OT-Trailer electrical problem

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Model T Ford Forum: Forum 2012: OT-Trailer electrical problem
Top of pagePrevious messageNext messageBottom of page Link to this message  By mike_black on Sunday, June 10, 2012 - 11:16 am:

When I hooked my trailer to the motorhome in SC, everything worked fine except no right side brake light. Really strange because the running light worked and the turn signal worked. the turn signal uses the same filament as the brake light. I assumed "bad ground" that would heal itself, so, I headed for ARK. I checked my lights in TN and it was the same thing. I pulled into WalMart near my destination and noticed I had no marker lights or taillights on the MH or trlr. 30A markerlight fuse was replaced and marker lights worked on the MH but not the trlr. MH taillights were a dull glow-none on the trlr ,but, the taillight fuse was OK. Marker fuse blew within a mile. Unplugged trailer, replaced the markerlight fuse and all markers worked and the tail light was as bright as it should be. The problem has got to be in the trailer. Any ideas? I'm thinking of starting by replacing the trlr plug. I've got volt/ohm meters with me as well as a test light, but, what do I start looking for and how?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Sunday, June 10, 2012 - 11:30 am:

Mike:

Check to see if your MH has a totally separate brake light set up that is independent of the turn signals. Ranger Ford pickups are like this. When using those type of tow vehicles you need a "logic box" converter to connect up a typical trailer. Hope this helps.

John


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rick Lawson Texas on Sunday, June 10, 2012 - 01:02 pm:

You have a short. I usually replace the entire light ( 10 bucks here).


Top of pagePrevious messageNext messageBottom of page Link to this message  By mike_black on Sunday, June 10, 2012 - 01:48 pm:

I've pulled this trailer with this motorhome for 6 years and it's always worked before. The female plug on the trailer is made to about 6 ft of wire that goes to a box with small battery for brakes. I put continuity meter into each hole of the plug and tried to determine which color wire went to which hole. What I found was--looking at the female plug on the trailer, the 1st and 2nd holes go to blue or green and there's continuity between any 2 of the 4 points. I don't know what the blue and green wires go to yet, but, that don't seem normal to me.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris from Long Beach & Big Bear on Sunday, June 10, 2012 - 01:50 pm:

some inexpensive covered trailers ground their lamps with self tapping metal screws that must carry the current back to ground through the rivets in the skin to the steel frame. The aluminum and steel get corrosion and the contacts fail. They simply do not want to buy another string of wire and save about $15 to $25 per trailer and mess up the customers. I had to put in return wires for our Haulmark trailer when it got to be seven years old. Nasty job because they hide the wires under riveted skin.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Harrison,Norco Ca on Sunday, June 10, 2012 - 03:26 pm:

Not an expert by any means but isn't a blue wire usually from the brake controller to the trailer brakes and green is clearance lights and tail lights.


Top of pagePrevious messageNext messageBottom of page Link to this message  By A. J. "Art" Bell on Sunday, June 10, 2012 - 04:27 pm:

I would not initially worry about the color coding on the wires.
If it worked before and nothing was changed on either tow vehicle
or trailer, it should still work regardless, even if it is a “one off”
hook-up. (A great many trailers are wired to work, not to code)
Put a good ground between the vehicle and the trailer, (like a booster
cable) for a temporary test. Did this cure the problem?
No? – Leave that ground in place and take a long piece of wire and
attach one end to a good firm ground on the trailer frame, and use the
other end to test ground each of the trailer light shells (or ground screw
if the light is plastic) in turn to see if any of them have a faulty ground.
Remember, the light that’s acting up may not be the problem, but only
the result of one of the other lights grounding back through it’s filament.
How many times have you followed a vehicle that may be signalling
and both rear lights respond, either one that should stay lit goes out
or dims etc in sequence with the other light. “BAD GROUND” !!

Regards
Art


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hap Tucker on Sunday, June 10, 2012 - 07:44 pm:

Mike,

When I've been on a trip and had a similar issue, I have gone to u-haul where I purchased a set of their "Temp" tow lights that are designed to be put on the car being towed behind one of their trucks on the tow dolly. It comes with a ground wire to each light. They used to have one designed for the trunk lid to close on the bracket and hold them to the car. I just looked and only saw the ones with the magnetic base which may or may not help you. Then I will trouble shoot the problem when I have more time -- and it is usually a ground problem but occasionally an intermittent short.

They may have a similar item at Walmart or AutoZone etc. for less. See: http://www.uhaul.com/MovingSupplies/Wiring-lights/Trailer-wiring-lights/Magnetic -Tow-A-Lites?id=2849

Respectfully submitted,

Hap l9l5 cut off


Top of pagePrevious messageNext messageBottom of page Link to this message  By mike_black on Monday, June 11, 2012 - 09:42 am:

The running light wire seems to be shorted to the frame. I guess it's like Frank's and it took 7 years to wear through the wire insulation! When it's time to go home, I'll travel during daylight hours. With the running light wire disconnected, I've got brake and turn signals. I can live with that. Thanks to all for the ideas.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Monday, June 11, 2012 - 09:50 am:

Sounds like a grounding problem. Do you have a ground wire in your harness that goes to the tow vehicle? If not you're grounding through the ball hitch. This can come and go. Usually as the parts age it tends to get spotty. With no ground and all the lights on current will flow where it can causing weird problems. Every thing worked then something changed and you didn't do anything to the system to cause it. Check your ground.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Greg Kuhnash Southeastern Ohio on Monday, June 11, 2012 - 10:02 am:

Also check the socket. I have found trouble with corrosion between bulb and socket barrel.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, June 11, 2012 - 10:39 am:


Most trailer light problems involve ground. I got fed up with fighting intermittent running lights, tail lights, and signals, so I attached a separate ground wire directly to the trailer frame with a small vise grip that clamps on the tow vehicle. Problem solved.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Doug Money - Braidwood, IL on Monday, June 11, 2012 - 03:00 pm:

Keep in mind that most new trucks have separate fuses for each turn signal and brake light R and L on the trailer. Check the owners manual of the MH and look through the fuse section and you will see, each trailer filament is protected by a fuse.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Hatch on Monday, June 11, 2012 - 03:22 pm:

Also check the MH trailer plug wiring. All the problems I ever had with them was because of the way the factory wired them. They do not have Tom Edison working there. Check the ground wire from the MH plug to the Mn ground. Dan


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Tuesday, June 12, 2012 - 05:01 am:

I don't know much about wiring, but I learned MANY years ago, a bad ground will drive you nuts, as has been said here. Dave


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