Hi guys, long time no posts, busy being a grand dad. Anyway had old Red out the other day and found out I had no low beams. Bulbs are fine and come on with the high beams, but not by themselves, Ideas?

 

Mark

and there was no mods done since the last time they worked?  

Nothing

Multifunction switch has failed. The contact wore out on the lo beam side.

Great, was kinda thinking that way and ordered one from the parts house.

Thank you

 

Mark

Just remember headlight are backwards. Take notice the headlights are powered positive on the common contact of the bulb. Then the hi and lo are on the ground leg.

Multifunction function switch replaced, still no low beams. Next suggestion? This is a 4 headlight truck, with all 4 on when on high.

 

 

Mark

Is it a factory 4 bulb system (Sport Package) or a modified 4 bulb system (after market)?

 

- John

Modified, LMC truck w/relays. worked fine until parked this spring due to fuel prices and no need to move livestock.

 

Mark

Since it has been modified, you are on your own here.  I would verify whether the relays are using positive or negative switching (both on the coil part of the relay as well as the switch part of the relay).  Then troubleshoot the lighting circuit from there.

 

- John

On my own, wonderful, that's why I came here for help. Facts are the system worked fine until sitting for 6 months, the low beam bulbs are on when the high beams are on, therefore the bulbs are good. What remains is why the low beams are not getting power when on the low setting. Any help other than "your on your own" would be appreciated .

 

Mark

Does your sport system with upgraded harness use dual filament bulbs for low beam? I believe the 9007 are dual filament so you’d still have the low bulbs working with high beams engaged if just the low beam filament went out. 
 

If it’s not that, does your kit power the bulbs from the battery (off a relay?) I’d check that and make sure your connections are good, and check the connectors at the relays.

 

I have the Daniel Stern kit, that’s where I’d start, assuming yours is similar. 

With low beams on check with a voltmeter if there is battery power to the blub. 

If no, trace wire for open circuit or check for a bad fuse. 

If yes, then check with an ohm meter if there is continuity between the blub and ground.    

1 hour ago, Scarecrow said:

On my own, wonderful, that's why I came here for help

 

Saying that you are "on your own" was a poor choice of words on my part.  I apologize for that.  However, the forum will need information regarding how the your headlight relays and bulbs are wired since your current headlight wiring is not likely to match the FSM wiring diagram.  Also, if you let the forum know your skill set, then the forum can ask the right questions and help get this figured out. 

 

On 11/16/2022 at 12:46 PM, Scarecrow said:

Bulbs are fine and come on with the high beams, but not by themselves,

 

It is possible, although not likely, that both low beam filaments are burnt out.  You don't want to skip this step.  While you are checking, identify the bulbs - that will help with troubleshooting.

 

- John