Tachometer sticking on cold mornings

[ATL Cruiser]

1992 HZJ77 automatic

My tachometer sticks at 0rpm on cold mornings until hitting 1200rpm. At that point it "breaks loose" and then works completely normally for the rest of the day.

So far I have tried:

• Cleaning the ground point at the battery
• Cleaning the ground point behind the engine
• Replacing the tack pickup

I'm at a bit of a loss here. Has anyone else dealt with this?

 

[Gun Runner 5]

In the olden days (may not be applicable now) folks would spray graphite down the cable.

 

[plink01]

On my 78' Ford XC Falcon and BJ42 landcruiser both tacho's I have to tap the plastic screen twice and they spring to life! I'm unsure why but it works everytime and it's part of my start up. I don't even realise i do it it's like muscle memory.

Both are super old and fragile so I've been hesitant to pull them apart when they work fine after two taps.

I don't have anything more scientific to add.

 

[coldtaco]

I would be looking at the needle itself. I don’t have any other ideas

 

[ATL Cruiser]

Thanks all. @Gun Runner 5 I wish it were as simple as a tach cable. This one is is a wire fed signal.

My gut feel is that the tachometer has a spring shock built into it similar to the speedometer. It holds the speedo at 0mph until a certain speed is hit, and then it starts moving. This is to prevent the needle from bouncing. Sort of like a shock. I'm going to have to take the tach apart to see if that shock is present and if so, perhaps too tight.

 

[ATL Cruiser]

Update on this for anyone interested. I sent the full cluster out to Bill in Alabama (ECU specialist). He rebuilt the tach and the main instrument board. Working perfectly now.

No more sticking tachometer when cold.