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No left rear blinker or brake light

926 views 10 replies 4 participants last post by  Russellbgoodman 
#1 ·
I have some extras and add ons here and there but my current issue is no rear brake or blinker. I have rear LED's with the LED relay already swapped and also my switch on the steering column recently swapped also. I have checked the wiring of the led to the factory wires they seem to be connecteducated very well, what I have tried so far is unplugging the entire led and housing plugging a factory light in and no difference. Both tail lights come on but when turning left blinker on nothing happens in the rear also when brake is applied the drivers idea left rear does not increase in brightness? Please help my next step i can think is to check maybe the appropriate colored wire closers into the cab to see power is shorted out somewhere near rear of vehicle, any suggestions greatly appreciated.
 
#2 ·
I was going to say maybe your ground is bad, but if any light comes on that shouldn't be it. I'm not sure other that triple check all the connections, follow the wires as best you can to see if one is frayed, or put an old taillight in its place to see if it works then. (you could also take the other taillight off and connect it up just to see if it will work then). Hope you figure it out.
 
#3 ·
The signal/brake wire from the m-f switch to the left taillight is dark green/red.

Best to check for 12v power 1st at the m-f switch connector (pin 9) then at the taillight connector using a 12v test light. If good at the switch, the switch is good. If no good at the light there is a wiring problem between there & the switch.
 
#4 ·
The signal/brake wire from the m-f switch to the left taillight is dark green/red.

Best to check for 12v power 1st at the m-f switch connector (pin 9) then at the taillight connector using a 12v test light. If good at the switch, the switch is good. If no good at the light there is a wiring problem between there & the switch.
My m-f is fairly new but I've read some new ones are even bad if I check at pin 9 that means it's from steering wheel forward if no power, otherwise this will be from taillight plug to dash somewhere in between, I've bought and plugged in factory light and it had the same result would turn on but no flash or brake light only on the one side
 
#5 ·
You need to see where you have power in that circuit when you have the brakes on or the left signal on. It is easier to test using the brakes. And yes, start at the switch since you have made changes to the back. If you get power at pin 9 (powers the left rear) the switch is probably good. That eliminates one thing & work from there. It is just a step by step process.
 
#6 ·
You need to see where you have power in that circuit when you have the brakes on or the left signal on. It is easier to test using the brakes. And yes, start at the switch since you have made changes to the back. If you get power at pin 9 (powers the left rear) the switch is probably good. That eliminates one thing & work from there. It is just a step by step process.
So today I remove steering column and run test light while left blinker activated, this was tested but touching the back side of wiring harness where pin 9 would be located and one right below I found two places I touch that blinked making me think the switch is good let me know if I did not correctly test the switch but 2 locations had constant power and two separate locations flashed and this was while left blinker was activated. I did not physically do 12 volt test at rear plug but after testing two separate rear lights (my led one won't flash and the factory won't flash) I feel as there is a loss of signal maybe somewhere within the cab now to trace down, is this correct should I open the wires running within the cab behind drivers seat up along roll bar and search next?
 
#7 ·
To properly test for power with a test light you need to clip the end to a good ground & probe with the pointed end. I don’t think there are any grounds in that connector. You do have 2 pins for left signal & 2 pins for right since the front & back are separate because the fronts don’t have the extra function of brake lights. Pin 9 is left rear & pin 3 is right rear. Pin 10 is left front & pin 1 is right front.

If that all checks out you really should go to the back & trace from there. If you have a trailer hitch with wiring that is a common place to have problems but any exposed area is more likely to get damaged so out back should be checked first.

You have 2 pins, 5 & 6 that have fused power & 2 pins, 4 & 11 have input & output to & from the flasher so testing those are not needed.
 
#8 ·
To properly test for power with a test light you need to clip the end to a good ground & probe with the pointed end. I don’t think there are any grounds in that connector. You do have 2 pins for left signal & 2 pins for right since the front & back are separate because the fronts don’t have the extra function of brake lights. Pin 9 is left rear & pin 3 is right rear. Pin 10 is left front & pin 1 is right front.

If that all checks out you really should go to the back & trace from there. If you have a trailer hitch with wiring that is a common place to have problems but any exposed area is more likely to get damaged so out back should be checked first.

You have 2 pins, 5 & 6 that have fused power & 2 pins, 4 & 11 have input & output to & from the flasher so testing those are not needed.
So after testing the trailer light plug I have no power when left blinker indicated meaning I think next I'll have to open wire harness within the cab and look for a short, green with red I've read
 
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