Speedo and ODO don’t work

[CjSawinski]

Sorry as I know my question is kind of vague without further information.
I haven’t been under the car yet to check that cables are connected to the transmission (and that’s all I’m hoping my issue is). But basically I know the common ODO failure information with the gear in the gauge. But the speedo not working just has me scratching my head a bit. The car is a 77’ 911, or for sure has an electronic speedo/odo as I’ve pulled the gauge from the dash and expected it was the mechanical unit and mechanical problems, but it’s electronic lol.
Outside of getting under the car to check the wire are there any other ideas?

[PeteKz]

Loose or pulled off ground wire? By poking around in the dash, you might have knocked it loose from the gauge.

[silverlock]

Don’t overthink it just yet.

1. Pop the gauge out and reseat the connectors
2. failing that, check for voltage on the +12V per the diagram below:



(I stole this from someone else’s post and can’t remember who to credit. It was super helpful when reinstalling my gauge after North Hollywood fixed the odo gear)

[silverlock]

[rs6er]

What year? I don’t think my speedo still worked when the odo gear failed.


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[silverlock]

Originally Posted by rs6er

What year? I don’t think my speedo still worked when the odo gear failed.


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Speedo on my ‘78 SC worked fine when the odo failed, FWIW.

[CjSawinski]

To clarify, the Speedo/ ODO not working isn’t because of me pulling the gauge from the dash… neither have worked for years and years, I simply pulled the gauge from the dash for visual inspection and to see if it was mechanical or electronic.
Thanks for everyone’s tips so far!

[CjSawinski]

The cad is a 77’ 911 (Coupe), it’s a ROW car straight from Germany so technically it’s not an “S” (like that matters though lol).
I don’t know what a kilometer is anyways so not sure why I even care if it works or not hahaha.

[jbell959]

Where are you located? If you have a multimeter, I would check to make sure you have power and good ground to the speedometer. If that checks out then you can do a quick test by connecting a wire to the speedometer, in place of the wire coming from the sender, and just quickly tap it on and off ground and the speedometer needle should bounce.

If you run out of ideas and you're in the US, I'd be happy to test the speedometer for you.

[CjSawinski]

Thanks jbell, ya I’m in the us (Minnesota). I have a multi meter and I’ll give that a test this week when I’m working on the car again.

[CjSawinski]

Originally Posted by silverlock

Thanks for this pic!
My Speedo/ Odo is not plugged in like in this picture. I guess maybe my dad monkeyed with it 30 years ago and didn’t plug it back in properly, that’s all I can think of anyways.
Now I just hope I can move the two sensor plugs down 1 each and it’s that easy. That’s what’s different about mine from the pic.

[CjSawinski]

Here’s how my wiring looks (again I have NOT touched any wires or unplugged anything).
https://imgur.com/a/VFpWqJG

(Haven’t figured out how to is photos directly from my phone easily on the forum yet lol)

Oops haha, I think I figured it out (the files are IN the computer)

[CjSawinski]

[jbell959]

Remove the 2 wires from the connector I circled and move them to the ground connector on the end.

[CjSawinski]

Originally Posted by jbell959

Remove the 2 wires from the connector I circled and move them to the ground connector on the end.

Thanks! I already did that last night. Now to check that it works after that one of these nights soon, I don’t have brakes on the car atm so I’m thinking I’ll just put into gear on jack stands (even though that sounds like a bad idea to me lol). Otherwise I don’t plan to have the car back in the road until next spring but I’m dying to find out if it was just that simple.
Bad idea to run the car on jack stands with the rears in the air (even if only in gear at about 5mph to verify the speedo now works)?
Thanks for everyone’s help so far!