My signal lights are not working on my 03 Sport 2.4L manual transmission and factory tow hitch, installed at dealership. Fuse 39 is blowing and I have determined that its is not the back-up switch. How do you test the flasher and or multi function switch? The flasher does work for the hazard light though.
Signal Light Issue?
- Thread starter Jeffreywp
- Start date
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Billwill
Full Access Member
Firstly you should try to obtain a 10 Amp DC circuit breaker from Radio Shack or similar if you do not already have one....blowing fuses can be pricey and a pain.
When does the fuse blow? As soon as you try using the turn signals or the backup switch or simply at random such as going over a bump?
This fuse 39 circuit does not go many places but you probably have one of the leads shorting to chassis or engine.
First pull out the defogger relay point "E"....remote chance of the relay having a dead short on its coil.
It is doubtful that the turn lights are faulty as the flasher unit manages to drive them without problems.
Disconnect the battery and use a Multi meter on OHMs to measure from points to ground/chassis for resistance..do not touch the leads with your fingers!
So looking at the wiring diagram page 8W-12-27...the Dark Blue/White wire coming off fuse 39 may be touching ground somewhere.
First disconnect the backup switch and measure the wire to ground/chassis with it in the backup position....should not go direct to ground but should go through the backup lamps! Good chance there is an issue with the tow package. Go to page 8W-21-5 to trace the wiring there.
Unplug the hazard switch completely, you will now have no hazard lights or turn signals but does fuse 39 blow?
Problem is most likely the backup switch shorting to ground on its way to the tow package circuitry or a problem with the back up lamp wiring itself..go to page 8W-21-5 to trace that area.
In case you do not have the wiring diagrams download the 2003 KJ Service Manual here..includes wiring diagrams: Index of /manuals/Jeep/KJ
If you do not come right I will upload some of the wiring diagram pages and we can go through them together.
When does the fuse blow? As soon as you try using the turn signals or the backup switch or simply at random such as going over a bump?
This fuse 39 circuit does not go many places but you probably have one of the leads shorting to chassis or engine.
First pull out the defogger relay point "E"....remote chance of the relay having a dead short on its coil.
It is doubtful that the turn lights are faulty as the flasher unit manages to drive them without problems.
Disconnect the battery and use a Multi meter on OHMs to measure from points to ground/chassis for resistance..do not touch the leads with your fingers!
So looking at the wiring diagram page 8W-12-27...the Dark Blue/White wire coming off fuse 39 may be touching ground somewhere.
First disconnect the backup switch and measure the wire to ground/chassis with it in the backup position....should not go direct to ground but should go through the backup lamps! Good chance there is an issue with the tow package. Go to page 8W-21-5 to trace the wiring there.
Unplug the hazard switch completely, you will now have no hazard lights or turn signals but does fuse 39 blow?
Problem is most likely the backup switch shorting to ground on its way to the tow package circuitry or a problem with the back up lamp wiring itself..go to page 8W-21-5 to trace that area.
In case you do not have the wiring diagrams download the 2003 KJ Service Manual here..includes wiring diagrams: Index of /manuals/Jeep/KJ
If you do not come right I will upload some of the wiring diagram pages and we can go through them together.
I didn't know they made circuit breakers for cars. The fuse usually blows when the ignition is turn on. The back up switch is not the issue. When I first pulled the back up switch, the fuse did not blow right away and I thought I has found the issue, but while waiting on a new switch with the old one disconnected, the fuse blew again. I will pull the defogger relay and see what happens. Is there a way to disconnect the tow package to see if that is the issue? All the exposed wires for the tow package look good with no visable damage. I do have a multi meter but I am a beginner. I will test to see if fuse 39 is going straight to ground, but sense it is blowing right away, I am fairly sure it is. When you said "measure from points to ground/chassis for resistance", I am not sure what you mean.
Thanks for you help,
Jeff
Thanks for you help,
Jeff
Billwill
Full Access Member
OK if you have the 2003 KJ Service Manual wiring diagram 8W-12-27 you will see fuse 39 which is blowing.
With the battery disconnected and fuse 39 pulled out and your meter set to Ohms put one meter lead onto the output of fuse 39..should be a Dark Blue/White wire. Other meter lead goes to chassis or engine. Make sure you do not hold the meter lead ends with your fingers or you will see a reading of your body's resistance.
The Ohm meter should show a fairly high reading ie. a couple of Mega ohms if you are not in reverse.
If the reading is nearer to about 1 Ohm then fuse 39 will blow.
You then need to one by one isolate which branch of this lead from the fuse is causing the problem.
First pull out the defogger relay in case the coil of this relay is shorted. The Locations section of the wiring diagram will show where this relay is located on the rear of the internal fuse panel.
Then disconnect the back up switch and check if this Dark Blue/White wire suddenly jumps up from 1 Om to a few mega ohms which means the error is along the line that the backup switch is on.
The hazard switch pin 8 is also on this Dark Blue White wire so pull off the hazard connector and see if this line goes up to infinity.
You can leave the hazard switch, defogger relay and back up switch disconnected and re-connect the battery....none of these items will work of course but the fuse 39 should not blow unless this Dark Blue/White wire is shorting to chassis somewhere.
With the battery disconnected again, measure this wire for resistance to chassis...this is what I mean by measuring point to point. If you do get a low resistance reading then you have to start cutting wires to see which branch is causing the short but first disconnect connectors C104 and the C100 to see if the short disappears..the location section will show you where these connectors are located.
With the battery disconnected and fuse 39 pulled out and your meter set to Ohms put one meter lead onto the output of fuse 39..should be a Dark Blue/White wire. Other meter lead goes to chassis or engine. Make sure you do not hold the meter lead ends with your fingers or you will see a reading of your body's resistance.
The Ohm meter should show a fairly high reading ie. a couple of Mega ohms if you are not in reverse.
If the reading is nearer to about 1 Ohm then fuse 39 will blow.
You then need to one by one isolate which branch of this lead from the fuse is causing the problem.
First pull out the defogger relay in case the coil of this relay is shorted. The Locations section of the wiring diagram will show where this relay is located on the rear of the internal fuse panel.
Then disconnect the back up switch and check if this Dark Blue/White wire suddenly jumps up from 1 Om to a few mega ohms which means the error is along the line that the backup switch is on.
The hazard switch pin 8 is also on this Dark Blue White wire so pull off the hazard connector and see if this line goes up to infinity.
You can leave the hazard switch, defogger relay and back up switch disconnected and re-connect the battery....none of these items will work of course but the fuse 39 should not blow unless this Dark Blue/White wire is shorting to chassis somewhere.
With the battery disconnected again, measure this wire for resistance to chassis...this is what I mean by measuring point to point. If you do get a low resistance reading then you have to start cutting wires to see which branch is causing the short but first disconnect connectors C104 and the C100 to see if the short disappears..the location section will show you where these connectors are located.
I only had a little time Sunday to look into this. Getting home after dark in the winter makes it hard to find time. The back up switch has been disconnected for a few weeks now and yesterday I pulled the rear defogger relay, put a new fuse in and it blew when the ignition was turned on. When I first read your instructions I was a little confused, but after just rereading them it makes sense to me now. I'm not fast, but I AM slow. Will likely be next weekend before I get to look at it again. Thanks for the info.
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