Headlight Wiring Gone Wrong
 

Sorry this is so long, it's my first post here and I'm trying not to forget something.

I recently purchased a 2001 Dodge Dakota 4.7 4x4 for a hunting truck. Shortly after getting it I realized that I have no High Beam Headlights. Low Beam work fine, Fog Lights work fine, but when I switch to High Beam everything goes out. When I opened the hood to replace the bulbs I see 2 giant wires running from the passenger headlight to the drivers side headlight. Obviously someone had issues before but unfortunately I don't know what problems they had.

Here is what I've checked so far:

Continuity at the High/Low Selector Switch - Checked Good

Voltage at the Multi-Function Switch Connector (Grey plug behind steering Wheel) - Low and High are getting about 11.6 volts with all lights off. When I turn the Lows on, the Low Beam Wire drops to .5 and when I turn the Brights on the High Beam wire reads .5 -- Is this normal? I know I'm missing something but don't know what.

Voltage at the Bulb Connector - Low Beams is reading 10.5 -ish and High Beams read nothing... But I don't know where to trace the wire back to find the weak spot. About 4 inches from the headlight it disappears into a great wire abyss that I can no longer follow.

I know the wiring diagram looks like the wires run from the Switch, to the CTM, to the Headlights. I have no other electrical issues so I don't think it'd be the CTM?

Any help on this would be appreciated, I have a Haynes Manual but it hasn't been much help as of now.

Welcome to the forum Big Al.

Power for the headlights comes directly from the CTM - both high and low beams.

The connector you're measuring is a "sense" circuit. It should be closer to 0, it's grounded when you turn the light on. The ground location is on the left hand side of the dash, near where the dash "pivots" if you were to roll it for service. Follow the bundle from the CTM, connector 1, it splits, and one part leads to the ground. Make sure it is clean and tight.

Still could be a bad CTM.

Thanks for that, Dan, I will check that at lunch (assuming I can get into that kick panel to get to the CTM)

I'm assuming the 8 gauge wire (might be 10) that is running from one headlight to the other isn't stock? I just wish I knew what problem they were having in order to put that jumper on there. Seems like it would have to be one headlight went out completely.

It's not stock, guaranteed. Dodge only ran 18 gauge wire.

Likely one of the headlights stopped working. They then ran the wire to the other headlight to get it working. But, the load caused the driver circuit to fail in the CTM and now, no high beams.

Got the kick panel off and the ground looks very clean and is very tight. That leads me to my next question, is there a way to test the CTM to see if it's working properly? Can I test the wires with my piercing meter going into and coming out or is that a no no? Thanks again, I hope to get this resolved this weekend so I can stop worrying about it.

It's never a good idea to pierce the leads. There are no splices from the CTM to each headlight so if the CTM is working you should have power to the headlight.

There is no way to test the CTM itself.

If you get a rebuilt CTM (google them) you'll need to have your key fobs reprogrammed.