924Board.org

Wiz-PORSCHE-924 · Joined: 06 Nov 2002 Posts: 214 Location: Douglassville PA

Ok I just found the tach I was looking for. Im going to (attempt) to switch my 78 tach to the new 924s style tach. Has anyone here ever done this? What is all involved in doing this? And how do I get to the tach?
_________________
1987 Porsche 944
1978 Porsche 924
1992 Mercedes-Benz 190E
1988 Saab 900 (RIP)

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Getting the tach out is very easy, I've done it a few times as it has to be removed to get the speedo out. Just reach underneath the dash where the tach is and push on the back of the tach. It is just held in by pressure on the rubber ring that surrounds the tach (you'll see it when you get it out), you may have to give it a hard push, but it should pop out, it is an awkward angel which might be easier if you know someone with small hands. Once the tach is loose, pull it out a little and remove the wires from the back (there are 2 or 3 if I remember) and make note of where the wires were attached to the old tach and re-attach them on the new tach in the same positions. To put the tach back, just push it back in. Nice and simple.
_________________
1987 951 - M193 Version for Japan

D Hook · Joined: 02 Nov 2002 Posts: 3158 Location: Omaha, NE

For the record, the 924S tach and the earlier tachs are not identical. That is, the newer tachs have a different wiring scheme on the back than the older models, using more wires and a plug-in type harness, plus it has a small lighted shift arrow on the front.

Having said that, I'm pretty sure someone with the 944 electrical schematics could figure out which connections can be used to make it work in the older model. Gohim maybe? Or Vince?

Wiz--Sorry for the earlier misinformation.

Sleykin · Posted: Thu Jul 29, 2004 11:13 am Post subject:

Interesting .. the 924S tach gets it's signal from the DME. I thought the early 924 tach was a conventional tach getting it's signal from the coil?
I was under the impression the 924S tach was essentially a voltmeter and the 924 tach was an analog frequency meter?
Just curious now...
_________________
Glenn Neff
Medford, OR
87' 924S

D Hook · Joined: 02 Nov 2002 Posts: 3158 Location: Omaha, NE

That's very possible. I was under the mistaken impression they were interchangeable but perhaps not.

BTW, anyone got an older style they want to get rid of? Wiz is looking for one and I was going to send him one from a 924S but no point if he can't get it to work.

Sleykin · Posted: Thu Jul 29, 2004 1:45 pm Post subject:

I don't know for sure that they are not compatible but I do know the S has a plug type connection.
_________________
Glenn Neff
Medford, OR
87' 924S

Eturbo924 · Joined: 09 Nov 2002 Posts: 2212 Location: Londonderry NH

I have some 944 style with yellow face.
I actually am going to convert my older 924 to use the 944 face since I changed out the rest of the instruments and ran into the same issue. the 944 tac will not work with the older 924 system.

Eric
_________________
1982 924
1992 968
2003 C4S
Parts Parts Parts and More parts.
E-mail me for parts you need!
Drive Fast!

D Hook · Joined: 02 Nov 2002 Posts: 3158 Location: Omaha, NE

Eric:

Thanks for the confirmation.

numbbers · Posted: Sat Jul 31, 2004 8:35 am Post subject:

Anybody else want one of these tachs, there are two on ebay.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=2485556755&category=34206

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7913405219&category=6763
_________________
1980 924 Turbo

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

Have haven't had the dash of my 924S apart, so I can't comment on the differences between the 924 and 924 tachs.

But, the size of the tachs in both cars is the same, and if the only change desired would be the replacement of the face from the existing tach to that of the 924S tach (and the necessary recalibration of the tach). I would think that a VDO Instrument Shop could make the necessary modifications.