Odd Odometer Question
 

Hi,

I have a 1977 911 S Targa and a while back I took the speedometer out of the car to fix what I thought was the broken gear issue because the odometer wasn't consistently working.

After getting it back together and driving the car for a while, I noticed an odd issue. I'm not sure when this started but now if the car has been sitting overnight, it seems the odometer doesn't work for a period of time when I first start the car. After driving for somewhere between 5 and 10 minutes, the odometer starts working and seems to operate normally. After it is working, when I turn the car off and then have it sit for a bit, when I start the car, the odometer is working fine. However if the car sits for a lengthy period of time, say overnight, it happens again.

Before I go down the road of removing the speedometer and taking it apart, I thought I'd check with the Pelican brain trust to see if something else might be happening?

Thoughts?

That's odd behavior. If all of the gears are good and not binding, then the only thing it could be is the stepper motor might be going bad. I've seen them intermittently fail to start and I've seen them stop working when they get warm, but what you're explaining is a little different. I doubt it's the IC because I think it would either work or not.

Was there an issue with speedometer not working in conjunction with mileage not registering on the odometer including the trip meter?
It could be the pulse sensor at the trans connection either loose, dirty or broken terminal.
I have a stock ‘77 VDO electronic speedo fyi.