Tachometer issues

[Hay Dude]

Massey 7495 tractor with traditional dash cluster tach. After running for a couple hours and presenting correct tach speed (compared to digital readout), the tach goes past the correct reading (2000RPM) creeps up towards 2500RPM, then into the white zone and sits just there.
Turn tractor off and it corrects itself, reads properly and 1-2 hours later, it does the same thing.

Any thoughts on cause or repair?

 

[WranglerX]

Had similar issue with a 2005 Chevy Truck.... The (stepper) motor/drive mechanism that moves the needle was bad and had to be replaced.... In fact all the whole dash had to have drive motors replaced in all the gauges.... Quality issue with Chevy...

 

[Patches]

GM has had this issue for a while. I had a 1993 GMC 1/2 ton, bought new and it had a history of gauge issues. Dealer replaced the dash pod numerous times and it still had the problem when I sold it 7 years later with 125,000 miles on it

 

[WranglerX]

GM has had this issue for a while. I had a 1993 GMC 1/2 ton, bought new and it had a history of gauge issues. Dealer replaced the dash pod numerous times and it still had the problem when I sold it 7 years later with 125,000 miles on it

Had a aftermarket speedometer facility rebuild mine (maybe 10 years ago) and so far its still working fine today ....

 

[jigs_n_fixtures]

I had 2001 Chevy work truck. I drove a out forty mile out of town to do some stream measurements, and bit if surveying.

When I got to the site, the speedo dropped down to 35, as I slowed down to turn off the highway, and stayed there.

on the way back to town, I guessed at the speed, by using the tach, and got pulled over by one of the deputy sheriffs.

The look on his face when he asked if I knew how fast I was going, and I replied, “The speedo says 35, but it started saying that about two hours ago. So, it is probably wrong. And, since you pulled me over I,d have to guess at least 75.”

We had a short talk, and he decided to let me off. Once he told me how fast I was going, I could figure out how many rpm to turn to drive 65.

 

[number two]

Do you know if your tachometer is cable driven or electronic?
Will help.
Good Luck!

 

[dirttoys]

Good above, speed sensor or cluster is heat sensitive, hopefully not the cluster, and not too expensive to replace.

A little can of duster air held upside down and sprayed on components will often help trouble shoot heat sensitive "stuff".

Best,

ed

 

[ptsg]

Have you tried some "love taps" behind the cluster to see if the needle reacts?

Had a similar issue on a 25 year old Mitsubishi Pajero/Montero, where the solder on some resistors for the tach would break and it would work intermittently. A couple love taps would get it going, which only proved about the broken solder.