Dim head lights

I have a Jag xj8 when i turn on my head lights its very dim, but if i hit the bright lights on all the lights are normal

please advise

sorry its a 2001 xj8

Have the headlight relay checked.

thank you

Check all the connections in the harness too.

Try a dirty or loose ground wire near the head lights on older cars this would fix it. reaching here

Try taking a couple of pieces of wire and ‘hot wiring’ one headlight low beam direct from the battery and ground the other terminal to a good chassis ground. Then turn on the low beams and see if the ‘hot wired’ bulb is brighter than the normally-connected bulb. If the high beams are OK, then the ground is probably OK, but you may have bad contacts in the relay or corroded wire connections on the relay, or a problem in the bulb out sensor. An ohm meter would be useful to track down the problem.

Another consideration - when halogen headlight bulbs first came out many years ago, they told us that they would not dim with age. They lied. New headlight bulbs are always a bit brighter than old ones, and I doubt that the difference is just from freshening up the connections at the bulb sockets as the bulbs are replaced.

Also, are your lenses clear and the reflectors clean?