Tachometer (REV Counter) reading 50% REVS

[Phenex]

My car since it has had a body off chassis refurb, is only registering 50% of the REVS i.e. what used to be 4000 RPM is only showing as 2000 RPM.

The car has a new battery and new cable from the alternator, but any ideas what could be causing this issue.
I posted on Facebook and got 100 AMP fuse, and some resistors but theses have been checked.

Cheers

Jay

[MarkwG]

Afaik the rev counter has an adjuster which needs to be set for the correct engine. I don't recall the procedure, but mine over reads for tge same reason. I'm away atm, if no-one else posts the answer I'll have a hunt when I get back.

[Byker28i]

Big fuse cause the rev counter to be jumpy. Sounds like its reading half the revs

[notaping]

If the car's running ok then it can't be the crank sensor and is probably just the tacho. If yours is adjustable - this might help . . .

https://www.smiths-instruments.co.uk/app/uploads/2...

[Phenex]

Thanks for the information.
Any idea how the calibration could be the cause as, I wouldn't have thought a body off should affect it (BTW Rev counter worked perfectly before).

[MarkwG]

There's a selector on the back of the unit, might have got knocked.