I was wondering what procedures I need to use to check this and find out why it does this. Could it be a relay or the switch itself in the cab

Thanks

 

Going to depend on what year your truck is.

 

2001 Ford ranger 3.0

 

No relays

Head light power is hard wired from Main Light switch to Multi-function switch(turn signal stalk) and then out to the head lights

Battery---(fuse)----Main light switch--------------Multi-function switch---------------------------------------------head lights--------ground

Main head light switch can fail, but generally just stops working, not on and off, but could happen
Multi-function switch is something that is used a lot, so can wear out, that would be my first stop

 

Do you think I should just replace the main head light switch and turn signal bright selector, without getting to much into it?

 

I would replace just one, your choice, and then see