'88 Camry headlights dim

The left low-beam headlight started to dim, and a couple of weeks later the right low-beam went out. Both sides worked somewhat on high beam. I thought the bulbs were bad, so I replaced both of them but the problem is still there. The battery is being charged just fine and the car starts easily. The dash lights and tail lights are behaving normally.

Is it a grounding problem? Is there a relay which is going bad?

Thanks for your help!

Sounds like high resistance caused by corrosion in a connection. Were the headlamp sockets clean? Shake any accessable wires. How about the fuse contacts? There's one relay in the system, probably in the fuse box on the right side of the engine compartment. Pull it out and check the contacts. Reseating it a few times might do it. If there's another identicle relay on the panel swap them. If you jiggle the combo switch on the steering column, does it effect the lights? Don't know where the ground is. Worth tracking it down though. Buy electrical contact cleaner or use alcohol to clean. Let us know the fix