My son and I put a new booster pump on his 87 f150. That part went great but now his pedal is a lot ighter than before which he can get used to that. The main issue is his brake lights won't come on till he really gets on the brakes, before it was basically when he touched the pedal. We put a new switch on it with same results. 45 minutes to replace the booster 3 hours fighting with the switch I am done for the night.

Thanks for any help.

 

Bleed the brakes. All 4 of them.

 

That was my first thought also but we didn't take any brake lines off the master cylinder. We just unbolted it from the booster pump and bungee corded it out of the way.

 

Any wetness about master cylinder when you removed it? If so it is bad. Or rear brake need adjustment.

 

Something's not quite lined up or adjusted right at the switch. Switch is controlled by pedal movement.

 

X2

You'll want to adjust the switch and play with it until the lights illuminate when the pedal is depressed roughly 1/4".

And I would recommend bleeding the brakes, if that doesn't firm it up at all, the master cylinder pushrod may need adjusted. If it's too short it was cause too much pedal free play.