Porsche 911UK Forum

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

Another minor niggle (OBC display problem with solution)

Eggman

Well-known member
Joined
30 Dec 2007
Messages
322
Hi guys,

Did a little search couldn't find anything in reference to this problem I have.

The back-lit dispay thats shows MPG, Speed etc etc on the clocks of my 993 TT has a problem. The back light was flickering for a week or so, and it has now gone completely. Not a problem in the day light but obviously an annoyance at night.

Anyone experienced the same and/or know how to fix it per chance?

Many thanks!
 
Very common problem for the OBC I'm afraid eggman.

If you're lucky it's just the bulb. More likely however is the printed circuit board develops a fault knocking out the illumination.

Alan @ Aceparts has managed to fix the problem with a bit of niffty soldering. So when you turn the lights on, the OBC is illuminated. Alternatively you'll need to replace the rev counter! £611 + VAT from your friendly stealer :eek: The price is etched on my brain from almost 3 years ago! :roll:

When the OBC works correctly it'a actually illuminated all the time.

My OBC did the same as yours and it turned out to be the circuit board :cry:

I managed to find a perfect secondhand rev counter with OBC and it's been fine for the last 2.5 years (touching wood!)
 
A gent and a scholar, will do a little investigation thank you.

Having only recently purchased the car, what with storage beforehand and and the valet on sale there was a lot of condensation in her.

Even the clocks got effected, wonder if this had anything to do with it perhaps???

Either way a course of silica "dry-boxing" and air-con en route have seen an end to that problem.
 
If it is the bulbs, you'll be surprised how much they cost. You can't get them from Halfrauds and your local friendly OPC charge the princely sum of £6.78 + VAT each. The ones that illuminate the gauge are 1.5 W and the ones for the idiot lamps are 0.9 W. I don't know what the OBC ones are but the 1.5s are yellow and the 0.9s are green. You'll need to test them with a multi-meter or a power source as you can't always tell they're blown by looking at them (either 9 or 12 V DC will do) The standard rev counter has 2 yellows and 3 greens.
 
Unfortunately its not looking like the bulbs, as the back-light came on for a bit today.

*****, will remove it for a closer inspection.
 
Sometimes my fuel gauge, does not have light, a little flick and the light comes on, i think its probably a dry solder joint in there somewhere as its now at least 10 years old. Have not had the gauge out though to see if the bulbs are just loose.
 
Hello,

I had the same problem. You will find what you are looking for on the forums.rennlist.com site.... Do a search on "OBC and transistor" in the 993 turbo and 993 forums.....basically what happens is a a transistor on the board fails and this causes the backlight issue....the issue only occurs when your headlights are on right?

You can replace the transistor with a 45p one from maplins....a lot cheaper than £611. I have attached a doc that shows what I cut and pasted from the rennlist site.

You need a decent soldering iron and fine solder.
cheers.
 

Attachments

  • obc_disp_repair_108.doc
    160 KB · Views: 39
Nice one king k.

My OBC display failed, the OBC is permanently backlit normally but mine had no light. The display was still there, but very faint. I guess the resistor was the culprit.

Cheers again for the write up.

Moving this to 993 FAQs.
 
Hm, how interesting as mine failed last week. However my display is dark and hard to see even in daylight with the headlights off whereas previously it was visible in the day. Therefore is mine the same problem? I certainly won't be removing any parts myself so I assume this should be a simple thing for my local mechanics to diagnose & repair?
 
I would be very suprised if your mechanics will take the tach out and start soldering components.... an electronics repair shop would, the people that repair televisons and hifi could repair the tach for you..
 
hi there,
i have the same problem
which is the best method for removing the rev counter?
 

New Threads

Forum statistics

Threads
124,357
Messages
1,439,492
Members
48,717
Latest member
Atlas.997
Back
Top