'Lectric question?

[slocrow]

While cruising home the other night I noticed that with my headlights on, in the bright position, the car developed a "intermittent short", I'm guessing.
The lights would dim or go out completely (I couldn't see while driving), the engine would miss and the dash lights would flicker off and on.
I closed the headlight switch which corrected the problem temporarily and when I pulled it back on the problem continued. I was able to eliminate the problem if I ran with the regular (low) beams on only.
It's an old style floor mounted headlight high beam switch that I'm using and it's mounted to the fiberglass floor.
Any ideas what's causing this and where I should look.
Thanks, Frank

[rick 36dodge]

The first place I would start is with a good ground.  
The second thing is your alternator is not keeping up with your demand, but if you have a 100amp alternator. It could be that you have everything going through your ignition switch. It can only handle about 60 amps. The fix it to put all your high amp draw items on relays (A/C , A/C compressor, A/C aux fan, headlights, power door locks, power windows and radio amps).
There is a lot of info on www.madelectrical.com  Go to the electrical tech section.
One more thing the headlight are pulling more amps than your circuit  braker can handle. That would cause the headlight to go off and on. Do you have the H-4 type headlights ?
I hope this helps.
Rick Harris

[Beep]

I'd bet ya $1.28 and a tall cold coke that it's your high beam relay or what we used call it, the dimmer switch. If it doesn't do it on low beam,,,I bet ya got a bad dimmer switch. Let me know.

[slocrow]

Thanks for the link Rick. A lot of good info.....

Beep; That's kind of what I'm looking for. A reason for it to start all of a sudden while never having had the problem before the other night.
I checked the grounds and everything seems to be status quo so I was leaning towards the light switch of the foot dimmer but didn't know if either had the capacity to cause the described result.
Hopefully other learned souls will chime in with conformation before I purchase a new one..................Thanks, Frank

[GPster]

Sounds to me like the high-beam terminal on the dimmer switch is shorted internally to ground. When the switch or any of the wires to the high beam terminal on your lights is in use it might be shorted to ground. Check your wires and turn it on high-beam and feel the switch and see if it gets warm. How big a fuse do you have on your lights? If it's power going to ground on that circuit it would be going through the fuse. GPster

[MrMopar64]

I had that happen on a 75 Duster with a floor mounted switch.....
Our best guess was that from lack of use the contacts inside the switch were corroded and when used would draw to much amperage...... Changed the switch and no more problems

MM64  

[Dave]

This better not be an excuse for you to not show up to Kzoo Buddy :?:
Gte out in the garage now and fix that thing  
Dave :(U)  :-}  :b-d:

[phat rat]

This better not be an excuse for you to not show up to Kzoo Buddy :?:
Gte out in the garage now and fix that thing  
Dave :(U)  :-}  :b-d:

He's out there, he called me a couple of hours ago from under it.

[Dave]

Why did he call you. I know stuff too :?:  Well i used to . Believe it or not I find my self at work trying to remember how I did a few things on the machines
:?:
I seem to be getting better but thats a wierd feeling............ :!:
Dave

[Jokester]

Once my car had a similar issue.  The lights would intermittantly go bright and dim (not hi and low beam, just brighter and dimmer).  I found that if I slowed the car down from 70 to 60 it didn't fluctuate at all.  Turned out to be an alternator problem.  It was alternating between overcharging and normal.  Higher rpm aggrivated the situation.

My 2 cents.

.bjb

[Dave]

2 cents accepted...  sent it to me Id like to retire    
Dave

[Pep]

If it just the switch, then all that would be affected would be the lights, so having it affect the engine as well would point to a source problem...eg, battery terminal or where the main feed connects to..like on the starter terminal. Or the earth connection from the battery...that's my guess anyway.

[phat rat]

Why did he call you. I know stuff too :?:  Well i used to .  

Are you really sure you want an answer too that question!!  

[Bruce Dorsi]

<snip>....I closed the headlight switch which corrected the problem temporarily and when I pulled it back on the problem continued.

I was able to eliminate the problem if I ran with the regular (low) beams on only.

It's an old style floor mounted headlight high beam switch that I'm using and it's mounted to the fiberglass floor.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
How about a wire between the high-beam side of the dimmer switch and the high-beam side of the headlights shorting to ground through a metal object?  ....Such as a chaffed wire at the headlight bucket, or along the frame?


Assuming that the fiberglass floor is eliminating any grounding of the dimmer switch, an internal malfunction of the switch would not cause a short to ground.

[slocrow]

Thanks for the ideas guys but I still haven't isolated the problem. Here's what I'm thinking and what I've changed out so far. Please correct me if you see a thinking error.
It's almost like I've got two problems that surfaced at the exact same time. Highly unlikely, I know.
One being the headlight high beam circuit and/or the second being a complete power failure. Either needs to occur for repeated brief and intermittent periods, while under power.
For reference, the headlight circuit is fused with a 30 amp, fuse size breaker, in the fuse box.
Since the incident I've redone the braided looms from the radiator shell to the headlight buckets with larger #6 fuel line, which has a larger ID so as not to crowd the 5 wires. In the bucket I've used permanent inline crimp connectors. At the shell I've used push pin, crimp type connectors for ease of future loom removal. New connectors in the bucket's only as I reused the wires. During replacement I found nothing loose or open.
I'm thinking that if I had a temporary,intermittent, short or grounding problem from the dimmer switch forward, on only the high beam circuit and if the breaker could rapidly kept resetting itself (doubtful) after each brief incident, that might explain the high beam headlights failing sporadically at quarter second intervals. However, as Pep pointed out, that wouldn't explain how the dash lights and engine juice also simultaneously failed.
That type of intermittent total electric failure begs a different conclusion. Why it's referenced to the headlight switch being on and the dimmer being in the bright position has me stumped.
I'll change out the $6 dimmer switch today and run the car tonight and report back tomorrow.
Thanks for the input and keep those cards and letters coming in...........Frank