Fuse 39 blew, which supplies the reverse lights, the turn signal blinker and the rear defrost. After unplugging the back-up switch, the fuse quit blowing. I am not the best with a multimeter, but checked for continuity and the switch seems ok. No continuity until I press the ball in. What else could it be? The wiring harness seems to be intact.
Back-Up Switch and fuse 39
- Thread starter Jeffreywp
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I'm not familiar with the working of it specifically, but, if there is 12v in one lead, I don't think there should be continuity to ground on the other. That would be why the fuse is blowing.
It's just a normally open switch. press brake pedal, the plunger moves out (or in) and makes contact between the two wires. That sends power to taillights. Release pedal, plunger goes in (or out) removing the contact and transfer of power. Not sure which way it is.
I would say the non-12v lead is shorted to the body somewhere.
It's just a normally open switch. press brake pedal, the plunger moves out (or in) and makes contact between the two wires. That sends power to taillights. Release pedal, plunger goes in (or out) removing the contact and transfer of power. Not sure which way it is.
I would say the non-12v lead is shorted to the body somewhere.
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I am not sure, but I think the back-up lights are just grounded to the body, giving me the continuity. I jumped the connector for the back-up switch and the fuse did not blow, the blinkers still worked and the reverse light were on. so I am fairly sure it is the switch, which is not in stock so I get to do this again next weekend :favorites68: I think Jiffy Lube got transmission oil all over the switch.
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I am working on the back up light circuit, not the brake light. But thanks for your effort :favorites13:
It turns out it is not my back-up switch. It worked for a couple of days with the switch disconnected but eventually blew fuse 39 again. I put another fuse in with the reverse switch disconnected and the fuse blew immediately when the ignition was turned on. How can I disconnect the rear defrost to isolate the turn signal circuit to trouble shoot further?
Billwill
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I doubt it is the rear defroster itself that I s the issue....Fuse 39 supplies power to the Defrost Relay coil....not the output from the relay itself although there could always be a short of the lead from fuse 39 going to the relay coil going to ground.
More likely the lead going to the flasher unit or the flasher unit itself or the outputs from the flasher unit.
What year/model is your KJ so I can give you some more specific advice?
More likely the lead going to the flasher unit or the flasher unit itself or the outputs from the flasher unit.
What year/model is your KJ so I can give you some more specific advice?
The flashers work with the hazard switch. I believe the flasher is for both the hazards and the turn signals. I need to back up and cover all the facts. I do have a factory hitch that I believe was installed by the dealership for the PO. A couple of years ago, fuse 39 blew while I was towing my smoker. It did this twice, so I just quit plugging the trailer lights up when I towed the smoker and had no issues. This time it blew without towing a trailer, and when I replaced the fuse it blew immediately upon turning the ignition on. I was out of 10 amp fuses and tried a 15 amp that also blew immediately. After pulling the reverse light switch, the fuse did not blow right away and I thought I had isolated the issue. But while waiting on the new reverse light switch, the fuse blew again. Could the flasher work for the hazards and not the turn signals? The turn signal switch feels normal, how likely is it that the switch is the issue?
Billwill
Full Access Member
The Hazard switch has a fair amount of logic within itself and operates both the Hazard lights and the Turn lights.
Let me know what year/model your KJ is and I will look up the circuitry and advise you on what to check.
Let me know what year/model your KJ is and I will look up the circuitry and advise you on what to check.
Sorry I didn't include the info. I am on another car forum and am used to having that info included in the banner. I have a 2003 Liberty Sport with the 2.4 and manual transmission.
Does anyone have any diagnostic advice? Or if I am going to resort to buying new parts in hope of fixing the issue, which part should I start with? The multifunction switch feels normal when shifting between the positions and the headlights function properly. It is hard for me to see how a mechanical switch would cause a dead short. So my first guess would be the flasher. But the flasher works for the emergency lights. Could the flasher work for one and not the other?
Ljohn99
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Did you ever fix this problem?! I am having the same issues
Billwill
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Give us the exact details of your problem as it it may have some differences to the the original post.
What year/model is your Jeep?
Ljohn99
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2003 Jeep liberty renegade and my turn signals work but every time I put my car in reverse the fuse number 39 blows so I did some troubleshooting and I don’t think it’s my tail light housings or the bulbs in them I think it’s my reverse switch because when I unplugged my reverse switch it stopped blowing, when I had the reverse light bulbs out it
Blew
Billwill
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This is a bit difficult to fix if you are not knowledgeable with auto wiring but here goes!
Download the 2003 Jeep KJ Service Manual below.
I presume this is a Gasser with Manual Transmission.
Go to Page 8W-21-5.....you will see the Back-up Lamp Switch at the bottom of the page.
+12 volts goes onto the switch from fuse #39 via a Dark Blue Wire with a White Stripe....this should all be OK!
To check if the Switch itself is bad, pull off the Brown/Light blue wire from pin #2 of the switch so the switch should be floating in mid air. If switching ignition On and operating the switch blows the fuse then the switch itself has a fault inside it!
