Odd Tac Behavior on reinstall of cluster (1 Viewer)

[caladin]

Finally chased down the turn signal issue (hacked in trailer plug) in my 82.

Went to reinstall the instrument cluster. Plugged all up, turned key to on, behaved as expected.

Started truck and the tac rose slowly to about 1500 rpm, and then stayed up, as if stuck.

Started at zero, and after truck started, It swung up slowly, instead of responding to RPM, kind of like the gas gauge.

Pushed choke back in lowering RPM . no response. revved engine, no response

Turned truck off, tac stayed up.

Disconnected plug at back of cluster. Still staying up.

Could I have plugged in in wrong? What else is one that plug, 2 wires for the light, and 2 for the tac?

I took the tac and Speedo out to repaint the needles orange while I had the cluster out, could I have messed it up somehow?
I was careful not to bang it up. It was just removing screws, taping the black part of the needle, and putting a couple coats of paint on.... then reverse to put them back in.


How does a tac work, It measures the frequency of coil signal right? Converts that to voltage to move the needle.... Could I have plugged it in backward and run the light current through it? I thought that was impossible due to the blocked pin on the plug.


Photo is with truck off and tac plug disconnected at back of cluster.

I thought reinstalling the cluster was going to be the easy part... sigh.

Is there a way to test the tac out of the truck?

Thanks,

Eric-

 

[OSS]

Maybe it’s something as simple as a stuck needle. Maybe when removing the cluster and setting it in a different orientation, the tach needle shifted a tad and got stuck.

Maybe tap it to see if you can free it.

 

[caladin]

No joy,

is there a way to take it apart and relube with fresh grease?

I bet I smeared the old dry grease around moving the needle while painting it.

 

[OSS]

There’s plenty of used FJ60 tachometers for sale on eBay

 

[caladin]

It got nice and hot in Texas, and the needle went back down.

Took it out and took off clear front, moved needle back and forth hoping to smooth out the grease.. Moved freely, But needle stuck in place when I let go.

No joy, but while I was trying to figure out how to take it apart I pulled forward on the back plate with the numbers and the needle fell freely. Click.

Pulled on back plate firmly bending it forward a hair, and now it's working fine. Guess I bent back a hair when painting needle causing it to interfere.

Thanks

 

[caladin]

Just in case it helps someone later on, I took it apart and realized that pulling on the white plastic bar that holds the front bushing released the needle. So I slightly un torqued the screws holding it to the frame at the bottom, un torquing the beam and freeing the neddle up.

Assembling it now, hoping it works in the truck.

Tac is working again!