Day Time Running Lights - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Already Gone** · 05-13-2014, 06:10 PM

My 1999 Tahoe came from the factory with daytime running lights. Its a California truck which I imported into Canada when I bought it. Daytime running lights automatically come on at I believe 1/3 of their normal power as soon as the engine starts. That works as it should. When I put my headlight switch on the headlights do not get brighter, just have the same brightness as the daytime running lights. My high beams work as they should. My question is, does anyone know if my daytime running light module is pooched or my headlight switch is pooched or any other idea would be appreciated. I'm thinking the headlight switch is pooched...

Cape Codder · 05-13-2014, 11:42 PM

My daytime running lights are the same brightness as the low beams lights. At least they were till I pulled the fuse.

400sbctruck · 05-15-2014, 09:43 PM

I just looked at mine(97) and it does appear to be roughly the same output with a slight nod to the switch ON position.

Got me to thinking...increased amperage to the bulb does not necessarily mean increased output. The load(bulb) is simply a resistor (whose inefficiency produces heat and light) in the circuit and amperage pulled is limited more by this than the amperage capability of the DTRL.

Double power doesnt mean double perceived output. Imagine a cheap harbor freight light and then imagine the same light with 5 times the batteries powering it. Probably be indecipherably different if you blinked between them.

Bulb Condition and bulb Selection affect the circuit just as much as anything, i
Would be inclined to start there possibly.

Just an educated guess, but I was expelled from the "good" school and my "education" on this matter may be somewhat lacking.

I may have come up with a new fix to the DTRL situation-you can switch OFF or ON the function of the lights by using a switch connected to the E-brake.

I discovered the DTRL deactivates with the brake slightly depressed and flew with the idea.

Cape Codder · 05-16-2014, 08:01 AM

12 volts is 12 volts. for it to be dimmer that headlamp mode it would need additional resister on the DTRL mode. I disabled mine as I can now flash my headlights to a passing truck or someone I want to let go in traffic. With the DTRL enabled I had to turn headlamps on and then flash high beams. My truck is the W/T model with seal beams and might be different than the composite light set up.

05-13-2014, 06:10 PM	#1
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,231	Day Time Running Lights My 1999 Tahoe came from the factory with daytime running lights. Its a California truck which I imported into Canada when I bought it. Daytime running lights automatically come on at I believe 1/3 of their normal power as soon as the engine starts. That works as it should. When I put my headlight switch on the headlights do not get brighter, just have the same brightness as the daytime running lights. My high beams work as they should. My question is, does anyone know if my daytime running light module is pooched or my headlight switch is pooched or any other idea would be appreciated. I'm thinking the headlight switch is pooched... __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " In the end, we only regret the chances we didnt take " " Time is the only currency we spend without knowing the balance, use it wisely ." ..

05-13-2014, 11:42 PM	#2
Cape Codder Registered User Join Date: May 2013 Location: Centerville,Ma. Posts: 1,224	Re: Day Time Running Lights My daytime running lights are the same brightness as the low beams lights. At least they were till I pulled the fuse.

05-15-2014, 09:43 PM	#3
400sbctruck Registered User Join Date: Dec 2013 Location: Jackson,tn Posts: 70	Re: Day Time Running Lights I just looked at mine(97) and it does appear to be roughly the same output with a slight nod to the switch ON position. Got me to thinking...increased amperage to the bulb does not necessarily mean increased output. The load(bulb) is simply a resistor (whose inefficiency produces heat and light) in the circuit and amperage pulled is limited more by this than the amperage capability of the DTRL. Double power doesnt mean double perceived output. Imagine a cheap harbor freight light and then imagine the same light with 5 times the batteries powering it. Probably be indecipherably different if you blinked between them. Bulb Condition and bulb Selection affect the circuit just as much as anything, i Would be inclined to start there possibly. Just an educated guess, but I was expelled from the "good" school and my "education" on this matter may be somewhat lacking. I may have come up with a new fix to the DTRL situation-you can switch OFF or ON the function of the lights by using a switch connected to the E-brake. I discovered the DTRL deactivates with the brake slightly depressed and flew with the idea. Last edited by 400sbctruck; 05-15-2014 at 09:49 PM.

05-16-2014, 08:01 AM	#4
Cape Codder Registered User Join Date: May 2013 Location: Centerville,Ma. Posts: 1,224	Re: Day Time Running Lights 12 volts is 12 volts. for it to be dimmer that headlamp mode it would need additional resister on the DTRL mode. I disabled mine as I can now flash my headlights to a passing truck or someone I want to let go in traffic. With the DTRL enabled I had to turn headlamps on and then flash high beams. My truck is the W/T model with seal beams and might be different than the composite light set up.



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