nm9stheham
Well-Known Member
Happens to me more than I would like it to! lol
Weird electrical issue
- Thread starter Coronet 14
- Start date
Coronet 14
Well-Known Member
I think I may have a bad voltage Limiter The voltage coming out of it is very erratic and not 5 volts. Once a get a stable voltage reading it reads 8 volts. Also I've got two wires coming off the pigtail on the back of the instrument cluster that go to the instrument cluster themselves. When I check them for power my testlight flashes. These are not the wires for the turn signals. One wire is violet and goes from the pigtail to circuit board Temp gauge and the other one is Blue goes to printed circuit board fuel gauge. The time delay for the ignition switch light gets burning hot I took off the case and the tip was black with blue at the end. Contacts look burnt When I turn the headlight knob clockwise the outside lights on the car go out Is that that supposed to happen Also killed the battery
Last edited:
mopar 3 B
Well-Known Member
Voltage from the limiter is not constant to temp or fuel sending units. A test light should flash if it is working properly. Are you testing voltage with a digital or analog meter? Voltage should be about 6 volts.
Coronet 14
Well-Known Member
Digital Meter The output side of voltage limiter is 8 volts.
miller
Well-Known Member
Question...the wiring harness(s) on the car, are they after-market?
At any rate, I'd consider checking each separate wire on your under-dash harness. Even two wires swapped can really toss a wrench into the works. Really sounds like something not wired right, since you've already found 'some', easily can be more! If things are wired wrong, easy to cook some of your switches, and such, and you'll keep cooking any part you replace.
Got a good wiring diagram for the car? It will be your best friend, for all that wiring. You need to know that all is hooked up right. Best of luck!
At any rate, I'd consider checking each separate wire on your under-dash harness. Even two wires swapped can really toss a wrench into the works. Really sounds like something not wired right, since you've already found 'some', easily can be more! If things are wired wrong, easy to cook some of your switches, and such, and you'll keep cooking any part you replace.
Got a good wiring diagram for the car? It will be your best friend, for all that wiring. You need to know that all is hooked up right. Best of luck!
Check the wiring at your door switches - this can cause problems in that circuit.
Coronet 14
Well-Known Member
The door switches are my next stop. There are no burn marks on the back of the fuse box. Right now I'm trying to figure out if when you turn the headlight up clockwise the outside lights are supposed to go out. When they are turned on. Then when you turn the knob down counter clockwise with the knob pulled out they come on. I ordered a new voltage limiter. Thanks for the help Guys/Girls
Coronet 14
Well-Known Member
Well I've narrowed it down to the miscellaneous circuit. I'm getting 12 volts but 32 OHMS. The longer I leave the headlight switch out the higher the OHM reading. What do they mean by switch title lamp
nm9stheham
Well-Known Member
Coronet14, The pictures you show are not of the voltage limiter; that is a signal or hazard flasher of some sort.
The violet and blue wires from the 2 guages ARE showing the voltage limiter operation if your test light flashes from each of these 2 wires. The limiter feeds into both guages within the cluster and the pulsed voltage flows through the guages and out to the sensors. When disconnected from the sensors, the voltage through the guages alone will pulse on and off at the full limiter voltage, which is battery voltage. It will switch on and off between 12V and 0V, dwelling slightly longer at 0v, with the average being 5v.
The headlight switch issue with the lights going out when you turn the knob again says that there is a short from the charging and main battery circuit to the instrument light circuit and power is feeding backwards through various circuits. You need to pull all connections apart, and start tracing power through the main power wiring first and then add circuits one at a time.
The violet and blue wires from the 2 guages ARE showing the voltage limiter operation if your test light flashes from each of these 2 wires. The limiter feeds into both guages within the cluster and the pulsed voltage flows through the guages and out to the sensors. When disconnected from the sensors, the voltage through the guages alone will pulse on and off at the full limiter voltage, which is battery voltage. It will switch on and off between 12V and 0V, dwelling slightly longer at 0v, with the average being 5v.
The headlight switch issue with the lights going out when you turn the knob again says that there is a short from the charging and main battery circuit to the instrument light circuit and power is feeding backwards through various circuits. You need to pull all connections apart, and start tracing power through the main power wiring first and then add circuits one at a time.
Coronet 14
Well-Known Member
I just posted pics of the time delay switch to show that the tip inside was burnt. It didn't show up very well. Tomorrow I'm starting at the marker lights then the taillights and the license plate light. I'll keep you guys posted on what I find.
Coronet 14
Well-Known Member
Found this inside my steering column
nm9stheham
Well-Known Member
That orange wire feeds from the igntion switch to the dome lights, etc, and also feeds through the fuse panel to the instrument light fuse and on to the instument light circuit (through a tan wire to the headligth connector). So that is a sign that there is system power being fed backwards from the instrument circuit into this circuit and very likely back through dome light fuse into the whole main electriclal supply system.
This would explain why you see various lights get brighter when you turn the headlight switch counter-clockwise (post #27); turning that knob CCW lowers the instrument dimmer rheostat's resistance lower, allowing more power to be backfed into the whole electrical system, including these lights. You could confirm or deny this by putting a voltmeter on either end of the instrument light fuse; the voltage would go up as the knob was turned CCW.
One other possible cause for this is not a short in the insturment light circuit but a missing ground on the instrument cluster. If this was the case, then when the other lights that get brighter with the dimmer being turned CCW, then the instrument lights would get brighter too. But the reheostat would never get hot if this was the case, so I still think there is a short to the instrument lamp circuit from the main power output of the alternator (or maybe the battery feed).
Have you checked the fusible link from the starter relay's big lug to the firewall connection? That being blown along with another short could be making current to flow backwards where it should not.
Also, have you checked all around the fuse block front and back for shorts? The instrument fuse should not be big enough to allow a lot of current to flow through it, but there could be a short in that fuse block (or the wiring to/from it), or the fuse has been replaced with one that has way too large an amperage rating.
Bottom line: You still have short somewhere. Keep examining the wiring. Tedious but necessary....
This would explain why you see various lights get brighter when you turn the headlight switch counter-clockwise (post #27); turning that knob CCW lowers the instrument dimmer rheostat's resistance lower, allowing more power to be backfed into the whole electrical system, including these lights. You could confirm or deny this by putting a voltmeter on either end of the instrument light fuse; the voltage would go up as the knob was turned CCW.
One other possible cause for this is not a short in the insturment light circuit but a missing ground on the instrument cluster. If this was the case, then when the other lights that get brighter with the dimmer being turned CCW, then the instrument lights would get brighter too. But the reheostat would never get hot if this was the case, so I still think there is a short to the instrument lamp circuit from the main power output of the alternator (or maybe the battery feed).
Have you checked the fusible link from the starter relay's big lug to the firewall connection? That being blown along with another short could be making current to flow backwards where it should not.
Also, have you checked all around the fuse block front and back for shorts? The instrument fuse should not be big enough to allow a lot of current to flow through it, but there could be a short in that fuse block (or the wiring to/from it), or the fuse has been replaced with one that has way too large an amperage rating.
Bottom line: You still have short somewhere. Keep examining the wiring. Tedious but necessary....
Coronet 14
Well-Known Member
She is getting there. Classic industries sells the 72 B body front and rear light wiring harnesses. I plan on rewiring after Christmas. I've learned a lot from working on this car and from the people here. Thanks for the help to everyone on here.
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