tachometer connections correct?

I have a sunpro tach with four(4) wires. White, black, red, and green. I have the White on the headlight switch, and this wire sees 12volts when the headlights are turned on. I have the black wire on the chassis under the dash, it is a good grounding point. The red wire is connected to the wire on my ignition harness that sees 12volts only when the car is running. The green wire is connected to the white wire at the harness on the coil packs of the engine. I have verified this wire as the tach signal wire by testing with a DMM. It shows about 2.5volts AC at idle and goes up to about 6.5 volts when revving. As far as I can see, I am not missing anything, however, I am still getting no reading on the tachometer gauge. When the ignition is on, the tach needle moves from a position below 0rpms, right up to exactly zero. The gauge's backlight comes on fine with the head light switch. Everything appears to be working except the actual tach reading. Is there something I'm missing, or am I just lucky enough to have a malfunctioning tachometer? It was new when I bought it. by the way, this is on a 1991 cutlass supreme. thanks in advance for anyone trying to help. -Dan

Dan, When I do remote starts I always like to find the tach source so your problem interests me. Although I'm no expert like many on this forum I see a couple of things you might check. Do you have these instructions or something like it? http://www.tradervar.com/All%20Other%20Sun%20Tachs.pdf If so I'd start with the basics - Check your cylinder selection to make sure it matches the car. - Hook up the unit temporarily like they say; Red to + of battery, Black to - of battery, leave white off for now. Now that you've positively ruled out those three connections you can search for the correct source for the green one. Try the ones you've used already. It looks like the white wire should be the one. - You might try leaving a email on Sunpro's tech help or look up your engine on their site for details on wire color location or settings. I couldn't find Oldsmobile on the site, but maybe Pontiac uses the same engine in one of their cars. If all else fails list some more info on your car--engine size and type, etc. Maybe someone with a buick or something had this problem but doesn't recognize your engine from the Cutlass Supreme name. Hope this helps. Rob

okay, I'm not to sure about amreican cars but I know that some of our aussie cars wont accept an aftermarket tacho easily due to the fact that the low tension lead is actually (-)! andnot a positive, very easy to miss on a multimeter..especially when you think that tere is no chance on it appearing. Mind you it is a negative signal and not a variable earth. please bare that in mind