syoo8

Strange thing happened tonight. Drove home normally, headlamps functioning normally. Parked the car in the garage, left the lights on, turned off the engine, then turned the lights off. (I wanted to check the headlamp filaments to see what part number to get.)

When I turned the car on again to check the headlamps, they wouldn't light. When I checked the filaments, both of them were burned.

Can anyone figure out what happened here? How could I have burned both headlamp sockets at the same time? Where did I short out the connections?

928mac

Hmmm that is strang. ILL need to think about that.

Normally I would say they were loose.

Brad

Imo000

If the bulbs are are stronger tan the stock rating, this can happen. What is the Wattage on you bulbs?

heinrich

Just saw this. If they BOTH did this at the very same time, then I would say there is a common problem. Particularly if the lights have been working well for many years, and suddenly this happened to BOTH.

This cannot happen if fuses are correct, because long before this point, the fuse would have burnt out.

Something else is wrong. Personally I tend to agree that a loose or weak / corroded connection would seem to be the most likely ... however, anywhere in the system.

borland

The weather seals likely the source of your problem. That allowed water/moisture to contaminate the contacts and allow corrosion and increased contact resistance.

The increased contact resistance caused them to heat up and melt the plastic connector.

Alan

This can certainly happen with the correct fuse. This is caused by connection issues - corrosion/oxidation, dirt, heat, dielectric grease! or damage to the terminal. Once this starts - current goes down as heat goes up - a fuse isn't going to blow under these conditions - a common misunderstanding.

This is causes by corrosion (or whatever) EXACTLY HERE right at the socket

It can we worsened by higher wattage bulbs, but has been seen with stock bulbs too. The H5 plug/sockets have very small contact areas compared to H4 so are much more susceptible to this... Why both at the same exact time - ??? - just coincidence...???

Replace the sockets/bulbs (stock watts) & ensure everything goes back together dry and free of any "special stuff".

Alan

heinrich

Can't ask for a greater 928 electrics expert here than Alan

77tony

Alan, RU suggesting not to use dielectric grease in the headlight (and tail light) sockets? TIA. 77Tony

Alan

I wouldn't - understand that its an insulator - it does nothing to promote connectivity - its only possible benefit is to seal out moisture from the connections - but these sockets are supposed to do that anyway. Pure contact "protectants" should ideally be used on accessible connections after they have been mated.

There are substances you can use that promote better connectivity by pocesses of cleaning the contact surfaces of oxidation and protecting them without compromising their connectivity - these are usually quite a lot more expensive. In this instance I'd say they shouldn't really be needed on new clean bulbs/sockets.

Alan

77tony

Just did the tail light upgrade with 6 parking/brake light LED's and do have 4 new sockets. Thank you for that info. T