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Headlight on,brakes of!headlights off brakes on

Old 10-25-2016, 11:56 PM
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Lightbulb Headlight on,brakes of!headlights off brakes on

Hi I run a grand Cherokee 2001 the Laredo I believe. I have in there a new set of tail lights. I just got the stock ones replaced, unfortunately no fancy upgrades.

When my headlights are on my brake light are off, ironically enough my license plate light stays on no matter what. But when my head lights turn off my brake lights work. This is the same rule reguardless of whether my high beams are on.

I'm not super mechanically inclined, but is this going to be a simple fix like a circuit?
Obviously not because it works when one doesn't and vice versa...

Idk help?
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Old 10-26-2016, 06:36 AM
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Was it doing this before you changed the tail lights? sounds like a bad ground, or a wire harness loose or wires improperly hooked up in tail lights. The headlight switches on these year model GC are solid running junk also.
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Old 10-26-2016, 08:28 AM
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Did this problem occur before replacing the tail lamps? Are the tail lights new or did they come from somewhere? Did you use your old bulbs or did you replace?


I would probably start by removing all the bulbs in the tail lights from the socket and then replace one by one until the problem re occurs to see if you have a bad socket or maybe the bulb itself is an issue.


If this doesn't sort the problem I think the harness comes down the driver side under the plastic in the rear quarter.


Other issues that could potentially bring this up perhaps the switch itself for the headlights but don't quote me on that. Obviously checked all the sockets by removing the bulbs is the easiest way to start.
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Old 10-26-2016, 12:31 PM
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Yea they are brand new and I had it switched on a shop to be honest XD and on that Sounds fair enough I should be able to do that. It only started happening after I had them swapped


Originally Posted by x00j View Post
Did this problem occur before replacing the tail lamps? Are the tail lights new or did they come from somewhere? Did you use your old bulbs or did you replace?


I would probably start by removing all the bulbs in the tail lights from the socket and then replace one by one until the problem re occurs to see if you have a bad socket or maybe the bulb itself is an issue.


If this doesn't sort the problem I think the harness comes down the driver side under the plastic in the rear quarter.


Other issues that could potentially bring this up perhaps the switch itself for the headlights but don't quote me on that. Obviously checked all the sockets by removing the bulbs is the easiest way to start.
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Old 10-26-2016, 01:43 PM
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These are aftermarket lights, I take it? Were they plug&play, or did they have to be wired in? Also I'm assuming you are talking about tail lights and not brake lights, correct? Do your new units have separate turn signal bulbs?

With the factory system, all 6 bulbs are the same and the way they are wired determines which filaments light up. What happens when you step on the brake, both with and without the headlights on? How about turn signals and reverse lights? Can you check how they function with the original housings back in?

This is very difficult to diagnose with a keyboard and not actually seeing it. Pictures would help.
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