NEED HELP with truck-related trailer light/brake issues any help appreciated

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samtoddlee

samtoddlee

10 Year
Joined
Jan 25, 2013
Threads
31
Messages
1,329
Location
NW Valley Phoenix Arizona
CSC Members as they say in Star Wars, you might be my only hope.

I've been wrestling with issues on my 2002 F-250 Super Duty for the last 6-8months. I know, I know, the problem is it's a Ford. Anyways, I've been towing with this truck for years with zero issues. Until about 9mo or so ago when I noticed that my left rear blinker and brake light were not working correctly on the trailer. I pull three different trailers and issue is constant across all three. All works perfect on the truck. Originally diagnosed by B&M Bumper or one of those as a fuse issue. Up until recently, the rear lefts just didn't work at all, now it's an intermittent thing. I also recently picked up a new small camper trailer which has same issue PLUS the trailer brakes don't work or are not recognized by my brake controller. I know that trailer has good brakes as I pulled it with the seller's rig before buying.

In addition to B&M mentioned above, I also took it to Ford here in the NW valley. They had it for two days and could not locate any short or fault in the wiring that would cause the issue. Thanks for that Ford.

I know that lots of you guys pull trailers either campers or overland trailers or just pull your 4x4 rigs to the trail, so my neighbor another CSC member suggested I post it up and see if you guys can recommend a specialist place / guy / genie / guru who can help me get this sorted out. Any advice or recommendations appreciated. Thanks.
 
and thanks in advance
 
If the issue happens across all trailers and the vehicle lights are fine the only place the issue could be is either the socket or the connectors to the truck wiring right behind the bumper.
 
I agree with Ron, get out a volt meter and start testing the leads in the trucks trailer wiring socket. Also, not sure if it was factory tow wire harness or an aftermarket install by someone that may have used t splice connectors like those below. I have seen those fail more than I care to count. If they are what is connecting your trucks trailer socket to the factory light wiring harness I would be suspicious of them.
Also, me agreeing with Ron should in no way be seen as a knock on Ron. He knows what he is talking about and I am a hack when it comes to electronics.:hillbilly:

splice connectors.webp
 
Dimples said:
If the issue happens across all trailers and the vehicle lights are fine the only place the issue could be is either the socket or the connectors to the truck wiring right behind the bumper.
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This^^^^

Funner said:
I agree with Ron, get out a volt meter and start testing the leads in the trucks trailer wiring socket. Also, not sure if it was factory tow wire harness or an aftermarket install by someone that may have used t splice connectors like those below. I have seen those fail more than I care to count. If they are what is connecting your trucks trailer socket to the factory light wiring harness I would be suspicious of them.
Also, me agreeing with Ron should in no way be seen as a knock on Ron. He knows what he is talking about and I am a hack when it comes to electronics.:hillbilly:

View attachment 1353607
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And because it's intermittent, ^^^^
 
Thanks fellas I'll keep you posted. Tried to get Ford to replace whole harness but they wouldn't as they couldn't recreate problem. I think they just didn't wanna mess with it.
 
90 % of my trailer wiring problems have been the ground connections between the rig and tbe trailer or the light's negative connection.

Try running a temporary wire from your battery negative to your trailer light.

A few of my trailers used the ball to transfer the ground and had intermittant problems. Almost all of the lights only had one wire for the positive and depended on the xxrappy frame for the negative.
 
samtoddlee said:
CSC Members as they say in Star Wars, you might be my only hope.

I've been wrestling with issues on my 2002 F-250 Super Duty for the last 6-8months. I know, I know, the problem is it's a Ford. Anyways, I've been towing with this truck for years with zero issues. Until about 9mo or so ago when I noticed that my left rear blinker and brake light were not working correctly on the trailer. I pull three different trailers and issue is constant across all three. All works perfect on the truck. Originally diagnosed by B&M Bumper or one of those as a fuse issue. Up until recently, the rear lefts just didn't work at all, now it's an intermittent thing. I also recently picked up a new small camper trailer which has same issue PLUS the trailer brakes don't work or are not recognized by my brake controller. I know that trailer has good brakes as I pulled it with the seller's rig before buying.
t
In addition to B&M mentioned above, I also took it to Ford here in the NW valley. They had it for two days and could not locate any short or fault in the wiring that would cause the issue. Thanks for that Ford.

