Trailer lights.

[wellcraft19]

Re: Trailer lights.

When working trailer light problems, I do the following:
1. Clean out the trailer light connector (especially if it is the smaller 4 wire connector) from crud and corrosion
2. Reset all the bulbs and verify that they work individually when placed in their sockets
3. Use a power source (battery, portable 12V supply, or other) and power up each circuit in the trailer individually
4. If not working, fix ground connectivity issues
5. Reconnect and try on vehicle (or several if the trailer is "OK" but the trailer/vehicle combo is not).

Since most modern vehicles (but probably not a 1977 Dodge...) have what is called a "trailer light converter" (due to the fact that the car likely have separate turn signals and the trailer uses the brake lights for turn signals, I've seen those "converters" fail as well. Short circuit or just plain overload due to too many lights on the trailer.

What I did (Toyota LandCruiser) was to pull a dedicated power source wire from (fused) battery directly to trailer connector in order not to overload "trailer light converter". This runs via a relay that is trigged by the 12V "tail light" feed coming out of the "trailer light converter". In case you get a short in the "tail light" circuit, not the "brake light" circuit), you are less likely to damage the vehicle's tail light wiring (+it provides me with a relatively hefty source to feed other stuff in the back of the car, all based of course on the size of the wiring installed).

 

[GA_Boater]

Re: Trailer lights.

That would probably work ok, or just double it up might be better. The reason this ground to the frame is important is the battery is grounded to the engine, but it only grounds the engine which is rubber mounted, including the transmission. The body is also rubber mounted as well. Now some mounting bolts may supply a ground path, but it isn't a good ground and it isn't always solid. I don't think it would hurt to also run a doubled 10ga. from the frame to the body also. Then all bases are covered for frame and body grounding. You truck is a '77 in Ohio so it's had 34 years of exposure to road salt. Who knows how solid the grounds are between engine, frame and body. Good luck and come on back with hopefully good news.

 

[GA_Boater]

Re: Trailer lights.

Wellcraft - This truck uses dual filament bulbs so he doesn't have a converter. And the problem is in the TV, not the trailer.

NYBo - I think he charges ok - hopefully, but he is missing grounds or has some bad grounds somewhere. If re-grounding doesn't work then it's time to start chasing volts - ugh!

 

[Jetwash]

Re: Trailer lights.

This is a description of bulbs wired in series, which is NOT the case here.They are in parallel. A long as the circuit is able to provide adequate amperage (current), the bulbs will remain at the same brightness level.

To the OP: Have you checked the charging system in the truck?

I know what series and parallel are. Im not going to make the assumption that the OP is dealing strictly with parallel circuits. I dont know who played with the wires of the truck or the trailer.

 

[N1265]

Re: Trailer lights.

The charging system on the truck checks out OK and I am running a new battery, 100 amp alt with a new volt reg. ( Had to upgrade for the plow last winter).

I checked some pictures of when I did the exhaust manifold gasket and the ground strap was never present when I started , so It may have been missing for quite some time. I think I will just start running new ground wires : bed to frame, frame to battery, cab to battery, radiator support to battery, fender to battery and new neg cable to to engine.

Also, I will run the truck side of the trailer plug ( ground wire ) to the bolt I will use for the bed to frame wire.

I have some 10 ga wire ( and maybe some 8 ga ) left over from another project that I will probably use.

Does this sound like the right plan ? should I do anything different ?

 

[Jetwash]

Re: Trailer lights.

Id guess from the battery to the body and body to the frame. The distance is short so 8 guage should show improvement if its possible. I guess if you wanted to go all the way hook up ground strap to the road. Cant predict lighting and powerlines. Thread cutter screws are probably the best bet, but I would drill out the hole old school. Allen head bolts are grade 12 and are not plated and might need a tap on the frame. Dielectric grease is your buddy.

 

[GA_Boater]

Re: Trailer lights.

The charging system on the truck checks out OK and I am running a new battery, 100 amp alt with a new volt reg. ( Had to upgrade for the plow last winter).

I checked some pictures of when I did the exhaust manifold gasket and the ground strap was never present when I started , so It may have been missing for quite some time. I think I will just start running new ground wires : bed to frame, frame to battery, cab to battery, radiator support to battery, fender to battery and new neg cable to to engine.

Also, I will run the truck side of the trailer plug ( ground wire ) to the bolt I will use for the bed to frame wire.

I have some 10 ga wire ( and maybe some 8 ga ) left over from another project that I will probably use.

Does this sound like the right plan ? should I do anything different ?

Yes. That should take care of the grounding. Just any bolt you can get to, don't need anything special or any new bolts. Important thing is bright and shiny and use some crimp lugs. on the wire ends. It will last another 34 years!

 

[N1265]

Re: Trailer lights.

Well, A buddy at work hooked me up with some #2 cable that I installed as a replacement " braided ground strap" . First I drilled a hole, wire brushed the frame and welded a 3/8ths bolt from the back side to create a stud. I decided to go from the frame to the engine at the same point where the engine ground wire attaches to the front of the left head.

