11-28-2010, 12:42 PM
I thought I'd share this because if it happened to my car in New Mexico, it will probably happen to others in more humid climates.
My wife noticed that both left parking lights were out. I was confident that it was a fuse, since there is one for each side, but they both tested fine. I then checked the bulbs and saw that 1157 bulbs had been put in place of the proper 7528 bulbs in the parking lights in the front. I thought that was clearly the problem, but then I learned that 1157 and 7528 are the same thing except one is brass and one is silver (zinc?). They have a slightly different contact, but are interchangeable. That was not it. I then verified the rear bulbs were all correct and functioning - no issue there.
I pulled out the wiring diagrams and found that the left and right sides of the parking lights can be turned on by either the turn indicator or the rotatory headlight switch. Both elements of the bulb functioned properly with the turn indicator, so that was not it.
When I turned on the headlight switch to either parking or to raise the headlights, only the right side parking lights would come on. Everything else (liscence plate light, fog lights, headlights, right side parking light) worked correctly. This exonerated the wiring above the point at which the turn indicator and headlight switch come together. The headlight switch has both a left and right side terminal for some reason. I felt it had to be the headlight switch.
I pulled the headlight switch and sure enough there was a fine, white oxidation on the terminals. I verified the switch was good and shot it with contact cleaner. The lights are back to normal. The oxidation was enough to interrupt the circuit.
The part that surprised me was that there is no higher, drier place in the car than that headlight switch, but it still formed corrosion. The switches cost $80 to replace, but I'll see how long the cleaned contacts last for now.
My wife noticed that both left parking lights were out. I was confident that it was a fuse, since there is one for each side, but they both tested fine. I then checked the bulbs and saw that 1157 bulbs had been put in place of the proper 7528 bulbs in the parking lights in the front. I thought that was clearly the problem, but then I learned that 1157 and 7528 are the same thing except one is brass and one is silver (zinc?). They have a slightly different contact, but are interchangeable. That was not it. I then verified the rear bulbs were all correct and functioning - no issue there.
I pulled out the wiring diagrams and found that the left and right sides of the parking lights can be turned on by either the turn indicator or the rotatory headlight switch. Both elements of the bulb functioned properly with the turn indicator, so that was not it.
When I turned on the headlight switch to either parking or to raise the headlights, only the right side parking lights would come on. Everything else (liscence plate light, fog lights, headlights, right side parking light) worked correctly. This exonerated the wiring above the point at which the turn indicator and headlight switch come together. The headlight switch has both a left and right side terminal for some reason. I felt it had to be the headlight switch.
I pulled the headlight switch and sure enough there was a fine, white oxidation on the terminals. I verified the switch was good and shot it with contact cleaner. The lights are back to normal. The oxidation was enough to interrupt the circuit.
The part that surprised me was that there is no higher, drier place in the car than that headlight switch, but it still formed corrosion. The switches cost $80 to replace, but I'll see how long the cleaned contacts last for now.
