Hello everyone,

I have a (2006 ford f250 5.4L V8 XLT).
This is the problem with my instrument panel. When I turn on my heater or defrost for about a 30 min drive the RMP cluster needle will drop down too zero. I do not lose power just the needle drop to zero. When i turn off the truck it will rest itself but again only when I turn on the heat this happens. Does anyone have an idea where I should look for or look at.

thanks,