( Battery -neg, to engine head, to frame )

The cable and ends are new, crimped and soldered. and covered with dialectric grease.

I ran it this way to avoid having to many connections hanging from the battery itself. The problem is that the condition still exist with the dimming lights when the turn signal is on.

My question is : is there a problem with running the ground this way, and can I put this item to rest and continue looking at other ground areas ?

 

[Grandad]

Re: Trailer lights.

My question is : is there a problem with running the ground this way, and can I put this item to rest and continue looking at other ground areas ?

I think you've certainly assured ground continuity between the negative post, the engine and the frame. I would now look at getting a solid connection between the frame and the metal body which is likely mounted via rubber and/or rusted mounts. Did you ever try putting a temporary jumper from the negative post to the tailight frames? As someone said earlier, it doesn't hurt to add more ground jumpers, but being the lazy sort I am, I like to know my mods will work before I get too much invested. - Grandad

 

[GA_Boater]

Re: Trailer lights.

Hey N1265 - You got the battery, motor and frame covered. You can run 1 more from your frame stud to the firewall and then you have the cab. If you have a pick-up and have enough wire, one more from your stud to the truck bed. If you have a Ramcharger like I do, no need for the wire to the bed.

That should take care of any ground problems. Granddad has a pretty good idea with grounding the tail light housings to test, I have my fingers crossed for you.

 

[N1265]

Re: Trailer lights.

Well, using an existing hole in the frame, I sanded around it and welded a 1/4" nut to the frame and ran a 10 ga. wire to the frame to the bed of the truck. I also mounted the ground wire for the trailer plug to this bolt.

when I did this I lost the left rear lights

after looking into the situiation, I found the wires were frayed on the pig tail to the light assembly. I figure a PO tapped into the harness with one of those line taps and allowed the wire to corode over time. After re splicing them together, soldering and shrink wrapping them I really thought I had the problem solved. The lights work again , however the condition of them dimming when the turn signal is on still exists.

Tomorrow I will look for some more frayed wiring on the back of the truck...

But for now I am wondering, Just how good of a ground will be conducted threw a weld ?

 

[12vMan]

Re: Trailer lights.

But for now I am wondering, Just how good of a ground will be conducted threw a weld ?

The weld will conduct fine. I would coat the weld as well to protect it from rusting.

 

[N1265]

Re: Trailer lights.

everything is shiny metal and coated with dielectrig grease, Should I be using something else ?

 

[12vMan]

Re: Trailer lights.

No, that's perfect!

 

[Jetwash]

Re: Trailer lights.

Too bad you dont have a test light for every terminal on the plug. You need to isolate the problem in the truck or the trailer to shorten your search. Given the condition and age of the truck, I would take a very long look at the fuse box and I would investigate whether you have wet carpet. The scenario ruined a fuse box in a truck of mine.

As reference before, you have series and parallel. But series parallel in circuits in lighting will mess up the function of those lights. I still think, a ground is contacting another power lead which essentially diverts the course of the current. Or, you have a hot lead touching another hot lead.

If all else fails, check the ohms in the various circuits. If the wires on the trailer are 18 guage, you might want to increase the guage and reduce the resistance and thus brighten the lights down stream of that resistance. I have used a testing unit that allows testing for resistance and malfunctioning diodes in addition to short to ground and short to power. It was a self contained unit used in the ford asset program. Amazing stuff.

 

[NYBo]

Re: Trailer lights.

As reference before, you have series and parallel.

No, it's all parallel. Please stop confusing the issue.

 

[N1265]

Re: Trailer lights.

Well, I spent most of the day working on the truck, First I went threw all the wiring rear of the axle and found a couple of spots that were frayed and taped. I cut out the bad spots , but spliced them together and also did away with the plugs for the tail light assemblys ( spliced them together also ) checked the bulbs and made sure the they were good and re cleaned the ground for the tail light housings.

No effect...

Then I went up front and re wired the ground wires for the headlights and turn signals straight to the battery. ( they were grounded to the radiator support )

No effect...

Then I cleaned the sockets for the front running lights and when I was checking the bulbs I noticed that one of the 1157s had a broken filament that was laying across the other filament, making them both glow when the turn signal was on.
I thought Ah Ha

But no effect...


Now I am wondering , is it acceptable to put dielectric grease in the bulb socket ?
( At the bottom where contacts are ) wouldn't it affect the current for the separate filaments ?

 

[Grandad]

Re: Trailer lights.

Now I am wondering , is it acceptable to put dielectric grease in the bulb socket ?
( At the bottom where contacts are ) wouldn't it affect the current for the separate filaments ?

The term dielectric used here is a bit of a misnomer. Dielectric grease does not provide any appreciable resistance value if a film of it was put on 12 volt spring loaded contacts such as on your 1157's. They'll still make good contact. It also won't provide a current path to short between the tail and signal circuits. - Grandad

 

[N1265]

Re: Trailer lights.

Ok, I know the last time I had them out I just took the tube and squeezed a blob of grease in the socket, then installed the bulbs...