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George H.
George H., ASE Certified Technician
Category: Jeep
Satisfied Customers: 18817
Experience:  ASE Master Tech 15+ years
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Grand Cherokee Orvis: I have problems with my trailer lighting.

Customer Question

I have problems with my trailer lighting. I have a '95 Grand Cherokee Orvis Edition. Trailer clearance and tail lights work as well as electric brakes. All other lights do not work
Submitted: 2 years ago.
Category: Jeep
Expert:  George H. replied 2 years ago.
Hello I will help you with your question, Do all lights on the vehicle work and it is only the brake and turn for the trailer that do not work? Which connector do you have? Flat 5 or round 7 pin? Do you have a 12 volt testlight or a voltmeter to check the circuit if I guide you?
Customer: replied 2 years ago.
All vehicle lights work. Only the trailer turn/hazard and brake lights do not. I have test equipment and have have the 7 pin connector. I had discovered a burnt out 10 amp vice 20 amp fuze in the number 1 spot in the fuze block. I replaced it with a 20 amp fuze and still do not have a fix. The 20 amp fuze is still good. I have no voltage to the effected pins on the 7 pin connector.
Customer: replied 2 years ago.
I'm thinking that the relays may be bad but have been unable to determine their location.
Expert:  George H. replied 2 years ago.
Can you open the left rear quarter trim and see if you have a lamp outage box mounted there? If you do the connectors are such you can unplug the box and connect them end to end bypassing the box. Let me know if that helps and if it does not we can work on the individual circuits. Let me know if you have questions about how to get to the outage module. Thank you
Customer: replied 2 years ago.
I'll check and get back to you.
Expert:  George H. replied 2 years ago.
OK, the relays are on the right side but they so rarely fail I think it will be something else.
We will find it eventually.
Customer: replied 2 years ago.
I bypassed the module, but symptoms persist
Customer: replied 2 years ago.
I've switched to my smartphone because PC decided to freeze up.
Expert:  George H. replied 2 years ago.
OK, on the right side (you can put the module back in) the relays are mounted almost on top of the wheel well and connector C331 is on top of the well. Start by checking for power and ground at the connector on the black wire and that the light green and the tan wire flash voltage with the turn signals
https://dl.dropboxusercontent.com/u/26725849/c331.pdf
I don't know if you can copy and paste that link on your phone but give it a try
That is the pinout for C331 and the diagram for the relays.
Let me know what you see at the connector then if you have everything there we can check the outputs of the relay and if those are right check between the relays and your trailer connector.
Let me know how I can help
Thank you
Customer: replied 2 years ago.
Is that on top of the rear or front wheel well?
Expert:  George H. replied 2 years ago.
The right rear is the location of C331.
Customer: replied 2 years ago.
Thanks. Checking.
Expert:  George H. replied 2 years ago.
Great, no need to reply unless you have test results. I plan on being here all evening.
Customer: replied 2 years ago.
I have continuous power to pins 1-5 whether iv,ition is on or off
Expert:  George H. replied 2 years ago.
Can you try keeping the connector connected and probing from the wire side? Use a straight pin to make contact inside the connector.
If you had power (12 volts???) on all those wires the turn signals would be on.
Do you have 12 volts on the black wire?
Customer: replied 2 years ago.
Sorry, was using continuity checker before and thought the black wire was ground. Checked again with multimeter. 12 volts to the black wire against ground on body. No voltage on the other pins.
Expert:  George H. replied 2 years ago.
Good, now check the connector and see if you have 12 volts to the black pin there.
Customer: replied 2 years ago.
Will do. Also I am getting flashing voltage for LT on pin 4 and RT on pin 5
Expert:  George H. replied 2 years ago.
OK, so you know the turn signals are getting there. The black wire at C331 changes to a black/red stripe wire at the 7 pin. Let me know what you find Thank you
Expert:  George H. replied 2 years ago.
Sorry, the black wire at C331 changes to a red/black at the circuit breaker and back to black at the splice so it is black at the 7 pin.
Customer: replied 2 years ago.
Ok I need to backstep. on C331 coming off of the wiring harness I was getting 12 volts on pin 1 the red wire. After reconnicting the two halves of C331, shold I begging 12 volts on pin 8 the black wire with engine off or on?
Expert:  George H. replied 2 years ago.
Pin 8 on C331 should have 12 volts all the time. It is fed from fuse 12 in the underhood fuse block and then fuse 1 in the fuse panel. You did say you checked fuse 1?
Customer: replied 2 years ago.
Yes, checked fuse 1. It had blown again after my initial voltage check and I replaced it again thinking I had shorted it during th first check.
Expert:  George H. replied 2 years ago.
OK, so if you have power there you should have power at the C331 and then on to the 7 pin.
Let me know what you measure
Thank you
Customer: replied 2 years ago.
I'm only getting 12 volts on the red wire. nothing on the black wire.
Expert:  George H. replied 2 years ago.
So you have a break between the C331 connector and the 7 pin?
Can you inspect them closely? There is not much distance between the two points.
Let me know what I can do to help
Thank you
Customer: replied 2 years ago.
No, I'm getting no voltage on the black wire at C331.
Expert:  George H. replied 2 years ago.
Oh, then you have a break between the fuse and that wire. Double check the fuse that you have 12 volts at both testpoints on the back then you have to trace the wire or overlay a new wire between those points.
Customer: replied 2 years ago.
Sorry, you've got me confused here. I have 12 volts on the rd/bk wire at pin 10 on C331, which looks to me on the schematic to be proper. The schematic shows the black wire on pin 8 of C331 to be ground.
Expert:  George H. replied 2 years ago.
I am sorry, you are correct, the red/black at pin 10 should have power and then you check the connector at the back where it is a black wire
Customer: replied 2 years ago.
I have 12 volts coming off the back of C331 on pin 10, but it is still a red/black wire.
Expert:  George H. replied 2 years ago.
That is fine, it runs to the circuit breaker then to C372 (shown in what I posted above to the rear of the C331. If you have power to the red/black does it make it through C372 to the 7 pin?
Customer: replied 2 years ago.
I blew another fuse. I need to get some more before proceeding.
Expert:  George H. replied 2 years ago.
Why are the fuses blowing? Are you crossing pins or is there a short in the wiring?