Analog Volvo tach testing question

[ancora]

How does one bench test an analog tachometer?

 

[Tired Trawler]

Greetings!
If you have twin engines, just swap the tachs from side to side, & start the engines to test.
If you dont have twins, what exact model of Volvo are you working on?
Do you have a Volvo instrument panel or aftermarket panel?
If a Volvo panel is fitted, who is the tach manufacturer?
What color is the pointer?
Is there an hourmeter in the tach face?

 

[Bmarler]

Cable drive or electronic?

 

[ancora]

I replaced the analog tachs on the bridge with Aetna digital tachs 25 years ago. I kept the two analog tachs as spares. Now I have a "lazy" analog tach on one engine and would like to replace it with one of the spares. The tachs are driven off a signal from the alternator. The tach has four spades on the back, positive, negative, W and G, referring to the wire colors.

 

[Bmarler]

I see. Your best bet is to just swap one out on the dashboard since you have working spares.
You could bench test one, but you’re need some tools to do it. Either a pulse generator, or maybe a power supply/encoder to send back a signal.