First let me say I've searched and read a lot here and my truck ISN'T A 2003 and the problem ISN'T THE REAR LIGHTS (I think).

The driver side low beam doesn't work but the high beam does. I tried installing a new bulb but that didn't change anything. About a month ago the “lamp out” came on but cycling the headlight switch made it go away.

I took things apart today to test for voltage and such and the low beam was working intermittently.

The only things that came to mind were a bad ground or the headlight switch is bad? Any thoughts would be greatly appreciated. I've never had a very good grasp of electricity.

 

Might be forward control module.

Pete

 

it could also be a relay that is flaking out on you.

 

Did you look at the connector for that headlight bulb and make sure there wasn't a barbecued terminal? Quite common.

 

Thanks for all the replies.

It isn't a barbecued terminal because I saw them all when I was sticking the volt meter in them.

Is there any way to test a relay to know if this is the problem?

Also, what is the forward control module?

I was thinking of buying a new switch and putting it in there as long as they aren't too expensive.

 

there is no relay on the 04.5 both headlights are triggered with solid state components in the fcm and is not serviceable , i do not understand a lot of things with it's wiring , i have spent several days changing to led's and hid i have rewired the headlights about 5 times and fixing to change it again i think the headlight switch supplies power to a circuit in the fcm there it is monitored and sent to each headlight. the 03 is totally different than the 06, i think your 04.5 is closer to the 06 . i have not checked on the price of the fcm but if it is as high as the others now might be a good time to go hid

 

I guess my question now is: Is it possible for the headlight switch to only turn on one headlight? Or does this eliminate the switch as the source of the problem?

Since the fcm is so expensive, I'm thinking a $40 switch sounds good.