[Autotec]

Sound like you have a bad connection from the battery. I would start aT THE BATTERY to make sure the connection are OK and clean. If that check good I would start doing a voltage drop test on all battery cables. Check also for loose connection at the starter and the engine battery ground and chassic grounds. If that all check OK then remove the cover at the passager firewall you see an electrical power strip with wire running off of it, make sure that all nuts on the power strip are good.