Tach and Speedo not working after engine rebuild - '87 Carrera

[alfisti]

Hi folks. I had the car in for an engine rebuild, which the shop took longer than planned. I don't have a problem with that - we worked it out. But since the car sat for so long, I am wondering if there weren't a few casualties.

Both the tachometer and the speedometer aren't working. The tach doesn't budge from the zero position, and the speedometer doesn't advance at all. The turn signals, shift light, hi beam indicator all work.

Is this a mechanical failure, from sitting? It's my experience that old mechanical parts, when not operated for a period of time, are likely to freeze up... but the failure of both the odometer and the speedometer seems a little too coincidental.

It also seems unlikely that during the process of the engine rebuild, they would have touched any connections on the DME or behind the dash, so I would not suspect wiring problems...

Unless there is something they forgot to plug in, in the engine compartment. Is there a connection I can check? Or maybe a fuse to check?

I have searched this forum and see a lot of info on swapping tachs due to engine swaps, or problems with mechanically broken tachs... but this seems to not fit the other scenarios.

Of course I can just take the car back to my mechanic and have them look at it, but 1) I want to wait a bit and drive it, to see what else (if anything) needs attention, and 2) I've been without my toy for a while, and can't wait to drive it.. :-)

Also, if this is an easy fix, it would be easier than dealing with dropping the car off again.

Ideas???

Thanks
-Glenn

[Trakrat]

Originally Posted by alfisti

Also, if this is an easy fix, it would be easier than dealing with dropping the car off again.

Ideas???

Thanks
-Glenn

I'd suggest taking a look in the engine bay and checking all the wiring to make sure something isn't disconnected from within the engine bay.

Just from what I've learned so far, it would be easy to forget to plug something in.

[Flat6pac]

The Speedo connection is located on the side of the trans, did they remove it there?
There is a connection in the back seat access to the tunnel for two wires that come off the trans just mentioned.
The tach is driven off the brain with the connection in the front under the carpet
The connector is a small flat four wire connector with two small black wires, one yellow and one black/purple tach drive wire.
Bruce

[alfisti]

Thanks, I will check!

[alfisti]

Bruce, are you talking about the access panel between the seats on the floor, behind the center console?

Thanks

[proporsche]

hi..here are your wires Bruce is talking about-
Ivan

http://cdn4.pelicanparts.com/techarticles/101_Projects_Porsche_911/37-Shifting_Improvements/images_large/Pic3.JPG

[alfisti]

That's what I thought. Thanks

[alfisti]

I just removed the panel, and checked the connections. Seemed like they were firmly connected, I didn't unplug/replug. I guess next step is jack the car up, and check the connections to the trans?

Thanks

[alfisti]

Sorry - I just did some more research, and it looks like the sensor wire is part of the sensor.... so if there is a connection problem, it would be in the connections in that small access panel, right? I'll unplug and plug back in.

[proporsche]

hi..just thinking about your problem..are your lights in gauges on when you pull the light switch?...wild guess about the grounds to the gauges.I know you have the up**** on ...just a guess;-)

Ivan

A

[alfisti]

Hi folks. There is only one connector in there that can be disconnected.


https://heartofgold.smugmug.com/Speedo/i-KCqDk6F/A


It's the white connector with 2 brown wires. I expected black and purple.... am I looking at the wrong thing?

Thanks

[proporsche]

just green and brown..............no white..

[Flat6pac]

You can’t expect black/purple there because there is no drive for the tach in the back on a 3.2. it’s in the front, previously explained
Bruce

[alfisti]

Ugh. I just took the car for a drive and realized, I was apparently not 100% alert when I posted this yesterday.

The SPEEDOMETER works just fine. What doesn't work are the TACHOMETER and the ODOMETER.

Not sure what made me post the wrong info yesterday- sorry.

For tach/odo not working, is there an easy fix? I will likely bring the car back to the shop on Friday, but I'd love to solve this myself.

Thanks

[Flat6pac]

The odometer is self contained, the drive gear goes bad inside
The tach shouldn’t have anything to do with motor removal
Bruce

[alfisti]

So, maybe the odo gave up the ghost from sitting.

The tach - seems odd it would choose now but maybe also from sitting around. :-(