Anyone know what the output voltage of the tach amp is supposed to be?
I'm talking about the wire that leads from the amp to the gauge, I thought it delivered a voltage to the gauge that varied with engine speed. Mine has 12 volts...well, like 12.87, it moves around a little, buut what the heck does that mean?

I've got a tach amp that supposedly works...from ebay of course, but they said they tested it, whatever that's worth...I added a wire to my receptacle in the appropriate location (I have a euro with no stock tach) and ran it up to the gauges. Now, when I start the car, I get 12 volts out of that wire, and it doesn't vary with engine speed. Just for kicks, I connected it to the "TD" pin on the back of a tach, connected power to the pin with the "+" sign next to it, and held a ground wire on the back plate to ground. Nothing...I was't really surprised.

Anyone have any input? Is there a way I can test this amp?

Thanks,
-Geoff

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

Okay, I thought about it overnight while I slept...I think the best thing to do is to test my tach amp in another car with a known working tach.

Anyone in the central Pennsylvania area? Near Harrisburg? Can I try my tach amp in your car? One question for the group...if the amp is bad, could it harm another person's car? I don't want to mess anyone else up...

Thanks,
-Geoff

__________________
1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now