instrument cluster issue

[supervert]

my problem is when i turn on my lights, my tach drops from around 600 rpms to 0 rpms( wile running and at a idle ). but after a wile it will gradually work its way back to normal. i haven't messed with it yet, but i am going to check all of the grounds and and the rest of the connections.

do any of you guys have a clue to what the issue is ?



truck is 89, 7.3 5spd

 

[Agnem]

Moosestang does that too some days. It is a combination of low battery voltage at idle, and weak tach sensor windings. I'm pretty sure if you replace your tach sensor, that will probably cure it.

 

[Optikalillushun]

i was also told it could be the main ground for the cluster. mine does some erratic things as well...like randomly fall to zero while driving and such.

 

[Agnem]

It could be that as well. A grounding issue will certainly affect the voltage the cluster sees.

 

[supervert]

thanks guys, that what i was kinda figuring.