Hi All,

my speedo has stated operating intermitantly.

I have had the gearbox connection checked and it was fine. When I hit 80kph the warning light will flash, I assume to warn the tail is not up, but then the speedo will immediately start working, tail will come up etc.

Once the car has been parked for a while the speedo will stop working again.

Any ideas?

cheers

Neil

PS it is back in the shop next week but it would be nice to point he mechanic in the right direction to save some money

 

Dear Neil,
Which model 964 do you have. Which model year. Is it manual or tiptronic.
The rear wing is activated by the PDAS/ABS control unit on the C4 and the ABS control unit on the C2s. Depending upon model the speedo input is different. You say you have a sensor on the gearbox which suggests a 1989 or 1990 model.
The spoiler warn light is activated by the speed or pulse sensor and microswitch position of the rear spoiler. The light flashing like it is tells me that your speedo input is okay but the output from the speedo head is lost. This suggests the speedo is failing. Watch the odometer. Is this moving, rolling over whilst the speedo pointer remains at zero. If the odometer is working this confirms a failure of the speedo pointer drive. Not an uncommon problem especially in cooler climes. Mine does this sometimes and a light technical tap to the glass fixes the problem,
Ciao,
Adrian
911C4

 

Hi Adrian,

I have a 1990 C4 (L model from memory).

The odometer does not work if the speedo is not going and both will work at the same time.

Thanks for your help.

Cheers

Neil

 

Right,

Just heard from the mechanic that the speedo it self is dead. It has been sent off to see if it is repairable. He swapped in another unit and it worked fine.

cheers

Neil