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Weird electrical issue

C

Coronet 14

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Having an issue with dash lights and interior lights. When you turn the knob to the left to what should dim the dashlights it brightens them. IF you turn the knob up on what should brighten them all the dashlights and radio lights go out. Switch would get really hot and blow the 5 amp fuse and the 20 amp fuse. So I got a new headlight switch and when I hooked it up and smoked it. Hooked up the old headlight switch and put a circuit breaker in and smoke started comming out of the voltage regulator. Iv'e figured out where the wires go but haven't found any problems. The headlight switch will get very hot and still will blow fuses. When the switches got hot all wires were cool to the touch. So what am I missing. This is on my 72 Coronet :BangHead: Thanks
 
Is weird.

Almost sounds like a hot wire, in your lights wiring, is grounded somewhere. The way the wiring runs, that could be under the dash, or even under the hood. Keep in mind, when you use any light switch, wires from it become 'hot'.
Might start by dis-connecting the battery, and use an ohm meter at the headlight switch plug. Unfortunately, to check all this right, you need to pull all your headlights, and tail lights. If they are in place, even your hot wires will show grounded. Check each wire at the plug for grounding, with wiring diagram in hand.

The lights harness has to be isolated, then see if any grounded wire shows, and find out why. Could be simply one wire in the system that has cut against a ground, shorting it.
 
Hmmmmm, I have an idea but let me ask a few questions:
- Does this happen only when the engine is running or does it also happen when you turn the engine off?
- Do you have the original ammeter in the instrument cluster?
- When you put in the new switch and it smoked, what part smoked? The round porcelin part right behind the knob?
 
Also, look to see if one of the dome lights is shorted. You are likely getting power shorted 'backwards' through the system from something.
 
The area behind the porclin plastic piece sparked and started smoking also if you play with the switch the interior light will work go out then come on. With the car running no dash lights either. Whe you turn the headlights switch up like you would normally do to brighten the dash llights thats when they go out switch gets real hot and fuses blow. If you have the switch turned all the way down you have lights and the switch takes longer to get hot You can turn it all the way to when the interior light comes on. Almost like something is wired backwards. When you turn up the headlight switch the lights should get brighter not go out and blow fuses. The only things disconnected are the ashtray light. Thought that was the colprut and my heater switch control panel.
 
Yep you are on to it with the 'backwards' comment.

I suspect that the alternator output has somehow gotten shorted to the instrument light circuit in the dash cluster. The alternator output goes into the dash and connects to one side of the ammeter and that is how it gets into this area. When that source gets into the dash ligths circuit, and you turn the dimmer to what should be bright dash lights, the resistnace of the dimmer rheostat (the porcelin part) is lower and the alternaotr is able to push more juic back through the dimmer rheostat. That connects back to the battery and the rest of the car's electical circuits via the instrument light fuse in the panel.

Do you have other electrical issues with this car, like the battery not charging right? Is the stock ammeter still in the car and hooked up?

Do you have a voltmeter? I think you need one as the normal circuit path from the alternator through the ammeter and then to the battery sounds like it may be screwed up also, the latearnaotr is trying to push battery chargin current back through the instrument light circuit. I would first start the car, and measure the voltage on the big output stud on the alternator at fast idel, and see if it is around 14 to 14.5 volts; you may find it is very high. But that needs to be tested so see if the basic charging path and connections to the charging system are intact.

I would also take out the cluster and carefuly inspect the wiring to it and see if you can find one of the instrument light wires shorted to another wire somethere in the harness.
 
BTW, the instrument light circuit goes several places:
- Instrument cluster
- Heater switch lights
- Ash tray light
- Cluster area light
- Ignition swith light

The last one is a good place for the the alternator output to come close to the instrument light circuit.
 
Update: Found power wire going to ground and a ground wire not hooked up properly. I took the plastic bezel off the instrument cluster and screwed the headlight switch to it and connected the metal bezel to the metal part of dash panel Didn't blow the fuses. But is the dashlights supposed to go out when you turn the switch up. The dash lights get bright if you turn either headlight switch i have toward the left to just before you get to turning the interior lights on. But go out when you start to turn the switch clockwise. Thanks
 
Ok sounds like you are on your way.

