Sprint rev counter

[cleverusername]

I finally have the Sprint engine idling stably, after turning down the settings on the carbs allot.

Alas the Sprint rev counter I have doesn't work. I just want to check whether the Sprint counters work off the coil negative terminal like the 1500 ones?

I also have electronic ignition, a britpart module. I understand not all rev counters will function with these?

Could I check it with a signal generator?

Oh and I don't like how close the exhaust manifold is to the side of the car, has anyone heat proofed these areas?

[Magenta Auto Sprint]

the sprint rev counters do work off the coil.

I made up a test loom for my spare rev counters so that I could connect them to the coil in the engine bay.
sometimes you have to tap the glass to wake them up, seems to be a common problem.

My 1850 has a luminition unit fitted and the rev counter/tacho works fine with that, other electronic ignition units may be different.

Not sure how you would test a tacho with a signal generator, maybe google can assist.

Malcolm

[cleverusername]

the sprint rev counters do work off the coil.

I made up a test loom for my spare rev counters so that I could connect them to the coil in the engine bay.
sometimes you have to tap the glass to wake them up, seems to be a common problem.

My 1850 has a luminition unit fitted and the rev counter/tacho works fine with that, other electronic ignition units may be different.

Not sure how you would test a tacho with a signal generator, maybe google can assist.

Malcolm

My theory is a rev counter works by reading the pulse from the points switching on and off. In theory this pulse will look like a waveform on an oscilloscope.

So in theory you could use a signal generator to send the same function to the rev counter and get it working. I am not sure what function would be correct. I suspect a square wave, as the point are suppose to switch off pretty rapidly.

Anyway the loom is homemade, so the first thing I will do is check the wiring.

[Triumph1300]

Square wave is good enough for testing, it's actually not true square in function, but it'll work

[xvivalve]

Apart from the 'red line' location, the Sprint tacho will be identical to the original 1500 one. Easy test by elimination if you knew the 1500 one worked before!

[Toledo Man]

I might just have a spare somewhere in my stash...