Stuck Tach

[dktool]

After a 90 mile run yesterday my final engine start to blow out the exhaust after flushing resulted in this, see pic..
( no I didn't rev it that high)



The usual amount of slapping did not return it to zero, but one wave of this magic wand did it,. see pic....



It is a magnet that is used in a partical filter on the ultrasonic tank at work, it is in the pump out / drain circuit.
I don't know what type it is but it ridiculously strong !

To show how strong it is, I can move my mig / tig combo with tanks on it just by having it stuck to the sheet metal. see pic ...



The lesson learned here is when slapping doesn't work, use a magnet to move the needle back to zero.

[Metrodriver]

Did you blow up your engine? Your first sentence is hard to understand.
Using a magnet to move a needle back is something I've never heard of. Hope your gauge will work next time. I have no idea how a rpm gauge works, most other instruments use a bridge setup between the coils where 2 try to balance to neutral (=0) and the third cauaes the deflection. That caused my oil pressure gauge to spike to 80 psi with engine not running.

[dktool]

Did not blow up the engine, tach works normal.

[Metrodriver]

Great! Your magnet fixed it then.

[builderdude]

Dean, I had a similar issue years ago when the ignition switch got bumped to the off position while running at 3600 rpm. Tach was stuck at 3600, when I restarted the engine tach was still stuck but after giving some throttle it started working as expected and haven’t had any issues since.
Weird stuff…

[dktool]

When mine goes wank it happens when starting, the needle will swing wild to a high point and stick, a quick backhand or two snaps it back to reality.
Not this time.
I was about to remove it, that's when I had the magnet epiphany.