Then the +12 volts leaves the Back-Up Lamp Switch via a Brown Wire with a Light Green Stripe......somewhere here is a short to ground!
This Brown/Light Green wire goes through a lot of connectors before finding its way to the Left and Right Tail/stop lamps and Trailer Tow Connector.
You will need a Digital Multimeter....a cheap one will do as major accuracy is not needed. With the meter set to Ohms and ignition OFF, place one meter lead onto the Brown/Light Green wire at Back-Up Lamp switch pin 2 and the other lead firmly grounded to chassis/engine. Make sure you do not touch the lead ends with bare hands as your internal resistance with affect the reading.
You will expect to get some reading of resistance..a few Kilo Ohms, as you have the Back up lamps fitted. Remove these lamps and you should not have any reading but probably will have a reading of only a few Ohms as there is a short somewhere!
Find the locations of all the connectors that this Brown/Light Green wire goes through...the connector locations are shown near the end of the Wiring diagrams.
Start at the top ie. disconnect connector C310 while keeping your meter lead on pin #2 of the Back up Lamp switch. If the meter reading jumps up from the low-ohms being shown to a high ohms reading then the short is above C310.
If not, continue down this line disconnecting the connectors C306, C207 etc. until the shorted section is found.
So let's say that if C201 is opened up and you get a good reading above C201 but a bad reading below C201 then the wire section between C201 to C100 may be shorting to ground or the section between C100 to C105 is shorting etc.
Once you find the shorting length of wire, try physically trace the wire to look for shorting to engine/chassis. If the wire's insulation is damaged...try insulate it. If you cannot find where the wire is damaged because it disappeared into some hard to reach spot then you need to cut off the bad wiring at both ends and replace it with a new section by soldering and insulating it and wrap it up neatly with the existing harness.
If you do not wish to buy a meter, try get a DC 10 Amp Circuit Breaker to fit into Fuse#39's socket. Then you can disconnect the connectors one by one until the circuit breaker stops tripping.
I have found about 15 shorting wires on my Jeep after a front-end collision...most of the bad wires were unreachable so I had to cut off the wiring at all ends and replace with new wire!
Have fun!
www.colorado4wheel.com/manuals/Jeep/KJ/
Download the 2003 Jeep KJ Service Manual below.
I presume this is a Gasser with Manual Transmission.
Go to Page 8W-21-5.....you will see the Back-up Lamp Switch at the bottom of the page.
+12 volts goes onto the switch from fuse #39 via a Dark Blue Wire with a White Stripe....this should all be OK!
To check if the Switch itself is bad, pull off the Brown/Light blue wire from pin #2 of the switch so the switch should be floating in mid air. If switching ignition On and operating the switch blows the fuse then the switch itself has a fault inside it!
Then the +12 volts leaves the Back-Up Lamp Switch via a Brown Wire with a Light Green Stripe......somewhere here is a short to ground!
This Brown/Light Green wire goes through a lot of connectors before finding its way to the Left and Right Tail/stop lamps and Trailer Tow Connector.
You will need a Digital Multimeter....a cheap one will do as major accuracy is not needed. With the meter set to Ohms and ignition OFF, place one meter lead onto the Brown/Light Green wire at Back-Up Lamp switch pin 2 and the other lead firmly grounded to chassis/engine. Make sure you do not touch the lead ends with bare hands as your internal resistance with affect the reading.
You will expect to get some reading of resistance..a few Kilo Ohms, as you have the Back up lamps fitted. Remove these lamps and you should not have any reading but probably will have a reading of only a few Ohms as there is a short somewhere!
Find the locations of all the connectors that this Brown/Light Green wire goes through...the connector locations are shown near the end of the Wiring diagrams.
Start at the top ie. disconnect connector C310 while keeping your meter lead on pin #2 of the Back up Lamp switch. If the meter reading jumps up from the low-ohms being shown to a high ohms reading then the short is above C310.
If not, continue down this line disconnecting the connectors C306, C207 etc. until the shorted section is found.
So let's say that if C201 is opened up and you get a good reading above C201 but a bad reading below C201 then the wire section between C201 to C100 may be shorting to ground or the section between C100 to C105 is shorting etc.
Once you find the shorting length of wire, try physically trace the wire to look for shorting to engine/chassis. If the wire's insulation is damaged...try insulate it. If you cannot find where the wire is damaged because it disappeared into some hard to reach spot then you need to cut off the bad wiring at both ends and replace it with a new section by soldering and insulating it and wrap it up neatly with the existing harness.
If you do not wish to buy a meter, try get a DC 10 Amp Circuit Breaker to fit into Fuse#39's socket. Then you can disconnect the connectors one by one until the circuit breaker stops tripping.
I have found about 15 shorting wires on my Jeep after a front-end collision...most of the bad wires were unreachable so I had to cut off the wiring at all ends and replace with new wire!
Have fun!
www.colorado4wheel.com/manuals/Jeep/KJ/
Ljohn99
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Oh good god, thanks!
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