Both DRLs stopped working, only one high beam works

[cgreer00]

Any ideas what would cause this? Neither DRL is lit now, and when I go to high beam only one high beam comes on. Last night I flicked to my high beams and they both came on for a brief second before one of them burnt out. The only thing I have done recently is install a bt-45 TOY bluetooth adapter as well as replace my cabin air filters.

I believe that the high beams and DRLs use the same bulb, just with a lower voltage for DRL. So why would the DRL not come on at all, but the high beam still work?

 

[ClassyJalopy]

I had a similar experience last year. My issue was caused by the severely compromised headlight wiring right where it plugs in to the headlights.
I'd start with checking the fuses, then bulbs and then eventually the DRL resistor.

 

[cgreer00]

I'm wondering if one bulb goes bad if it messes up the circuit/resistance some and then neither DRL will light up? Fuses are good. I guess the relay is good..it is hard to tell by just looking at it. I will replace the bulb and see what happens.

 

[MongooseGA]

We could swap. Mine only work in DRL mode, no longer in high beam.

I'm pretty sure my issue stems from submerging the truck.

 

[Rebus Knebus]

I'm wondering if one bulb goes bad if it messes up the circuit/resistance some and then neither DRL will light up? Fuses are good. I guess the relay is good..it is hard to tell by just looking at it. I will replace the bulb and see what happens.

The high beam bulbs are connected in series when used as DRL, but powered independently when used as high beams. So if one bulb burns out then no DRL.

 

[cgreer00]

Just to update this for future readers, yes the dead bulb was the culprit. Put in a new one and everything is back to normal.