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foglight trouble shooting

2039 Views 12 Replies 3 Participants Last post by  siguy2k
Ive been searching quite a bit and havent been able to locate any info on the testing procedure for the fogs. Ive looked thru the online manual links i have as well. Both bulbs good. All other lights work. Fogs will not. I was going to check for voltage at bulb but didnt get to it today but if there isnt any, which im sure theres not, then i couldnt follow the wiring far enough. Help is appreciated. Also im confused on euro and us headlights. I thought the euro were h4 bulbs. Ive got clear corners and 9004 headlight bulbs with the clear fog lens. Headlights say bosch and dot. Which lights do i have? Thanks in advance.
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US pre-facelift headlights have a rectangular glass lensed headligtht surrounded by a plastic frame, which includes the fog lamp portion. the foglamps use H3 bulbs.

you pull the headlight switch straight out one click in either the parking light or normal on position to turn on the fog lamps.

page 61 of this PDF (page labeled 124) shows the fog and head lamp circuits for 1986-1990
(give the link sufficient time to load and it should take you to page 61).

the circuit looks quite simple. if the fog lamp switch is on, the grey/green wire that is on pin "N" of the headlight switch assembly is powered. this connects to pin 5 of the bulb out sensor unit, which in turn powers pins 6 and 8 for the left and right fog lamps. It appears the fog lamps are unfused on these models.
the lamp failure module is in the main relay panel behind the fuse panel under the hood, its the long(!) module "K" on the car's left, designated N7 on the schematics.

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