Atypical Tachometer Bounce (wildly swinging on shifts)

tmaull · tmaull's Garage

Hi fellow Pelicans, I've got an issue with my recently purchased 911SC, that I've had since I purchased the car. On shifts (up or down) the tachometer begins to swing wildly. This does not appear to be similar to the relatively common bad VR tach bounce.
One fact that may be relevant is that the car has a 1985 3.2 Euro engine. I have posted a video of the issue I am facing on youtube: https://youtu.be/OCSs5cK3d68

Thanks so much.
-Tom

tmaull · tmaull's Garage

Does anyone have any ideas? Is this normal on a 911? Thanks,
-Tom

Sicklyscott · 04-17-2015, 06:51 AM

wow...that's quite a bounce! Mine moves around a bit between shifts but not like this.

Bump for an answer!

Lapkritis · Lapkritis's Garage

Could be a weak ground to the tach. I'd start there... just a little time, and no cost/free if you have a multimeter.

Early VDO Tachometer Guts

RSTarga · 04-17-2015, 09:03 AM

If you have points, bad points. Also check connections at side of distributor.

joe payne · joe payne's Garage

I believe you need to send your tach in for repair. Mine in my 78 does a similar aggressive swing like that too. Only when I blip the throttle or aggresive shift. Call North Hollywood speedometer.

1980SC · 04-17-2015, 11:03 AM

Mine used to do the same thing years ago. I swapped it out for a used tach out of another SC, and that resolved the problem. Definitely something wrong inside your tach.

Rob

dfhtrhjn · dfhtrhjn's Garage

One of my 911s does that too, the other doesn't, just a goofy tach as far as I can tell.

tmaull · tmaull's Garage

Thanks everyone for your responses! Seems like another tach is the answer. Being pretty new to the Porsche world, what's the most economical way to fix this? Pull it and send it somewhere? Or just start trolling ebay/classifieds?

gazzerr · 05-02-2015, 01:53 PM

I'm read about this and it's supposed to be the damping inside the gauge that's worn. Like Joe said - send it into North Hollywood or Palo Alto and get it repaired or find a good used replacement. My SC's tach swings a bit but not as bad as that one. They all tend to do it to some degree as they age.

DRACO A5OG · DRACO A5OG's Garage

Pull it and send it to NoHo. you can drive with out it just make sure you tape off the connectors.

This will give you a chance to really practice your shifting techniques listening for the RPMs

timmy2 · timmy2's Garage

If you pull it take a lot of photos and Mark the wires and locations they go to really well.
There are a lot of what wire goes where in my tach after they have been serviced...