The Triumph Dolomite Club - Discussion Forum

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?

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

Magenta Auto Sprint wrote: ↑Mon Jan 08, 2018 8:11 am 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.

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

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!

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