Connecting New Tachometer
 

I recently purchased a used VDO tachometer(part# 230/085/001) to replace the stock unit in my '84 911 Carrera. I was led to believe that it is an older(70's probably) unit from a 911, but the PO does not know for sure. It is identical to the stock one in every way except that it is an 8000 rpm tach, and more importantly it has a three-prong electrical connect in the rear as opposed to the six-prong connect on the stock unit. My questions are, can I use this tach? Can this be used with only three of the connectors(or is there a definitive need for all six)? If so, which three(top row or bottom row)? Should I rewire the tach with the correct connectors, and if so any advice on how to do so?
By the way, this is my first post and my first Porsche, so go easy on me. :)

Shark

Bump cause I don't want to blow up my electrical system!

Let's first figure out what tach you have. The part number you listed isn't really the part number. Look at the inside rim of the gauge, at the top. There will be a very tiny set of numbers, 911.641.303.01, or similar. Let us know what you find.

JR

Was there something wrong with your original tach and that's why you're switching? Why are you going to an 8K older style tach?

Aha! If that is the case then the part # is 911 641 301 29.
Dan: Mechanically there is nothing wrong with the original tach, but cosmetically it is somewhat challenged. I put what I thought was a lowball bid on an ebay tach, and won it. The new one seems to be perfect cosmetically, but might not be mechanically viable. Upon further inspection, the connectors are in no way compatiable as they are a different size prong or din(I think that is the right word for that connector). I also suspect that the extra connections are for the Computer Assisted Shift Indicator System.
Any help would be appreciated guys.

Shark

OK, that crosses to a '74 - '77 tach for use wth 3-pin CDI and a points-type distributor! Some have reported getting them to work with Motronic engine conversions.