As far at the dimmer reheostats, they can get corroded and erratic and will go on and off at different places as you rotate them. This is due to corrosion in the dimmer rheostat itself or in the slider connections into and out of it. I have cleaned one up and replated contacts and got it working great again, but that is more than most people want to do. Putting in a new headlight switch is the easy way to fix it . Now that you have the other problems fixed, then maybe try another new headlight switch to get the dimmer working smoothly.
 
I smoked the new headlight switch so I'm gonna replace it. That switch I was using to diagnose the problem. The old switch which I thought where the problem was and the new switch worked the same way. Turn knob clockwise and dashlights go out. Where can I get a new ampmeter I don't trust this one since I know it smoked.
 
I guess I missed something..... the ammeter smoked too?

If you suspect the ammeter, then take the lugs off of both ammeter terminals and use a machine screw and star washers of the right size to bolt the 2 lugs tightly together and insulate them. Then find the Mad Electric site and read up on that.

It is starting sound like your wiring has enough wiring issues to merit some serious upgrade work before it gets worse. (Like melting and burning worse!)
 
The dimmer on the light switch is working as designed. Check the dinner switch for the head lights. It lives in a dirty environment. If you have fried an amp meter would be advisable to replace interior wiring harness. Amp meters are heavy duty items and will take more abuse than any wiring under the dash. Also check the fuse box for damage and bulk head connection. Alternator current flows to the battery not the ignition switch.
 
"Alternator current flows to the battery not the ignition switch." Actually not true. The main circuit goes through the ignition switch, amp gauge and fuse box/bulk head.
The amp gauge is a weak link in the circuit as is the bulkhead and the ignition switch connector below the column.
You can just put both wires at the amp gauge under one of the gauge terminals to bypass the gauge. Done it this way for 35 years on several cars with no problems.
Check the ignition switch harness connector below the column to see if it has burned.
Also if you want to remove the load from these weak links you can run a 10ga wire from the alternator to the battery.
 
It doesn't look like the amp meter burned up. Maybe I caught it in time. Been checking the wires haven't found fried ones yet. I will have to address the wires on the wiper motor. I hope i can find a good quality headlight switch and not crap.
 
Any...and I mean any...lights issue, can also be caused by a bad ground. Might want to check some of your light socket grounds, to be sure there's no issues. Lights grounds are usually at the body, how the light fixtures are mounted in.
Just causes a higher load on the hot side. Just wiring basics stuff.

But, sounds like you are finding some of your problems! Good to hear, and good luck with it.
 
..... send your cluster to bobs speedometer fir a test and have the amp meter soddered once you have a cross between hot and ground don't chance anything... check out the bulk head connection ... go through the entire wiring ... do the common up grades from mad electronic and listed here.. relay everything etc... or as mentioned above pick away at random issues as the pop up.. side of the road is nice place to sort it out in some fancy dinner clothes... or just except the situation and be doubly shure you have a strong wiring system... ron Francis is you're go to for this...
 
moparmarks said:
"Alternator current flows to the battery not the ignition switch." Actually not true. The main circuit goes through the ignition switch, amp gauge and fuse box/bulk head.
Click to expand...
Mmmmm... actually, alternator charging current to the battery does not go through the ignition switch.....but indeed alternator current (when being generated) does flow through the ignition switch to other loads.
 
The battery should start the car only all other loads come off the alternator... except for a audio amplifier to isolate the alternator whine ...
 
Thanks for the help. So far I've fixed two grounding issues. I did clean the bulkhead connectors.
 
nm9stheham said:
Mmmmm... actually, alternator charging current to the battery does not go through the ignition switch.....but indeed alternator current (when being generated) does flow through the ignition switch to other loads.
Click to expand...
Ya your are right. Was really tried last night and wasn't thinking right. Ignition is tapped off of the main circuit.
 
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