Help! Front marker lights out, but turn signals are working?

[rw229]

Need some help troubleshooting the front lights on an '87 US Carrera... Please bear with me

The side marker lights are out as well as the right front, but the left front works. Both front turn signals and headlights work and the rear markers/TS/brake lights also work as they should. Fuses 5, 6, 9 and 10 are good and I've cleaned the connectors in the front housings and replaced all of the bulbs.

I'm not an electrical wiz, but I did take some measurements. I'm just not sure how to interpret them.

Right TS to battery ground = 12.8v
Right marker to battery ground = 12.8v
Right TS to ground connection at the headlight = .04v
Right marker to ground connection at the headlight = 0v

Left TS to battery ground = 12.8v
Left marker battery ground = 0v
Left TS to ground connection at the headlight = .01v
Left TS to ground connection at the headlight = 0v

I've been racking my brain on this for several hours and I'm stumped. If it's a bad ground, my TS and headlights wouldn't work, Right?

[jester911]

I thought this was unique to 86 only but this may be your problem. There is a diode that controls only one side marker light. In my car it is under the dash a touch left of center of the steering column.

The part # is OEM-911-617-108-00. The thing has an opaque plastic case with a wire going into each end. You open the case and you will see the diode.

I just replaced this in mine and it worked for the first time in 2 years.