The Pontiac didn't pass State inspection - right front turn signal wasn't operational. How hard can this be? I replaced the bulb while the tech continued the inspection. Still didn't work. Off to home I go....

I pulled the socket out and tested for 12V. Nothing in the socket, nothing in the wire leading to the socket. (BTW, 12V for the side marker light was present, just not for the turn indicator).

Send in the Gremlins. My wife noticed the left headlight was dim. So tonight I started playing with lights while I sat behind a Van at a stoplight.

Turn headlights on, low beam, both lights look normal. Turn on highbeams - right side headlight acts normal (high beam on), left side goes dim (lets call it half the brightness). Turn off highbeams, right side again acts normal (low beam on), left side looks the same as when the high beams were on (the same half-brightness). Turn on high beams, right side goes to high beam, no change and half-brightness on the left.

Turn the head lights off completely, then back on. Low beams on both sides look normal. Turn on high beams and the same right-side-works-left-side-half-brightness thing happens. Turn head lights off, then on - low beams normal, turn on high beams.......

I'm still behind the Van, the right front turn signal is WORKING!!! and the left side blinks slowly, at about half the rate of the right side, and has a slight delay before the blinking begins. On the drive home, the left side turn signals quit working all together (judging by the reaction of the car following me and the dash signal light staying solidly lit).

At first I was thinking Turn Signal Switch, but now I'm not so sure. It's been too long and many brain cells lost to senility since I had to really read a schematic. Any suggetions on where to begin troubleshooting? Looks like all the lighting is directed through the DRL module, should I be suspecting it is going bad? Maybe the turn signal switch? I'm thinking Module, or even relay, since the headlight trouble seems to reset once power is removed, but would a relay explain the intermittant turn signals?

It sounds like the headlight is bad, at the least. When the high beams go on an element in the low beams goes off, thats why you see the half light on the one side. So if it is a 4 headlight system the highbeam bulb is out and the low may be on the way. If it is a 2 bulb system then just change the bulb.

I had a brake light bulb short across the running light portion of the bulb once. When I had the lights on all of the brake lights were on. When I stepped on the brakes the running lights would go on. Try figuring that out! It sounds like you should check all your bulbs just so you don't go crazy.

As for the turn signals, I've run across a few different types. When a bulb goes out a few different things can happen. Either the turn signal stays on all the time (thirdgen style), they blink very fast (ford I think), or they blink very slowly (heard this one, not sure what brand.)

It sounds like you have a long night of checking bulbs, to start off with anyway.

Sorry, I forgot to add: the bulbs are good. I replaced both headlights and the brake/signal bulbs. Same problems before and after the new bulbs....

Bulbs were my first thought but after seeing how the low beams reset after turning off/turning back on, I started to think it may be something else?

How does the turn signal switch "feel"? If it's clicking up and down like it should, the problem is probably downstream of the steering column. Ever see smoke come out of the column?

Switch feels normal.

Problem is getting really crazy. This morning the headlight problem was reversed - left looked normal, right messed up. This afternoon when I left work, both right and left headlights worked normally

Left turn signal worked as above when I left work, stopped working halfway home.


This thing is really puzzling me.....

Whenever I've had strange electrical problems it was a bad ground. I'd check the grounds. First check the grounds under the dash.

Tony

In almost all cases like this "I" have seen it ends up being the multi-function switch (turn signal lever) being the problem

Check to see if you have the same electrical problems with the brakes firmly pressed as you do without them pressed. I had something similar and it turned out the wiring harness passes behind the brake booster. The pressure of the break boosters flexes the fire wall just enough over time to short the wires.