I bought new led lamps for my tail/stop light but they only work on the brake light side. Regular bulbs are ok. Battery static voltage is 12.8v but the voltage at the bulb socket is only 10.8. Is there a dropping resistor in the circuit somewhere? The voltage is the same on both terminals and the brake light side is really bright, but nothing on the tail light side. Any thoughts??

 

Have you tried it with the engine running and put a few revs through it?????

 

Hi Fred. I just replaced my lites also with LEDs. Didn't have the same issue. Direct swap and works good. I found some 1157/1156 (not sure which is3 terminal ) 3watt LEDS online. Amazing difference. Last time I looked at the schematic, didn't recall seeing anything but a direct feed. Perhaps pinched wires?
Corrosion? Just trying for the obvious. At first when you described no taillights, i thought may be the wrong bulb? but when you said regular (incandescent) bulbs work, mmakes me think otherwise. Hate to think this, but are the LEDs of good quality? Can you check their operation on the bench or even better on another vehicle?
3 Watt Luxeon LED 15mm Bayonet Based LED Bulbs at superbrightleds.com is where I got mine. Not cheap, but IMHO very much worth it. Also did the fronts too. Amazing difference. Let me know how it goes. If you need a wiring Diagram, I have on a PDF for a 93-96 'Cane.
Good luck.
Art

 

Thanks for the reply, I checked the voltage today (more time to tinker) and the batt. voltage was 12.5 static but only 10.5 @ the tail lights! So I checked the fuse buss and it too was only 10.5! So I went to the starter relay/main fuse and found corrosion and burnt ends. I cleaned this up completely and replaced wire ends, now I have batt. voltage at the tail lights but still LEDs no op on tail but OK on brake! With the engine on and @ 3k plus 14.volts plus but still no tail light LEDs lit! I bench tested the LEDs and they light right up! WTF is going on here??? Grounds are redone, star washered ect. The standard bulbs are nice and bright (seem normal). the LEDs were made by Power Products 1157 equiv. I am sort of stumped at this point...................Fred

 

Sounds weird, buy your know standard LED are current devices
Do some more testing looking at both Volts are Amps

 

Im wondering if the LEDs have a good contact in the base. I noticed on mine that the Solder terminal/contact was slightly different shaped more oval/elongated than a round bump. Check the socket again for contact and also maybe debris/crud?? Goold luck.

 

Did you check the battery at the pos neg terminals? Or from the pos terminal to another ground?
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Are the LED bulbs drop-in-place bulbs, a complete replacement to the stock bulb? If so, they might differ slightly mechanically in some way, e.g.the plus terminal doesn't come in contact with the socket terminal and similar problems.