Trailer Lights Again

Gary from Muleshoe · Apr 19, 2011

I hooked up the ground as most everyone suggested and the problem did not go away. So just to satisfy my own mind I hooked up to my 16' car hauler and everything works great. Back to the 6' I did an ohms check across the plug I get continuity between the running lights and both signal lights. Now i know this is not right. If I take the bulbs out everything is normal.

With the bulbs in I get continuity between the turn signal and the running light directly at the light its self without the harness connected. This is on both lights. Take bulb out it goes away.

Did I get a bad set of lights? Old lights do this also. Never had one like this before.

Kentb of SWMO · Apr 19, 2011

I have found the easiest way to trouble shoot trailer lights is to us a battery charger and some jumper wire. Ground the negative side of the battery charge to the frame and use the jumper wire to connect the positive side to each terminal on the plug. You can then see what the light are doing. The grounds you really need to check out is how well the tail light sockets are grounding to the frame of the trailer.

Kent

Gary from Muleshoe · Apr 19, 2011

After the first post I went back and checked the wiring harness it is not shorted at all. This really makes me think I got some bad lights.

Anonymous-0 · Apr 19, 2011

I guess you've checked to make sure the main bulbs have been installed correctly and have not in some strange way got put in wrong? I've seen this done before is why I ask.

Gary from Muleshoe · Apr 19, 2011

Yep checked that.

Dick W. · Apr 19, 2011

Are you sure the proper bulbs are being installed? I've seen this where a single bulb is installed where a double bulb belongs.
1156/1157 or 3057/3157. HTH

Geo-TH,In · Apr 19, 2011

I had a gray moment just once! Took my lights off before I painted the trailer and then nothing worked. Ground is made through the 2 bolts that fasten the lights to the trailer. A good paint job prevented the bolts from connecting to ground. Run a ground wire to each bolt that fastens the lights to the trailer. I used a mower battery to test with. Same as using a charger as suggested.

Joe in OH · Apr 19, 2011

you will have continuity between the wires for the parking and turn light circuits. the filaments both are connected back to the ground. I tested a new 1157 bulb and got 2.6 ohms and .6 ohms between the light contacts and the body(ground). between the light contacts was 2.6 ohms. all of these readings set off the "beep" of the continuity check

Im not an electrical engineer, but i assume the .6 is the running light, and the 2.6 is the stop/turn light. more resistance=brighter

not sure if this helped.

DownSouth · Apr 19, 2011

Gary,
Hook a seperate ground wire from the frame of the trailer to the frame of the truck. Or an easy way to test it, if you have a set of jumper cables hook the same color clamp on each end, one to the trailer, other to the truck. Be VERY sure you are grounding somewhere that will work (no paint, rust etc.)
If that fails, if you have a roll of wire hook one end to the neg post of the tow vehicle battery, other end to a good ground point on the trailer.
I realize your sold on the idea that you could have bad lights, but from your latest description it still sounds like a bad ground.....or a lack of ground.

DownSouth · Apr 19, 2011

And if you get frustrated, just put a set of magnetic lights on the fenders. I have a set that I keep in the tool box in case of emergency. Why? Well I got stopped one time and was told I had a light out on my flatbed, seems like it happened now and then since it bounces pretty bad when empty. I thanked the officer for letting me know, got the lights out of the toolbox and put them on the trailer. He smiled and said have a nice day.
They are on sale at Harbor Freight for 20 bucks.

Bob M · Apr 19, 2011

Joe - You're right about the both filaments connected on the ground (the lamp base).

However the stop/turn will be LOWER resistance filament; the higher resistance is the running light. (Less resistance = more current = brighter light)

Old Roy · Apr 19, 2011

I'm with Inno On the first topic you made

---------------------------------------------------

Inno

04-18-2011 19:46:17
76.64.227.144

Re: Trailer Lights in reply to Gary from Muleshoe, 04-18-2011 18:49:09
A 6" trailer isn't long enough to ground properly, try a longer trailer. :lol:

I'm just kidding, but it probably is a grounding problem.

--------------------------------------------------LOL Seriously I did have the same problem and it turned out to be the cheap contacts inside the 20.00 set of lights I bought bending and shorting both filaments on one side. Bought a set of 40.00 LED from harbor freight and no more problems.
Untitled URL Link

unclemerle · Apr 19, 2011

Had the same problem and yes grounds checked OK. Only after I ran a seperate ground to each light did the problem go away. Merle

Offandgone · Apr 19, 2011

Gary check the bulbs to be sure the two filaments are not shorted together on one of them. Not a common problem but it has happened with new bulbs that were defective.
Frank

jim johnson · Apr 19, 2011

Gary I've had the wire inside the bulb break on one end and short across to the other but all that did was run my break light all the time. Check inside plug and make sure you don't have even one small wire shorting across, that's what it sounds like to me.

Jim

Crem · Apr 19, 2011

Joe in OH is correct that what you are seeing between the bulbs is normal if you are just checking continuity. The lights are all connected together by the ground side and you are reading through the low resistance filament from one bulb to the next one. This actually tells you that your grounds at those points are good. Maybe you are losing your ground at your plug. You could do a continuity check from your bulbs to the ground on your plug. I like to read the ohms directly rather than do the continuity thing. If you have a digital meter and are reading ohms make sure that your indicator says ohms and not K ohms or M ohms when you have the probes in place and are measuring. You may have to sharpen the probes so that they can dig in.
Those trailer lights can be a pain in the azz and it seems to happen right when you need the trailer.

huntingreen2day · Apr 19, 2011

I agree with the others that the filaments are shorted together in one of the bulbs. Seen this happen several times.

C.R. · Apr 20, 2011

friend of mine had a boat trailer was giving us fits I found one of the lightbulbs in the fixture backwards/or upsidedown and that was making it do all kinds of screwy stuff so take the bulbs out and make sure they are in the socket correctly

Bspauld · Apr 20, 2011

I had that happen to,drove me nuts trying to find the problem

Joe in OH · Apr 20, 2011

If you havent replaced the entire wire harness at this point, and you still have not found the problem, you would be wasting your time. I read you replaced the connector.

Wire harnesses for this size trailer are cheap, and replacing it now will give much more reliable service later. Also, did you replace it with a proper 4 flat connector for this size trailer, or did you go to a 7 flat/round to fit the truck?

http://www.accessconnect.com/trailer_wiring_diagram.htm

http://hitches4less.com/trailer-wiring-connector-diagrams.html

http://www.harborfreight.com/four-way-trailer-wiring-connection-kit-96658.html

http://www.harborfreight.com/12-volt-magnetic-towing-light-kit-67455.html

http://www.harborfreight.com/seven-way-rv-blade-to-4-wire-flat-adapter-67620.html

Trailer Lights Again

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Member

Well-known Member

Member

Member

Member

Well-known Member

Well-known Member

Member

Member

Well-known Member

Member

Member

Member

Member

Member

Similar threads