Votage drop when coolant warms up-

[quickster45]

Thought maybe glow plug controller prob, still might be but thinking maybe something else going on now. My voltage gage in the truck bounces back and forth when the glow plugs do the afterglow, but stops if the truck is cold. But once the coolant warms up, the needle on the gauge starts bouncing back and forth again. Could this be coming from another sensor, making the voltage jump? Is engine temp and glow plug controller connected anyway, or could this be something totally different? I'm totally confused on this one. thanks

 

[fuzzy1626]

Can you hear the controller clicking as the needle moves?

 

[quickster45]

no can't hear it. that's why I'm starting to think it may be something else. But what?

 

[fuzzy1626]

What year truck?

 

[quickster45]

sorry 91 f350 7.3 just went out and tried starting it again. I can hear the clicking in there with all the noise. It's constant, but erratic. fast then slows down, then fast clicking again. And it doesn't stop