Porsche Enthusiasts Club Forum

first time out in the dark in my 944 yesterday coming back from the North London meeting, every time I put the indicators on, the lights went out - scary - any clues out there what the problem might be.

Thanks

Mike

Hi,

Sounds like a bit of a bad earth somewhere.

Regards,

Ben

Two earths adjacent to the headlights are the main termination here. Give them a good clean.

thanks, I'll have a look around this weekend

It could also be a short in the wiring that leads into the back of the headlamp. The wiring flexes because they pop up and down and quite often will split the insulation and cause all sorts of lighting issues.

Where exactly please Jim? Also, is there an individual earth for each side? The reason that I ask is that Im only getting dim dip in both bulp elements on the offside lamp only.

Dip Dip is a major PITA! Not sure how Porsche do it but most use a resistor in the headlight dip bulb circuit, switched by a relay. What normally happen is the resistor goes open circuit & hey presto no dd but you'll have dipped headlights. Just got in I'll go find the manual when I finish a drink & look it up, although manual very vague on UK only bits like this.
Pretty sure when you lift the bonnet there is an earth point on the bracket that supports the headlight lift mech. Again I'll look in a short while.

Any progress Mike?

I've just remembered I had an almost identical problem a few years ago and it was the contacts on the indicator stalk itself. A new S/H indicator stalk fixed it immediately

Right just had a look there are two earth points for most of the headlight circuits MPIV & MPV these are on the chassis rails the N/S one is easier to see. Look immediately under the N/S headlight linkage & bolted to the outside of the chassis rail is a bolt with around 4-5 wires on it. There is another point on the other chassis rail, partially hidden by the headlight motor & below the coil.

The dim dim module has two outputs but despite combing the electrical manual which is a full lever arch file I cannot find any other ref. to it

Thanks Jim. To recap in case Ive been less than clear. The dipped and main beam stopped working on my offside headlamp, it only shows a dimmed dip. I removed both lamps and checked the bulbs, which are both fine. When dipped headlamps are selected via the switch the near side bulb shows one fully illuminated filament and one dimmed dip. The offside bulb shows, for ant of a better description, a dimmed dip in both filaments: this pattern continues when main beam is selected too. It may be a b*stard coincidence, or it may be connected; but the side lamps (951-type lamps even though its a series one car, with wiring as standard as possible) stopped working at about the same time too... The rear lamps and everything else associated with the lighting circuits appear to operate correctly.

Simon

Deffo earth problem on the head lights. Unless the light switch or as Paul says the stalk is knackered but neither of these would give weak lighting on both filaments.
Strip bulb out of housing, make sure bulb can't burn you or paint & switch on. Find the 0 Volt line which will be earth (should be here http://www.audi-quattro.org/tech/h4bulbwiring.html) & using a bit of spare wire earth this point to a good earth. If bulb lights bright you have an earth problem, it will be the ones MPIV & V as before. If not then you have a feed problem, check the relevant fuses & make sure they are clean. A meter can help here but you need a bulb connected to load it enough.

Appreciated. I have a multimeter, but Im not particularly experienced/able. I believe that the lugs on an H4 bulb (viewed from behind) are: left vertical - earth; across the top - dipped beam; right vertical - main beam. I believe that Id use a resistance setting to test the integrity of the earths; but does anyone know what sort of reading I shoud expect?

OK Bulb connections are

Rear of bulb

+-------+
+ Dip +
| E M |
| a a |
| r i |
+ th n +

Use meter on 12V range & find a good earth such as the engine block, connect the negative (black) lead to this.
Remove bulb & lay it on something that won't burn. Switch dipped lights on, if you connect the positive lead (red) to the dip connector on the bulb you should see around 12.5 volts or more. I suspect you won't, do the same on the main, check volts (should be zero).
Now put the Pos lead on the earth point on the bulb. You may need to step the range down to something smaller than 12V say 2 or 5V. The reading if you have a good earth should be 0Volts or damn close. I bet my life it won't be. Check back along this wire & either it is broken where it bends as the light pivots or the earth point on the chassis rail is knackered.

PS I was going to do a 30 minutes 944 buying guide at Gaydon, wondering whether basic auto electrics might be a good idea! I was trained to do this so it is second nature.

Thanks Jim.. Im struggling with the quoted diagram above though. Hold on! It looks different after the forum software has re-formated the text: it confirms the pin out pattern that Ive been assuming, doesnt it?

Im still surprised that Im not going to be checking the integrity of the earths by measuring their resistance in ohms though... Maybe a car electrics 'how to' would be beneficial.

Is it because Id need a very expensive multimeter in order to read a sufficiently small resistance?