tachometer

[BIGGLESSNOOKER]

Advice required re my Tachometer. I have three dials on my dashboard : Temperature, tachometer and oil pressure.
Occasionally my tacho drops to zero ,all other dials function normally , and then reverts to normal . Anybody got any ideas?

 

[Momac]

Clean electrical connections to the alternator and make sure they are not loose. May also be worth doing the same at the tachometer.

 

[rafiki_]

Check the alternator drive belt. My tachos are driven off the alternator, and stop working if the drive belt slips.

 

[aquatom]

We need to know what engine you have?

 

[Jcorstorphine]

Tachometers have different ways of reading engine RPM such as a wire from the alternator or a dedicated sensor which can be off the crankshaft or the flywheel so it not easy to advise so think you need to do a bit of digging.
My tachometer has few hiccups now and again but a quick tap gets it back on track. My tachometer is run from the alternator.

 

[BIGGLESSNOOKER]

Its a 1500cc Thornycroft on a broads cruiser . I'll check fanbelt when I get back next wednesday . Thanks for advice.

 

[Jcorstorphine]

Pretty certain your tachometer is run from the alternator so would suggest you look at the connections. From memory, I am sure it's the "W" connection.

 

[lancingmike]

If tachom is driven from the alternator, as they usually are, may be a problem withthe alternator itself.
Does the red warning light come at the same time as the tacho drops to zero?
If not next search would be for wiring failts.

 

[peteK]

I had similar problem with tachometer dropping to zero and not charging,turned out to be dirty brushes on the alternator