Tachometer Help and Dash removal/clean help

[Bon Voyage]

Hi folks,

I've got 2 things I hope somebody out there can help with. First is the tachometer on my bus is a little wacky. It usually sits around the 1100 rpm mark or so when the engine is off except there was a few days where I noticed it was sitting at around 6000 rpm. When I drive the bus it seems to usually operate fine (I can't be sure it's accurate though) but there was a few instances where I know it was showing higher than the actual rpm's. Any idea what this could be?
(picture attached with engine off)

The second picture is my dash coming apart so I can clean in there a look at heater connections that I don't think are working quite right. This black piece below the window has all the screws out but it won't pull out, it's attached to something underneath but I don't want to yank it and break something. No screws underneath. It's a 2001 Thomas MVP rear engine if anyone happens to have experience with this.

thanks

[o1marc]

Electric speedos bounce once the juice stops and rest whereever they want. Yours is no different. Can't explain your difference while driving, need more details.