Why does 1 headlight work on low beam, but both work on high beam?
Not that it really matters (I don't think anyways), but I have a 91 F-150 and got a problem. The title to the thread pretty much sums it up. Only my passenger side head light works when I have them on low beam, but when I switch to high beam both head lights work. Has anyone else had a problem like this or does anyone know how to fix it?
Those ebay retrofit HID kits are illegal. The optics of the headlight assembly are not designed for the HID bulbs. All they do is scatter the light and produce glare to oncomming drivers. This is why they are not DOT approved. Besides that the components are usually inferior.
You can find good information on improved lighting here.
The best setup is running headlight relays with new OE style lense assemblies (not crystal clear or euro junk) and a pair of brighter bulbs like GE Nighthawk (not sport), Phillips Vision Plus or Xtreme Power or Sylvania Xtravision etc. These bulbs have the same wattage but a different filiment and gas mixture.
You can get the relays from LMC. They provide full power to the bulbs and carry the load so the headlight switch doesn't have to. This keeps it from overheating, which is a fairly common problem.
I mean any of the retrofit kits that just have bulbs and ballasts to fit in the stock headlights. Its the same type of kit as what you linked to. Everyone just calls them ebay kits, because they are all over ebay.
The only way to properly retrofit HID into a vehicle that did not come with it from the factory is to replace everything except the switch on the dash. I don't think such a kit is available for our trucks.
Also, with most of those kits you only have low beams and no high beams.