how do i relight my baxi boiler pilot light ? baxi solo 3 50 pf?

P.F. means power flue. This means your boiler has an auto-ignition system that brings the pilot on and switches the gas off every cycle.
You can't relight it yourself unless an overheat or lockout reset needs to be pressed.
It should tell you how to do this in your instruction book.
If you don't have one go to Baxi's website and download for your model.
If it's not a reset problem you'll have to get someone in,because of the gas regulations.

T.h.s
June 2007