1989 Carrera Targa Speedo Sending Unit fix

[Iracema1]

Hi Everyone:

My 1989 Carrera Targa (115k miles) has a maddening speedometer issue. It will, suddenly, just stop working! I can't calculate mileage on tours, etc., so it is important to me!
Already spent $$ having the speedo unit redone at Palo Alto speedometer, so I have isolated (I believe) the remaining problem to the sending unit. Before I spend more $$$ to replace that, is there any home-gown repair that anyone has done with their sending unit? Any lubrication/cleaning/servicing that can save me now that I have already spent on the speedo?
Any suggestions appreciated!

Best

Andy

[bemmett]

I've actually got a bunch of speedo/odometer related threads bookmarked, I'll see if I can dig them up once I get home. I seem to remember that issues have ranged from dirty magnets in transmission to concerns about there being transmissions that had 4 magnets vs. 8, to new senders not being seated properly (too deep; a plastic washer apparently solved one guy's problem), to wire chafing in the transmission access panel.

I was having similar issues, as well, as both the speedo and odometer were reading 2x. The previous owner had complained of this issue in the past, and replaced the sender about 1 year ago but still had issues. He had the speedo sent to PA Speedo for calibration, and the issue persisted. After I took possession of the car a few weeks ago, I took it over to Hartmut at PA Speedo to let him dig into it. The speedo was still perfectly calibrated, but the new sender unit the previous owner had installed at a shop in the East Bay was not an OEM part. Upon installation of an OEM sender, everything worked perfectly.

YMMV, but that's what worked for me. I guess sometimes it's worth to pay the OEM parts premium.

~Brian

[Iracema1]

Thanks! I am not knowledgeable (yet!) about these cars and will probably take a more official fix. It seems like there are an awful lot of variables.
Engine/Transmission were out of this car about 5k miles ago, (clutch, valve guides, etc.) and I suspect that something happened during re-assembly.
Best and thanks

Andy

[bemmett]

Heheh. I'm not particularly knowledgable yet, either. This is my first 911, and I've only had the car for two weeks so I'm still learning as well. I primarily wanted to get a few irritating issues (speedo, smog+registration) out of the way first before I started getting into the wrenching myself.

Good luck!

[CCM911]

You say the engine was out a little while ago?

Check the connections under the hatch by your shift coupler. On the floor in the rear center, under the carpeting(just in front of the rear seats) you will find a cover held on by four screws. Remove this cover and you will see where your speedo wires come through the center of your car. Take a look at the connectors. One of mine was broke, so I repaired it. If you have a bad connection, odd things will happen.

[Iracema1]

Great advice CCM911 and everyone. I will surely be checking the connections for an obvious issue before taking this to the shop!

Best and thanks so much

Andy

[kodioneill]

The guy that dropped the engine may have left the inductor connected and pulled the wires apart as the previous poster stated.