Wiring plow lights

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chrisp2493

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Asking for a friend for his truck. He has an 04 2500 ram and has a plow hooked up. He made up a wire harness to connect into the driver side headlight plug. After a few days of working all of the sudden his headlights (low and high beams) won’t work. Parking lights, fogs, turn signals all still work. So with the stupid canbus system, will wiring extra lights onto the headlight circuit mess with the computer? I hooked a test light up to the driver side light power supply and it was basically flickering. These trucks don’t have a separate fuse or relay for the lights, I guess it all runs through the TIPM or FCM
 

Fergusontd

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Asking for a friend for his truck. He has an 04 2500 ram and has a plow hooked up. He made up a wire harness to connect into the driver side headlight plug. After a few days of working all of the sudden his headlights (low and high beams) won’t work. Parking lights, fogs, turn signals all still work. So with the stupid canbus system, will wiring extra lights onto the headlight circuit mess with the computer? I hooked a test light up to the driver side light power supply and it was basically flickering. These trucks don’t have a separate fuse or relay for the lights, I guess it all runs through the TIPM or FCM
When you cut into a factory wiring harness you can cause alot of problems. Im not an expert on much of anything but there is probably some guys on here that can tell you a way to do it. Good luck.

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justin13703

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The TIPM is extremely sensitive to additional amperage draws on the circuits. Tapping anything additional into a factory circuit on pretty much any post-02 Ram is a bad idea. It can mess all kinds of stuff up. The best way to do it is to wire them up separately on their own switch, and hope that the factory lights come back when you unhook it from the factory harness.

Also, please PLEASE don’t use a test light on any vehicle after like the 80s. They can very easily fry computerized components and if you “test” the wrong wire with one of those, it will set your airbags off. On top of all that, they really don’t tell you anything. You can’t tell the difference between 11 and 12 volts with a test light.

Didn’t mean to get off topic there, but every time I see that someone used a test light on a modern vehicle, I actually cringe.
 
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chrisp2493

chrisp2493

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That’s what I figured, probably had too much amperage and threw off the computer. They probably need to get it on a separate circuit.
 

justin13703

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That’s what I figured, probably had too much amperage and threw off the computer. They probably need to get it on a separate circuit.
Another way you can do it is to wire up a relay and use the factory headlight wire as a trigger to turn on the relay. Relays only draw amperage in the milliamps and the truck won’t even notice that.
 
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