I purchased a small, 2" dia, VDO Volvo Tach that fits in the center console area above the little tray for small change etc. It works, sort of. When I hook it up, Green (-) wire to negative side of coil, red (+), to battery, and black to ground, it registers rpm but the engine does not run smoothly. Also the rpms are not accurate. Checking with a proper Sun tune up kit, when rpms are 1500, the tach reads about 1000. The tach was made for Volvo because it says 'Volvo' on the face. Is it possible that this tach is for some other kind of Volvo, maybe a turbo or something or maybe one with different electronics? My 1981 is K-Jet with Bosch electronics. Its not the Chrysler set up.

well, if your reading 2/3 of the RPM, I bet you have a tachometer for a car with 50% more cylinders. Some of the VDO tachs are switchable for 4 & 6 cylinders.

I talked to VDO and they were of no help. They referred me to Nichols Speedometer in Greensboro, NC, and they were of no help either. Seems nobody there is old enough to remember anything as far back as 1981. We know it's a Volvo tach because the word 'Volvo' is on the face of the dial. VDO suggested that it might be from a 6 cylinder Volvo or a diesel Volvo, or one with a different ignition set up. If anyone has heard of a small Volvo tach like this please let me know. It's of no use to me now so if someone wants it, pay the shipping and you can have it for free.

Before you give up on it, take the time to get some clear, detailed photos of it, back and front. Post the photos here. One of us may be able to tell you how to use it, or become so envious, send you money to own it ourselves.
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Art Benstein near Baltimore

Because one stroke isn't enough and 4 strokes waste 2. (Early Saab?)