Voltage at Taillights 66 Dart?
- Thread starter coalman
- Start date
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If you have less than battery voltage you have a voltage drop ussue
67Dart273
Well-Known Member
...........X2.........UNLESS............the battery is nearly dead. What does the battery read? If battery is "up" then first place I'd check is the fuse box for corrosion, loose clip, even a defective fuse.
Your circuit path for the parking/ tail lamps is (assuming majority of vehicle is operating OK)
Fuse panel "hot" buss from ammeter---------through fuse---------to B2 of headlight switch connector------through switch----back out connector--------to the left kickpanel connector--------to rear harness--------to rear sockets
Each point in the above path is a possible poor connection
pishta
I know I'm right....
Got a point and shoot laser thermometer? To drop 9V, something will need to dissipate 3V of power and that can only be heat. you can shoot he suspect joints and switches to find a raised temperature. Disconnect the power feed to that circuit and remove the bulb and check OHMs on that line to ground, it should be OL (open loop) or 999Mohm. That is reading potential to ground. Any reading under 1Mohm would be suspect.
Back probe the connectors with pins or paper clips. Don't poke holes in the insulation to test. I have seen wires inside the insulation turn crusty white with corrosion 2 feet away from a wire poke.
67Dart273
Well-Known Member
Considering the "not very much current" NORMALLY in that circuit, that is a hell of a lot of voltage drop. LOL. You probably don't even need an infra-red thermometer. Just turn them on, leave them burn for a couple minutes, then feel around the fuse panel, the light switch, and the kick panel connector for heat. And smell LOL
Might also be you have a partial short somewhere drawing too much current. I assume, you did not say, that it is not blowing fuses
Might also be you have a partial short somewhere drawing too much current. I assume, you did not say, that it is not blowing fuses
Sorry didn't blow any...
Not that you should start there but often times it's the dimmer switch that causes that problem. I am better not to help diagnose electrical over the internet. I can't see what you see or don't.
Thanks, switch is pretty new...
67Dart273
Well-Known Member
You might want to tabulate "what doesn't" work in the car besides head and tail lights. Find the "hot" buss in the fuse panel and monitor that for voltage. See if it drops when you pull the switch
Check other stuff that should work with no key. Dome, brake, and park, tail, and hazard. You may have a major supply problem such as ammeter circuit
Check other stuff that should work with no key. Dome, brake, and park, tail, and hazard. You may have a major supply problem such as ammeter circuit
Thanks, I think the switch might have just quit. The rheostat was a little hot before the head lights quit. Right now I have 12.50 volts on battery, 12.39 at the 12 gauge red in ignition switch plug, and 12.39 on the Black/White stripe wire from the welded splice to light switch. I will check your recommendations when it gets light out. Thanks
I checked the continuity from L1 to L6 pulling the switch in and out, nothing to headlights. I am thinking of opening up the harness to check the welded splices for the low voltage, what do you think? Thanks
67Dart273
Well-Known Member
You are on the wrong track. L1 is headlights ONLY power. It does nothing else, and is a completly separate circuit for the headlights, which is B1 on the switch.
L6 is the power from P on the switch feeding the park lights. It gets power from B2 which comes from the fuse panel, that is wire L8
L8/ B2 feeds park, tail, and instrument lamps. L8 junctions there at the stop lamp switch, that terminal is nothing more than a branch, and so the wire from the stoplamp switch continues over to the fuse panel.
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I am not an electrical guru, which I am sure everyone knows, but this is weird to me.
I continuity checked the wires from the high beam switch to the bulkhead connector, and both L3 and L4 check 0 ohms no mater if you are checking X or Y for both wires.
Thanks
I continuity checked the wires from the high beam switch to the bulkhead connector, and both L3 and L4 check 0 ohms no mater if you are checking X or Y for both wires.
Thanks
67Dart273
Well-Known Member
You need to check under load if possible. A bad connection can sometimes check good for resistance. I realize that is difficult if it won't work. It is unlikely to be wiring, more right at the connection, AKA the crimp onto the wire, "let's say" at the dimmer switch, the actual connection from the connector to the dimmer switch, and the contacts right in the switch
Same deal in the bulkhead connector. Wire crimps, and connections right at the connector terminals. If you have not pulled the bulkead connector apart and inspected you should do that.
Same deal in the bulkhead connector. Wire crimps, and connections right at the connector terminals. If you have not pulled the bulkead connector apart and inspected you should do that.
67Dart273
Well-Known Member
I realize your frustration. Electrical has always come "naturally" to me. I helped out a bit first time when I was maybe 12-13. Some guys were tryin' to wire up a flathead V8 in a 30 something Ford. I'd never seen one. The solenoid and push button weren't wired. They did not have much, but had a test light and battery. I figured it out and hooked it up. They were amazed.
Even so, I've never done 'show' or 'aircraft' quality wiring that you see sometimes nowadays LOL
Even so, I've never done 'show' or 'aircraft' quality wiring that you see sometimes nowadays LOL
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