older tach in newer car

[xbmwguy]

trying to wire a 82 n/a tach into my 87 turbo but no love. my 87 has power,td, gnd, - the 82 has td, power,td,- any help will be appreciated

[Flat6pac]

I believe but with reservation, the 82 has the rev limiter built into the tach so it ll be one of the negatives to ground the ignition.
Bruce

[xbmwguy]

bruce that makes sense as my boost guage in my tach works off a neg ground as well

[Walt Fricke]

The '82 tach and rev limiter wiring works like this:

The tach signal wire starts at the 6 pin CD box. That goes to the TD terminal on the tach. Crimped into the connector for the TD is another wire, which continues on to a unit which looks a bit like a relay, which is in the area behind the instruments and over on the left. Accessible by pulling the oil level gauge, or by getting behind all the fresh air stuff from the trunk side. That unit is the rev limiter, and it controls the fuel pump relay. When you hit the limit, the fuel pump cuts out.

I don't know how or why your tach would have two TD terminals. Leaving aside the lights, all it needs is power, ground, and the tach signal.

By the time of the '87 NA cars, there is the DME, plus a module for the shift light, to complicate things. But your turbo is still CIS, so I suppose doesn't have the DME. The '82 has a largish electronics box under the passenger seat, but it is not an ECU - it controls the frequency valve and some warm up stuff. So its tach might still be wired up the way the '82 was, with a separate rev limiter unit.