On 78 F150 2wd Where is the main power buss located? I have changed the system to 1 wire Alt but still have some surge i.e. heat / ac , Headlights ect. I would like to upgrade the system to get rid of the stress on factory wiring . Tired of up and down effect on headlights and blower motor for heat and air , depending on eng. rpm . Where is the best place to purchase the headlight upgrade wiring harness or should i get a couple of relays and build my own ??

 

All of the power to the vehicle sources off the battery-side of the starter solenoid. If your headlights are flickering you may have a grounding problem. Check to make sure that you have a healthy-looking ground strap from the firewall to the engine block.

 

They don't fliker they get brighter or dimmer depending on engine RPM . I have changed all the ground straps even added a few , Also all new headlight switch , dimmer, ignition switch , and 1 wire Alt.

 

That still sounds like a regulation problem. It means the regulator isn't switching the alternator on\off quickly enough based on its increase in output when you rev the engine. How much are we talking here? A little change in brightness is unavoidable.

 

Its either a weak battery, bad regulator, alternator or you have something like a huge stereo system or auxilary lighting draging down the system. How many amps is your alternator?