and taillights (LED’s) are solid.
Should I be looking at the headlight switch or ?

 

Disconnect the stereo power connection, see what it does.

I'm grasping at straws, because it doesn't make a lot of sense

 

See if something metal has fallen on that terminal of head light switch, check switch for internal short, move on to all wires that are of that circuit.

 

With limit information it sounds like a module you are powering up with lighting when key is in run position is grounding your lighting circuit blowing the fuse.

 

You running an electric fuel pump?

 

I am not.

 

Original wiring harness??
The ignition power should be totally separate from your headlight power. At least that's the way I do it with a new harness.
The headlight switch power somewhere is grounding against something that's powered by your ignition

 

I had a similar problem with my old '32 mordor and after many blown fuses and even more rewiring I discovered I had a bad headlight switch, replaced the switch and never had another problem, the switch was about 15 years old. HRP

 

Some information about the vehicle would be helpful.

Are we working on an Edsel or an Oldsmobile ?

Oldmics

 

What he said

Ben

 

Sorry assumed everyone figured it was my 40 in my avitar .
Haywire harness in the car, GM type headlight switch with dimmer for dash and courtesy lights. Parking lights stay on with headlights
Headlights work even when running lights fail weather engine running or not.
As I stated fuse only blows when light switch turned on and the ignition is in run position or engine running.

 

Tell us about the ignition switch...where is it? On the dash or the column?

Maybe some pictures of the car would help...so we can see what you have that might be causing the problem. We really have nothing to go on.

 

This is a new problem ,right? HRP

 

I'd start by disconnecting the dash, tail and park lights one circuit at a time and then trying it. If it still blows the fuse, then the problem is in the switch or the power feed to it. Start tracing back from there...

 

You might get a circuit breaker in place of that fuse while you troubleshoot, to reduce the number of fuses you go through.

 

suspect the switch-as I recall that switch had two hot feeds as well. Try what Crazy Steve said 1st.

 

I'm wondering how a defective headlight switch would know the ignition was on and only blow the tail/dash circuit at that time?

Does it do the same if the switch is turned to accessory?

Is there anything else going on at the same time?

What is hooked to the tail/dash light circuit that could be affected by powering the ignition switch.
Squirrel mentioned the stereo; possible if the lighting is hooked up to the dash light circuit and switched by radio power on.

You can jump the fuse with a light bulb; which will save fuses during trouble shooting and go off when the short is found and removed (the fuse in attached pic isn't really needed).

 

Hell of a lot of suggestions but very poor information on the feedback.

 

My thought it's in the dash is it stock? Dash lights and gauges are the common denominator I can think of between lights and ignition. What happens if you turn the dash lights off?

 

My ? is this...has everything been ok, nothing added...suddenly started doing this? As others said, it should be two separate circuits.
You can easily fabricate something. Remove fuse and replace it with either a two prong flasher or an incandescent headlight (2 lights in parallel better). Use couple of leads, jumpered into fuse socket. From what you say test headlight(s) should be on when pull light switch, then real bright key in run position.
A flasher you can tell by rate of flash what's going on. Lights will flash when turned on, but do they stay on in run position?
Another try is an ammeter. Put it across fuse socket (analog needle ammeter is best) you can measure current. It may be, say, 10 amps lights on...then what does it go to in run position?

Sent from my SM-S320VL using Tapatalk

 

Spent the entire afternoon with a friend of mine who serviced the electrics in Chicago police cars until his retirement.
Rigged up a circuit breaker to limit the number of fuses the car would blow as we systematically went through each phase of the lighting system.
Ended up rewired the taillights and after eliminating the turn signal switch was the cause took it for a short drive where the breaker popped.
Long story short I’ll get a new headlight switch in Louisville.
Thanks to all who responded.

 

Year? Some had primary power that went into and back out of them.

 

I bet the power goes to the headlight switch, and then to the ignition switch. That is why it blows the dash,park and taillights, fuse. The headlights have a circuit breaker built into the switch, that is why they keep working. You have a short somewhere in either the ignition circuit or one of the accessory circuits. That is the only thing that makes sense with your scenario.

 

What the hell happened

 

Steering column shorts do wonky things too

 

THe correct term is ground not short. A short would be between 2 wires in a winding in a motor or a alt.rotor.

 

Oh Yeah,,,, as in a “short to ground”

Basically anytime, in fact every time current flows in an unintended path it’s a “Short” or “short circuit” but not all short circuits go to ground.

A short circuit is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit. The opposite of a short circuit is an "open circuit", which is an infinite resistance between two nodes

 

Electricians do it with no shorts

 

^^^^^ Boring if you don't feel a thing.