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Blowing Headlight Fuse

M

mart1922

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[FONT=arial"]Does anyone have any ideas on this one?

[FONT=verdana,geneva"][FONT=arial"]Every time I switch my main beam on in my 944S2 it blows the fuse for passenger side dipped beam. I change the fuse and the dipped beams work. But flick on the main beam and the same happens again . I have changed the bulbs but it did not help.

Thanks.

Martin[FONT=verdana,geneva"]
 
Porsche wiring does suffer with time. My 924S has one or two non standard wiring adaptations due to failures over time.
It sounds as if too much power is getting to the fuse when the main beam is used. Have you tried removing the fuses for main beam and seeing if the fuse still blows? Does main beam still continue to work? Try using a multimeter on the fuse panel to see if there is a significant increase when switching on main beam. (You will need an assistant, one to flick the switch, one to use the meter) Does the dipped beam remain on when main beam is on. (multimeter into the bulb holder is the easiest way to check without being blinded be the lights)
Hope this helps but I'm sure someone more knowledgable will give you a better reply to your question.

Cheers,
 
Possably a broken wire where the cable flexes as the headlights go up and down, there has been a few cases of the failing there on various forums over the years.
Tony
 
Slightly hijacking the thread but thatis one of my modifications. Not sure if that would cause a fuse to blow but as I have said before I am no electrician.

Cheers,
 
Sound like an earth problem or a live wire touching an earth somewhere in the system.. headlight ,wiring, or possible switch, this in turn is blowing the fuse instantly when the main beam is switched.
 
I'm having a similar problem - except it's the RH headlight fuse that's blowing.
Originally the light wasn't working, I changed the bulb but still it didn't come on. At that point I checked the fuse...

Car is going into the shop today for new wheel bearings, am going to ask them to look at it (the light) quickly at the same time. Am conscious that electrical problems could rack up hours of labour before a problem is found though.
I'll let you know the outcome if they manage to get on top of it
 
I'd wager a reasonable wedge on relay G12 or G11. If I remember correctly (don't have diagrams to hand) G12 energises when you switch on high beam which in turn de-energises G11 to switch off the low beam (with the H4 headlamp bulb you only have one filament lit at a time). If G11 is faulty and switches the +ve to ground it will pop the fuse immediately. Just a thought....

 
I had exactly the same problem last year, and my local garage diagnosed and repaired a wiring fault. The loom was earthing to the body work(not sure where but think it was around the bulkhead area)

Charged me 2 hours labour, total bill £106 inc VAT
 
Their first guess before looking at it was that the wires/loom would be cracked due to the 'pop up' nature of them, causing it to short somewhere.
Will see tomorrow...
 
Found the fault on mine. The wires were broken near the headlight where they move up and down. As I felt down the loom I could feel the break and slit it open to find a mess of broken wires.
 
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