Testing a 6cyl Tacho [electronic] ??

[britishcarfreak]

How do you test a 2000/2500 electronic tacho?

There's an earth on the body of the tacho and theres a flat spade terminal and a plug type terminal.

What does what? Anybody know?

To test one do I run a lead from the coil to the spade bit or the plug bit in the back? Should the ground be connected to the tacho body or one of the other bits?

Help - Help.

Someone I know has a busted tacho and I'm about to go through a box of spares to find a good one.

 

[piman]

Hello Glen,

there are two distinct types, the one you are describing sounds as though it may be the earlier current sensing type. This is identified by a white wire on the back, one end with a female bullet connector, the other male. To test this type connect 12 volts to the two lucar spade connectors, negative to the case, of course.
You then need to disconnect the coil supply and connect to the white wire (I'd guess at the male bullet, and then connect from the female bullet to the coil. The coil current is sensed by the instrument.
The latter type has the same 12v supply connections plus another spade (It may be smaller in size, this just needs to be connected to the coil negative terminal, i.e. the distributor connection. I can't remeber exactly but there are probably some identifying legends on the case for termination.

Once connected, run the engine and compare to the car's tachometer.
Hope that helps,

Alec

 

[britishcarfreak]

Interesting.

Does anyone know why they commonly take quite a while to start up? Mine takes either a big rev at start up or a good 20second wait before anything registers.

 

[steve99]

I have a 79 TR7 and mine takes a while to function as well.

 

[piman]

Hello all,

mine does as well, I haven't bothered to find out why as it always (eventually0 works.

Alec