Hi all, looking to get an answer on an issue I have with my 68 Cutlass S parking lamps. First off the Drivers side is very bright and the pass side is normal or dimmer. When the lights are off the blinkers work on both LT and RT but when the lights are turned on the brighter drivers side will not blink. I checked and cleaned the grounds and replaced both bulbs but I am stuck

 

This is the classic bad ground problem with an 1157 bulb. The bulb has two filaments which are tied together at one end that grounds through the bulb base. The park lamp circuit and the turn signal circuit use separate filaments but share the ground. When the ground is bad, the turn signal filament grounds through the park light circuit. This lights both filaments, which is why that side looks brighter. When the park lights are on, the turn signal filament sees 12V instead of ground and that's why it doesn't flash. The problem could be corrosion between the socket and the housing, or between the housing and ground.

 

this can usually be spotted with the voltmeter or test light.

connect voltmeter black to the battery - post or terminal

use red to probe for volts at various places, with the lights under study ON of course.

red lead at radiator support lighting ground screw, meter should read zero, as that point is supposed to be tied right to the battery - terminal. Therefore, at the same voltage.

red lead at light housing, again, should be zero volts.

now move to the bulb holder itself. Again, "should be" connected to the housing, and the radiator support, to the - terminal. Therefore 0 volts.

now the base of the bulb. Should still be zero volts.

If any of these show more than 0.1-0.2 V DC with respect to battery - terminal, there is your problem. If you have say a poor connection from bulb holder to lamp housing, as happened to me recently, then you will have 0V at the housing but 12V at the bulb holder- because it is no longer "one with" the housing even though it should be, and looks like it is.

The other obvious issue is someone maybe crammed the bulb in backwards in spite of the carefully designed alignment pegs and therefore the filaments are connected wrong. Or, the wires were repaired into the wrong position.

Another good trick would be to run a wire from battery - to the base of the bulb adjacent to the glass, thereby making your own well known ground path. If this cures the problem, then the factory ground path needs to be refreshed. Find the exact failure point as set forth above, by testing each component in the path.

 

Thanks for the feed back guys, I just brought a volt meter last night so I can start going threw it. I had almost the same problem in the rear tag light the ground bulb housing was bad so my friend said solder a small wire to the side socket and run the wire too ground and it worked. So I will go threw the park lamps with the meter and maybe try the same thing, its harder to get back there with out removing the front trim housing asm. Thanks again for your help.

 

Be aware that most low-impedance voltmeters won't necessarily find a high resistance problem. You need either a high-impedance voltmeter or a test light.

I've actually had to use the small ground wire on my 62. The front park/turn housings on that car are aluminum with steel sockets. The ground path is through the swaged-in steel mounting bolts to the bumper.

Can you say "galvanic corrosion"?

It wasn't feasible to separate the different metals for cleaning, so I added the separate ground wires as an easy fix. Been working that way for five years now.

 

Got it,I will start on this tonight and will see how it goes.