Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Erratic Tacho

The tacho needle on my Three Wheeler is erratic. It's ok when I start off but fluctuates wildly after a while.
Is it likely to be the tacho or the sensor?

What year?
The sensor used for the rev counter would be the Crank Position sensor and if that was being erratic then so would the engine running.

I guess that without engine erratic running as well it's either the tacho itself or a supply wire to it chaffed maybe? Checking the loom would be the cheaper first option. I would break and make the tacho supply plugs a couple of times in case it's just a dirty/poor plug pin contact.

My initial odometer issues—involving a fluctuating needle—were caused by a broken rigid metal wire on the 2,000-ohm resistor; after repairing it, it worked for a while, then only intermittently (specifically in hot weather), before failing completely. I purchased a Harley-Davidson sensor of a different size, fabricated a custom bracket to avoid altering the original mounting location, and reinstalled it with a 2,000-ohm resistor, creating a new wiring harness that placed the resistor under the front hood; it has worked perfectly for four years.
The original resistor is located in the wiring harness, approximately 20 centimeters from the sensor.