When I start my truck if the heat is on the fans kick on HI. If the heat is not on it won’t. Coolent is good and checked the fan relay what else could it be?? Thanks

 

If your vents are set to blow onto the windshield in any way, the AC compressor runs to dry the air. When the AC compressor runs, the fans run. This would be normal.

https://community.cartalk.com/t/defroster-runs-ac/98909

Try blowing air just to the footwells and see if the fans turn off. If not, you may have an issue.

 

The fans run anytime A/C is selected or being used. However they should be on low speed not high speed. Are you sure they're running on high speed?

 

Yes they run on hi. And the ac/ defrost is not being used

 

What does "heat is on" mean?

Do the engine fans cycle?

Do they change operation if you enable AC?

 

Engine fan running when engine is cold ultimate and solution. Read Here