Tachometer problem

sd01 · 10-21-2001, 07:37 PM

Hi everybody,

From day one of owning my 1984 944, the tach has rarely if ever worked. Once, over a year ago, it showed signs of life, and also a month ago at 60mph+. Other than that, nothing. I bang on it, bang on the dash, nothing. But the mpg reading has always functioned. Can you guys advise where to start on fixing this?

Thanks!

SD

Britwrench · 10-21-2001, 08:08 PM

Get another tacho from a junkyard or send the one you have to a shop. They all fail eventually..

sd01 · 10-28-2001, 07:27 PM

Before I hunt down a new one I'd like to troubleshoot this a bit more.

Right now, the guage moves to from zero to what is probably around 200 rpm when the car is running, and maintains that reading 95% of the time. So some sort of signal is hitting the guage, right? And I assume the tach is capable of working properly because it wakes up every once in awhile. Where are good places to check when troubleshooting this?

Thanks again,
SD

85944na · 85944na's Garage

my old tach used to work fine once in a while, get stuck once in a while, and not work at all most of the time, a 10$ used tach fixed my problem, and my mpg guage worked as well

Mrmerlin · 10-28-2001, 07:33 PM

[QUOTE]Originally posted by sd01:
Hi SD if you want to trouble shoot the tach, remove the instrument and look at the wave wires that go to the tach clean the connections if your able then try it this might fix your problem, it worked on my 928......Stan

diannone · 10-28-2001, 08:09 PM

dont use your fist, get something bigger!

gixer02 · 10-29-2001, 05:17 PM

my tach needle always moves but is right half the time... it will jump all over the place or go up and stay all the way past redline- then i hit the dash and it jumps back- whats up with that... just get another used one or can this be fixed? thx

------------------
Porsche man for life.
83' 944

AFJuvat · 10-29-2001, 06:57 PM

You have one of two options:

1. The electrical connections are faulty. pull your instrument cluster and clean/retighten everything. I wrote a tech article on this, which should be posted fairly soon, but if you want, I can send it to you.

2. The internals of your tach are wearing out. Get a used one or have yours rebuilt. Replacement with a new one is rather expensive and not recommended.

Mine stayed at zero from time to time, once I hit a bump it starts working again. once I cleaned all the contacts and did a few other things to the cluster, it cleared right up.

AFJuvat

sd01 · 10-30-2001, 02:44 PM

Thanks for the advice!

I took apart the instrument panel and checked out the wiring, everything was pretty clean. Wiggled the wires/connections with the car running and didn't see any signs of life from the tach.

Question: what are the green and red wires coming from the printed circuit board on the speedo for? They have a black connector that plugs into the tach, separate from the many smaller wires in the main connector. Is the tach dependent on the speedo for anything?

sd01 · 11-05-2001, 06:38 PM

Ok getting back to this...

I'm gonna assume that the printed circuit board is for the cruise control. Anyway, I'm pretty much set on finding a good used tach (got one to sell?). But if anyone has another troubleshooting suggestion to post, please do.

Thanks ya'll!