I know that lots of you guys pull trailers either campers or overland trailers or just pull your 4x4 rigs to the trail, so my neighbor another CSC member suggested I post it up and see if you guys can recommend a specialist place / guy / genie / guru who can help me get this sorted out. Any advice or recommendations appreciated. Thanks.
Click to expand...
We had a similar issue on my daughter's new-to-her 2002 F350 earlier this year. No left blinker or brake lights. Not to state the obvious, but did you check the fuse? There is a dedicated fuse for the trailer brake/turn signals, at least on the F350, and I think it should be the same for the 250? It's fuse 6, 20A fuse. In her case, it was blown, we replaced it and it was good. Until the next day. Turns out, every time the headlights were turned on, it would immediately pop the fuse. We then had to bust out the voltmeter and start tracing. Turns out the PO had done a hack-job on the trailer harness, splicing in a gooseneck harness starting at the 7-pin, and running back up to the wheel well in the bed. The bed metal had worn through the wire insulation, causing a short in the circuit. We cut out the gooseneck harness and all is good.

So, if your problem just started, first, check the fuse, then you gotta start at the plug and work back checking for continuity and lack thereof, as the case should be...
20161120_121957.webp
 
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Thanks so much guys for all the suggestions.
 
Update
Took it to another bumper /hitch specialist shop here on west side of the valley. SAME RESULT all tested well and could not locate a bypass or short. No signs of meddling with factory tow harness. Next I'll borrow a buddy's truck and hook it up to all three trailers to see if works correctly or not. If so then I'll install a brand new aftermarket harness and brake controller that bypasses the factory harness all the way from the battery to bumper. Leaving factory harness in place as don't want to short computer or any other electronic system. Sound reasonable???
 
WELL ... THE SAGA CONTINUES. My good buddy and neighbor Norm (Aeronautical Engineer, read as "wwwwaaaayyyy smarter than me" helped me test the trailer lights again last night. Borrowed a different pickup from another friend and hooked it up. Same results. Intermittent left brake light and turn signal. Used a test light to test the plug on the truck all good. Opened up the light fixture on left rear of trailer and tested the connections there all good. it'd come on and work right, then we'd tap it and it'd stop working. At one point, we blew the main trailer lights fuse on the truck. Easy ten minutes with the owners manual to locate the right 15amp fuse. Later, we would get the test light to blink with turn signals on even though no blinking at the bulb. Seems to be a grounding issue back there at that light fixture.
Does anyone know the answer to these questions: Is the rear left the "last" place to get power and ground in the trailer lights system?
And secondly, has anyone gone to LED bulbs which should require less power through the system and possibly less ground?
 
samtoddlee said:
WELL ... THE SAGA CONTINUES. My good buddy and neighbor Norm (Aeronautical Engineer, read as "wwwwaaaayyyy smarter than me" helped me test the trailer lights again last night. Borrowed a different pickup from another friend and hooked it up. Same results. Intermittent left brake light and turn signal. Used a test light to test the plug on the truck all good. Opened up the light fixture on left rear of trailer and tested the connections there all good. it'd come on and work right, then we'd tap it and it'd stop working. At one point, we blew the main trailer lights fuse on the truck. Easy ten minutes with the owners manual to locate the right 15amp fuse. Later, we would get the test light to blink with turn signals on even though no blinking at the bulb. Seems to be a grounding issue back there at that light fixture.
Does anyone know the answer to these questions: Is the rear left the "last" place to get power and ground in the trailer lights system?
And secondly, has anyone gone to LED bulbs which should require less power through the system and possibly less ground?
Click to expand...

You initially said you tow three different trailers and all of them have the same light failures. Now a second vehicle is connected and the same failures exist? When I read there were three trailers all having issues with the same tow vehicle, I concluded it was likely the tow vehicle. If it is really about a single trailer then I would suspect a ground at the fixture or connection in the bulb socket.
 
Yes you are correct tow three trailers and all three have same issue. I was shocked and dismayed when the second truck that I borrowed from a friend showed same results. Again, thinking that this fixture is the last along the line to get power and that's why same on three camper trailers.
 
At this point I would start looking at the mechanical connection between the plug and the socket. The electricity is there but it seems like the plugs may being damaged by the socket.
 
OK, so at least one of my three trailers I now have working correctly. Turned out to be a bad ground on the trailer. At least according to my RV mechanic who I know and trust.
I also switched to LED bulbs which are far brighter anyway. I'll put in another update once I get time to test the other two trailers. I still can't believe the problem was common to all three trailers.
 
samtoddlee said:
OK, so at least one of my three trailers I now have working correctly. Turned out to be a bad ground on the trailer. At least according to my RV mechanic who I know and trust.
I also switched to LED bulbs which are far brighter anyway. I'll put in another update once I get time to test the other two trailers. I still can't believe the problem was common to all three trailers.
Click to expand...

Be a believer, most of the lights that come factory on today's trailers are junk when it comes to bulb sockets and grounding. LED is the way to go. Tractor Supply even has an inexpensive set;
(go overboard on ground connections)
Blazer LED Submersible Square Trailer Light Kit for Trailers Under 80 in. Wide, Pack of 2 - For Life Out Here
 
Thanks for the link bud!
 
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