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LED light problem

Posted: Sun Mar 12, 2017 6:30 pm
by dustrat
Decided to change bulbs on my 73 12volt Ghia to LED. Single contact bulbs for flashers and reversing no problem but when I changed double contact stop and tail bulbs only stop lights work. Put old bulbs back in and every thing OK.The contact segments on LED bulbs are the same and as are offset pin fitting I've checked LED bulbs and both stop and tail segments working. Any ideas what might be problem. :?:

Re: LED light problem

Posted: Sun Mar 12, 2017 6:48 pm
by Piledriver
I'm running Sylvania Zevos on my 73 T3 (same taillight assy as late Ghia)
no issues: Bright as hell, and work with the reflectors. ... B01CKQP3XA

Your turn signal flasher may need upgraded to an electronic version, the old school versions relied on lamp current to "switch".
The LEDs draw a lot less current, and may flash very slowly if at all with an original flasher

Re: LED light problem

Posted: Mon Mar 13, 2017 8:04 am
by sideshow
Running lamps are not effected by the flasher. I would suspect a collapsed push pin in the housing if it lights on the bench OK.

Re: LED light problem

Posted: Mon Mar 13, 2017 12:03 pm
by Marc
Haven't experienced this, but here's a thought. Are you certain that the grounds are good? Specifically, the ground contact between the shell of the lamp and the bulbholder (since the signals work the bulbholder itself must have a good ground). Incandescent double-filament lamps will kinda-sorta work with a bad ground (although with interraction between bright & dim filaments) because current can find an alternate path to ground through the other filament and via the common wiring to the grounds of other bulbholders. Since LEDs only pass current in one direction, that "backfeeding" isn't possible.

Re: LED light problem

Posted: Mon Mar 13, 2017 3:21 pm
by dustrat
Thanks again for advice. First of all I have not changed the flasher unit over but will get a EP35 LED Flasher unit tomorrow. After reading more on the subject it seems that is the problem with flashers. :D Im also going to try something else with tail lights. :idea: The brass tabs on lamp that make contact with bulbs are OK and are making contact with LED bulbs. Current must be coming through as normal bulbs work. Will put another post tomorrow and let you know outcome.

Re: LED light problem

Posted: Tue Mar 14, 2017 3:40 am
by Piledriver
One of the bulbs I bought was bad first time out one of the chips was installed backwards, no current=no light.
Buying locally helps, esp if you swap them in the FLAPS parking lot. :lol:
Don't forget the dielectric grease and, clean those sockets, the pot metal sockets are far more of an issue than the brass bits.

Re: LED light problem

Posted: Tue Mar 14, 2017 1:57 pm
by Marc
di•e•lec•tric (dīˌĭ-lĕkˈtrĭk)►
A nonconductor of electricity, especially a substance with electrical conductivity of less than a millionth (10-6) of a siemens.

Dielectric grease is an INSULATOR, designed to stop the flow of electricity. Legitimate uses are to seal the rubber ends on sparkplug wires or to slather over an already-made-up connection to block moisture from getting to it and causing corrosion.
It should NEVER be used on surfaces that are supposed to be making electrical contact - for some reason in the automotive field its primary use seems to be misuse. ;)

Re: LED light problem

Posted: Sun Mar 19, 2017 5:05 pm
by Piledriver
OK, you made me look it up...

I had previously posted a long response to that, but it seems to have been digested by the board upgrade.
I'll limit it to this, it only covers "noncritical" appications like aircraft, spacecraft, and nuclear weapons.

The tragedy of Apollo 1 may not have happened if the connectors were properly filled with dielectric grease...
That was a lesson learned the absolute hardest way. (that and don't run electrical junk in pure oxygen)

The proprietary blend used below AFAICT is possibly fluorocarbon grease, although PAO oil is in there too, perhaps as an antioxidant. It may also be just a PAO oil in a teflon-powder based thickener.
(There is such a thing as fluorocarbon soap, so ...)
I assure you its absolutely a dielectric compound, none better.. ... 8&oe=utf-8
and ... 20Navy.pdf

For most of our more pedestrian uses, silicone grease works absolutely fine, as long as it is a well designed connection with a wiping and spring action. Spade connectors count as long as they are tight.
Ideal use is in a sealed connector, as it wont dry out.

Don't use it on Molex connectors.... In fact, don't use Molex connectors on anything, they suck.
The air and water-tight seal is the goal, Molex connectors have ~no wiping action, and little spring.

Also, don't use it on relays, as at least theoretically silicone oils can outgas and insulate the contacts with silicon dioxide (AKA quartz), and small signal relays usually don't have enough wiping action on the contacts to self clean.
Power relays like you would use in a car usually do, so I don't sweat it.
I don't mount relays where they can get wet as a rule.