shift light on tachometer

[wellsmokey]

I know it's not the most urgent or important topic to date, but does anybody have any suggestion for fixing the upshfit light on the tachometer guage in the 1988 911 Carrera Targa (and don't say the bulb).

[Jim T]

Wow, most people want to know how to "unfix" it, if you know what I mean.
Why do you *want* that light flashing you in the face trying to tell you when to shift??

[wellsmokey]

For some reason, I can't quite explain, but it bothers me that it is the only thing that is not working on the car. When it does work, I do not really notice it, but I do notice that it is not working.
Is there some module that is attached to the transmission, or is it something that is controlled in the guage itself? Anybody, Anybody?

[Marshall Reddin]

The upshift indicator is controlled by a signal from pin 11 from the computer (Brain, or more properly the DME control unit, located under the driver's seat)to pin 3 of a four prong plug located under the instrument panel, then to the connection on the tach. You probably just have a bad connection. But, it's not worth the effort!

[Jim T]

Yeah, I know that feeling, too.
I guess if I had the upshift light and it wasn't working, I'd want to fix it to.
But, then I'd disable it.
It seems better to me when I have disabled something like that, knowing that I can reconnect it if I want, as opposed to it failing on its own, it is somehow different.

[MarkY]

My shift light is acting erraticly and while I realize it isn't a major problem, I'd like to fix it.

Someone in an above post mentioned the DME unit. If I replace the DME unit, will this fix the shift light problem? Is there anything else I should check?

Also, can anyone point me to a procedure for performing this task? I have a Bentley but it really makes no mention of replacing the unit. Does the driver's seat need to be removed in order to get to the DME?

Thanks

[Mrdi]

Seems to me there were several posts re: keeping an extra DME in the glovebox as a spare as these items typically are the ones to leave you stranded somewhere in Texas. Put a new one in on an 88 and save the old one to use as a spare when you go armadillo hunting. It should last another dozen years . Perhaps your shift light may begin to function again as a result. Regardless, you've taken another step towards reliability.
Mrdi

[MarkY]

I lied about the Bentley. Replacement procedure is listed under ECM in the fuel injection section. Page 240-13 to be exact.

[MarkY]

I've been told that this might not be the DME. Can anyone suggest something else I might check?

Thx

[sleepdoc]

Mark
Look again at Marshall's post above.
If your car is running, and the tach is reading this is not the DME, nor is it the DME relay.

This is almost for sure a connector problem.
Unlikely at the big DME connector, so either the four pin connector at the dash or at the light, or the light fixtures ground, or the light is indeed out.

If you really want trouble shoot it, disconnect the DME connector, put 12 volt on pin 11 of the harness side of the connector.
If this doesn't light the light look for the
12V at the 4 pin connector behind the dash, if its there look for 12V at the connector to the bulb. If its there the lights out or ground is bad.

best Mark Robinson

[ghanlon]

Holy S*@t wellsmokey, finally, somebody as anal as I am . You must be a virgo!!!

------------------
ghanlon

[yayo_ayala]

Thanks Sleepdoc, you instruction a very helpful. I gonna be honest, I shouldn't start reviewing this little issue. It is a pain to remove the steering wheel and other things. Unfortunately I already started and it looks that I am only missing the ground.

How does the Tachometer gets the ground? I don't see touching any metal, it has a ruber around it and the dashboard has a vinil; therefore it is not by touching other piece or metal.

[yayo_ayala]

Hi Guys, I don't think in my case there is a cable issue. I checked continuity from DME/Pin11 to connector PIN3 and it is working. Therefore I think my problem is in the DME or tachometer.

I connected the Pin 3 with the tester and drove the car, but the light doesn't come up. I am not sure if that is an option to test the DME.

Once I discarded the cable, is there a way to test the tachometer or DME?

[GH85Carrera]

I fully understand the desire to have every system function like it should. I am much the same way.



That light really bugged me and I found a MUCH better use for that space on my Tach.

I never liked the shift light, but I do love knowing without a doubt that the alternator is doing the job, and not gone nuts and running at 18 volts or died and doing nothing.

As a double bonus, if the voltage just drops to 12, I know to stop and make sure the fan is still spinning and providing cooling air. I can drive a while on battery power alone, but not far at all with no cooling air.

[RSBob]

I understand as well but draw the line at the door buzzer. It’s always the first thing I pull on a car.

[RPV911]

So mine never worked and I figured the previous owner had it disabled since I noticed the tachometer had been opened before. I had a bouncy needle anyway so decided to drop it off at Hollywood Speedometer. Lucky for me it was down the street from work. They had it restored in 2 days with new glass too!!! I never mentioned the light not working so to my surprised when I plugged everything back in it worked!!! Turns on when I should shift for economy then on again at redline. I was in the same boat as the OP, I wanted everything to work. Even spent a day unclogging my windshield cleaner reservoir and replacing the pump to get the windshield washers working again. It’s a nice feeling when everything works like new. Anyways, chances are it’s disconnected from inside the Tachometer. Good luck!

[yayo_ayala]

Thanks RPV911, I was wondering if there is a way to test the tachometer without opening it. I am not sure if I could feed 12V at the 3rd pin directly in the tachometer, if it is possible which pin is the ground?

[yayo_ayala]

This weekend, I gave up and pt everything back together and I got the surprise that it started working... definitely there is an issue with the ground. Now time to search for it.