1. You don't blow bulbs because of a bad ground.
2. We don't know what truck this is.
3. You can't say "wiring is all good" if you are blowing bulbs. Something is NOT "functioning well".
4. We don't know what bulbs are blowing and if they all are on a 15 amp fuse.
5. We don't know if they are dual filament bulbs and just one filament is burning out.
6. You haven't told us anything that could possible allow us to help, except to fire off a dozen causes.
7. You sure need to explain that ground wire from "the switch" you added. as in: from what/to what?
8. Assuming "the switch" means the sigstat 900. There is NO ground wire associated with this switch.
9. "It's 15 amp fused"...what is IT? What part of "IT" is fused?
So give us some info per above. Be specific on each point. No. 2, 4, 5, 7, 8 & 9. Repeat: be specific.
These questions are to save us firing off two dozen causes.
