CLIFFS NOTES EDTION:
Is it possible to put a dual filament brakelight/turn signal bulb in backwards. If so, will weird things occur?


UNABRIDGED EDTION:
Lights on my utility trailer have been flaky lately. Assumed it was improper grounding. Still, I wanted to check all the bulbs/connections inside the bulb housings. Pulled the right rear turn signal/brake bulb just to inspect it and then put it back. Ran a dedicated ground wire to truck from the trailer. Running lights work great, brake lights work, left turn signal works. When I put the right turn signal on, the blinker indicator on the dash stays solid, I get no blinkers on the trailer or truck AND my brake controller display does weird things.

(Also, I noticed that when I turned the key off, but left the key in the on position and pumped the brakes, my dash lights turned on very faintly )

~Rob

 

When weird things happen, it usually is the ground at fault.

Are the trailer lights operated by the headlight switch??

If so, that is a big No-No.

Read here:

http://www.cummins-conversion.com/ph...topic.php?t=87

If you want your trailer lights to work as they should, then follow all this guys posts.

A lot of good information there.

 

Check your bulb socket, sounds like you got the 2 wires touching. When appling the brake its feeding back trough the running lights.

 

I see it all the time. Especially on older cars where you know they have changed the bulbs a few times. People just shovel them in the sockets and turn. If the light they are right. WRONG! lol

You can see it when they hit the brakes and one light is brighter than the other.

 

Thanks,
Y'all have confirmed my suspicions. When I go outside this morning I will check things out. Too late of a night hog hunting to be moving fast today.

~Rob

 

Turned the bulb around and everything looks good
Just really needed a dedicated ground wire run between truck and trailer.

~Rob

 

A lot of people think the trailer riding on the ball is a good ground.... NOT!!!!!!!!!!!!!!

 

I have also seen a couple times where one filament inside a bulb will break and contact the other filament. Causes some weird backfeeding.

 

I'll second the "You HAVE TO HAVE a dedicated ground between the tow vehicle and the trailer" vote.
I've seen poor grounds drive folks nuts when the turn signal circuits try to use the parking light circuit seeking a ground path.

 

If you look at the light socket, one of the tabs may be longer than the other if you use bulbs that have holding pins on the base at different hgts. That way they should go in one way, the correct way(i learned this, this weekend ) If your bulbs are diff., disregard post

 

I will have to look at the socket again. The bulbs are just regular 1157 bulbs.

Thanks,
~Rob

 

Plain-old 1157 bulbs have a high pin and a low pin; the socket has matching channels for the pins to follow.

With a plastic, or worn, socket, it is possible to get a bulb backwards.

 

Yep, 1157 thats it. If you put them in correct ( as in the pins are in the correct H/L slots) and your having brightness(sp?/word?) problems, then that means the two wires going to the light are backwards. Just cut and switch. Incorrectly installed bulbs or backwards wires will cause the light to be super bright w/headlights on and not be able to realy see turn signal w/lights on. As mentioned by bearkiller, worn/rusty sockets will enable you to put the bulb in backwards. Just take a look and youll see how they need to go in.