The headlight on my FXST will go dim.. But even when it is running dim the dimmer switch still works high_beam and low_beam just too dim. Some of the time it will stay dim for quite a long time then brighten again. Both with the switch in the high_beam and low_beam position. Anyone know what is happening with this. Is it a common problem?

 

Check your battery terminals they could be getting loose. Might want to replace the bulb as well.

 

Sounds like a flat/low battery to me

Had similar symptoms on my MT-01

 

After checking the battery connections as E8USMCRET points out, the way to know for sure what's going on is by doing a voltage check of both the battery while it's running, and then at the headlight plug. That will either tell you where the problem is....or is not. If the voltage is good at the headlight plug, like around 13v while running and the headlight is dim, then it's probably the headlight itself or the headlight ground.

Diagnosing problems like this can be a process of elimination. Finding where the problem is not narrows down the list of places where it is.

 

First thing I would check is the connection at the bulb. Is it tight? Is there corrosion? Then go from there.

Cheers!

 

Had a switch grounding out on my bars one time a long time ago on a dirt and trail I had that messed with the light voltage.