Reverse lights blowing fuse

[Frank R]

My '04 Liberty, manual transmission, blows the reverse lights/turn signal fuse whenever the vehicle is shifted into reverse. It doesn't matter if the vehicle is running or not, so long as the ignition is on.

I haven't had a chance to start tearing into stuff looking for a cause yet, but was hoping some folks here might have some good ideas on where to start looking when I get to rip into this this weekend.

Thank you in advance.

 

[uss2defiant]

could measure the bulb holder with a DMM to see whether there's a short between the +12 and ground.

other than that maybe you're using the wrong fuse?

 

[Frank R]

The fuse is correct 10-amp mine blade fuse. I've gone up as high as 30-amp, just to see if it made a difference, and it fries those just as quick.

 

[uss2defiant]

sounds like a short.

You can also measure between where the fuse goes to a ground.
If you DMM has a continuity mode great, otherwise you'll hv to measure resistance.

Definitely disconnect the neg terminal of your batt before doing any testing.

 

[Frank R]

I have a multimeter - unfortunately I do not have the skills to use it. Mechanically, I can do pretty much whatever is needed but I'm about as qualified to do automotive electrical work as I am to do brain surgery. I'm really hoping for a very obvious problem.

Thank you.

 

[tjkj2002]

I have a multimeter - unfortunately I do not have the skills to use it. Mechanically, I can do pretty much whatever is needed but I'm about as qualified to do automotive electrical work as I am to do brain surgery. I'm really hoping for a very obvious problem.

Thank you.

Yeah a few specialized tools make finding your issue much easier and safer.




But for a manual trans you only got the reverse switch on the trans,fuse,wiring,and lights.Your only down to 3 that could be the issue......


--bulbs/holders
--wiring
--reverse switch


Start with the bulbs and holders,try new bulbs,look at the bulb holder for any signs of melting,and also look at the housing where the holder screws into for any signs of melting around the contacts.If any melting found replace.


If that doesn't help use the DVM/DMM set on Ohms to check the wires from the fuse(pull fuse out) to the tail light,should have continuity and be fairly low.You will need to make a long jumper wire and it should read less then 1ohm to account for DVM/DMM error and length of wire.


If that checks out then there is only 1 thing left,the reverse switch itself.

 

[uss2defiant]

I want to add to what I mentioned about finding a short.

The light bulb holder should have two contacts that the light bulb physically makes contact with.
Removing the light bulb use the multimeter to read the resistance between those two contacts.
It should be an O.L. or no values being read then you have a short. Look at link for the DMM usage to find shorts with measuring for resistance
LINK

You can re-verify this at the fuse terminal as well. Using one probe for ground and one probe where the fuse terminal. check both fuse terminals and it should be an open as well.

Do what I mentioned with the jeep not in reverse gear. The tests will be checking the wiring and the bulb holder.

If those check out fine, then engage jeep into reverse gear and check for the open at the fuse terminal to see whether it is the problem is with the reverse switch.

Again, disconnect neg batt. terminal before proceeding with any steps.

 

[CzarKJ]

The reverse switch is cheap and easy to change as well

 

[TheZombieNinja3]

Go with the reverse switch first. I had this same issue in my 04. blowing fuses like no tomorrow. replaced the switch and boom, done.

 

[Billwill]

You basically have all the required advise above.

First remove the two wires off the reverse switch and short them out to see if the fuse still blows....this could save you shelling out for a new switch.

The +12 volts basically goes through the reverse switch and expects to go through the reverse bulbs and hence to ground. What is obviously happening is that they are not going only to the bulbs but are shorting to ground somewhere.

If you have still have the fuse blowing while bypassing the reverse switch then download the KJ Service Manual here...includes circuit diagrams....use the 2003 KJ manual as it is close enough to your 2004! Index of /manuals/Jeep/KJ