Tach not settling in at ZERO when engine is OFF

[RRichards86]

Hello gang--anyone else notice that the tach on many G-body Cutlass's doesn't settle in at ZERO RPM when the engine is OFF? I know mine doesn't and whenever I see pics of instrument clusters other cars, I notice how there's don't set at ZERO either. Mine usually sits around 1500 RPM. Is this pretty much inherent on all 83-88 Olds Cutlass's? Is there a fix for this?

This of course leads to incorrect true RPM readings when the engine is running--as I just found out after having my car dyne tested and tuned in preparing for an upcoming emissions test.

Anyway--just curious if others have this issue and if there is a simple fix for it?

 

[GP403]

That's just how it is. They always worked that way. 🤷‍♂️ Not sure if there's a way to force it down to zero with no power.

 

[69hurstolds]

Leave the key "ON" all the time. Only fix for that. But it causes other issues...

But seriously, yeah, they float when off, doesn't matter though. As long as when you turn the key to on, the tach SHOULD drop to ZERO. If not, then that's something to look into.

 

[Built6spdMCSS]

Mine has been doing that even with the LS Swap. The cause is when you turn the key off and the voltage in the system hits the stepper motor.

Mine is accurate to my laptop within 50 RPM so I'll take it, running the Filter also.

 

[RRichards86]

Mine has been doing that even with the LS Swap. The cause is when you turn the key off and the voltage in the system hits the stepper motor.

Mine is accurate to my laptop within 50 RPM so I'll take it, running the Filter also.

I'll have to see just how close the actual reading on the tach is to what the dyno says, but my mechanic said the tach was inaccurate. It seems like the tach is always showing 50 to 100 RPM higher than the actual figure.

Anyway--thanks for the input--I guess I won't worry too much about it. It just bugs me that it's not right.

 

[abbey castro]

That is the way it has been in my 87SS since new.

 

[RRichards86]

That is the way it has been in my 87SS since new.

Wow--that is really amazing to me. Sounds like a built-in design flaw from GM from the get go.

 

[Ribbedroof]

Wait till you find out the fuel gauge isn’t correct when the key is off either!

Seriously though I think there’s even mention of that in the owners manual in my Malibu

 

[Built6spdMCSS]

Wow--that is really amazing to me. Sounds like a built-in design flaw from GM from the get go.

Not a design flaw, I mentioned above what the cause is.

I guess I'd be questioning my things going on in life if I'm worried about what the gauges of a car are doing when it's not even running...🤣

 

[SS_Malibu]

Mine goes to zero. 😉