Instrument Illumination - secondary

[2seatcollector]

SEE SOLUTION TO PROBLEM AS CARRIED OUT AFTER THIS POST BELOW

On taking my 2002 Boxster S out after winter storage (at night), I noticed that although the main instrument functions light up bright as usual, the background or perimeter instrument lights did not. After pulling out onto the driveway the instrument lights came on, and all was well. But then I started testing them and found they don't always turn on. In fact, if they are on, and I turn the headlights on and off, the instrument perimeter lights go off. They do eventually come on, and seem to stay on once on, provided no other action is taken, such as turning the ignition on or off, or messing with the main light switch. The little perimeter light dimmer knob on the instrument cluster works perfectly, once the lights are on.

I did do a on-board computer/four-stalk hack last autumn (works perfectly, thanks to this forum and instructions), and run a trickle charger on the car - but I don't see these as being linked to the issue. I've checked all the pins on the instrument cluster plugs and sprayed them with light contact cleaner. They seem fine.

So, I'm thinking the problem is either a relay issue, or the "Light sensor for instrument illumination" (number 9 ID on page 66 of Boxster 2002 manual) which is apparently located behind a little dot on the tachometer near the redline point. I've searched the site and find no other threads on this. Can the sensor be replaced by accessing the interior of the instrument cluster (which I see seems fairly simple)? Has anyone perhaps encountered a similar issue and resolved it?

Again, the main LED instrument readings work, the yellow adjustable perimeter lights are intermittent in starting up.

Thanks again for this forum, and special thanks to Loren, who often offers wise perspectives on all things Porsche. This site has accellerated my knowledge ramp up for DYI. After years of working on Saab Sonnets (I've owned four - and still have a cherry, no-rust, 1974), and my Chrysler daily drivers, it is nice to have help for complicate and simple fixes and mods. Over all a terrific support network that makes me think I should buy a 911 Turbo, instead of the Ferrari F360 I've been considering.

2seatcollector

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OK, so after reading posts and Loren's advice below, I priced the headlight switch at $90.00. No Durametric tester in my possession, but further info from Phil at Sunset Porsche concurred with Loren, that the switch was the likely culprit.

So I removed the switch, using instructions from another post in the Forum on this site (the instructions for releasing the control knob are misleading and confusing, with the graphic showing a monster screwdriver wedged up towards the light switch control knob, when if fact all that's needed is the tip of a paper clip or jewler's screwdriver pushed directly UP, not diagonally in). I liberally applied Radio Shack contact cleaner to the center of the switch and the interior rim and worked the switch a bit. The switch is sealed, so little fluid comes out. So I put the knob mandrel inside a shop vac nozzle and let her rip, to extricate excess contact cleaner fluid. I can't imagine any dust inside the switch because of it being sealed. On re-install, the secondary dash and various control lights worked again, immediately. So, hundreds saved again by RennTech.org, Radio Shack contact cleaner, and me. I can just imagine what a dealer solution would have been - replace the switch at a minimum of $250 parts and labor. $250 I'd rather put in the piggy bank for a used 911 Turbo.

2seatcollector.

Edited May 26, 2011 by 2seatcollector

[Loren]

If you have any other headlight related anomalies I would suspect the headlight switch.

The sensor can be tested with Durametric, PST2, or PWIIS tester.

Left - Dark (sensor covered) -- Right - Light (sensor with flashlight on it)

[2seatcollector]

Thanks for the tip! I had already run through headlight switch functions, under the same suspicion you suggest. All lamps function as they should. If the instrument light ambient light sensor is the issue, can it be replaced? (I've seen on 911 and Boxster forums how expensive instrument cluster replacement can be!) - 2seatcollector