daytime running lights - how they work?

[steve-r]

i recently installed the DSG headlight booster kit, and wow, let there be light. better yet, having hi & low beams on for "hi beams" really lights up the road.
but my DRL's aren't functioning properly anymore.
they flash once on 'crank to start', flash once when i release the e-brake, flash once when i turn off the headlights.

can someone please explain the normal operation of the DRL Module and the DRL Relay.
ie. when the DRLM detects headlights on or off, what does it do, which terminals does it detect a voltage or non-voltage condition, and which terminals does it control, what does it activate, and how does that affect the Relay. in turn how does that affect the hi-beam operation.
if i can get an explanation of what normal operation is supposed to be, then i might have a chance of solving this.

appreciate any guidance.
i've been working with DSG to shoot the problem, but no joy yet.
i have 2 gif's showing the wiring diagram of the DRL Module, Relay and lights. but i don't know how to paste them into this post. i can email them to anyone who thinks they can help.

thx in advance.

[Beedee]

Steve
dikdok@island.net
I'm working this weekend, but if I get some time I'll look at it for you and see if I can come up wit something.
Brian

[MikeC]

Steve,

When I installed the light booster I pulled my DRL fuse in the panel that is accessible when the drivers door is open.

Mike

[steve-r]

i checked the DRL fuse and it is fine.
also checked the HTR-AC fuse, also fine.
i reviewed the installation again today w. DSG and i've installed it correctly. my DRL module may be giving a bad voltage, so i'm hoping to check some voltage readings from another stock 94, then i can compare & confirm.

[a5150nut]

Steve, I think MikeC was saying to remove the fuse and the problem would go with it. But as you are in the North you are required to have your lights on. :eek:

[steve-r]

i misunderstood. yes, i'd like to do without them.
$90 for a new DRL module, and $62 for a new DRL Relay from the stealer. maybe i'd be better off pulling the fuse and installing some nice Hella driving /fog lights w. a switch instead. more light is good!

i found a fellow workmate here that has a 94 gmc gasser. same DRL wiring. he let me take some voltage readings off his DRLM & DRLR today. they are clearly different than what mine reads. so i am concluding my DRL module is not functioning properly. seems strange that before the booster install my DRL's worked fine. maybe something shorted and now its pooched. i'll do some more diagnosis this weekend and i'll post what i find. thanks.

[tom.mcinerney]

Steve, goto the thread initiated by '65-f100', "Topic: Headlight Harness Upgrade - $23" ; read the post by 'gmctd' on 03/08/'04 at 2:45 P.M.

[steve-r]

hmmm. i wonder. the DSG booster kit has a diode but it is used to bridge the low beams on when the hi beams are selected. i didn't notice any other diodes in the kit. anyone know if it has additional diode protection?

[tom.mcinerney]

Steve-Fog lamps complicate things a little. If headlamps ON or parking brake ON or ignition OFF, DRL is disabled. Basic headlamp operation consists of both LH and RH Highbeam lights connected to battery+ , in parallel. Basic DRL operation consists of (Helm 8A-104-19)"Voltage is applied through the DRL-FOG FUSE 15 and the closed contacts of the DRL Relay to the LH and RH High Beam Headlamps (now placed in a series circuit). Since the High Beam Headlamps are in series, they will burn at a lower intensity than if they were in regular High Beam operation."
It would help to know if any vehicle your wiring has the mod and functioning DRL. May need modify with extra relay to enable series/parallel stuff. I'll look at gifs if still problemmatic, mail is "tbhpmci(remove this)@yahoo.com".Try small attachments as my mail clogged.....good luck, post back.

[steve-r]

DSG Saskatoon said they installed the booster kit on a 94 Burb last week and had no problems w. DRL's. The shop foreman and I compared notes on install procedure - identical.
he took some voltage readings at various terminals on the burb's DRL module w. engine running, lights off/on, e-brake off & on. he got different results than mine.
i found a workmate here in Vcr with a 94 gasser. i took some voltage readings from his. he matches the Burb. again, mine are different.
as far as i can tell, the DRL wiring is the same regardless of diesel or gas. the burb does have one slight difference vs the pickup in terms of DRL wiring, but it is inconsequential i think.
so i have either a bad DRL relay, or a bad DRL module.
perhaps a spike referenced earlier fried something upon first test of the booster kit.
i'll email the gif's, they are small.
i'll be doing some further diagnosis this weekend. i'll post what results they got vs. what my readings are. thanks!

[MikeC]

Yes, I did say to pull the fuse. What I didn't say was that I also run with my lights, all of them, on all the time. The fuse pull just kept the lights from coming on when I had not set my parking brake.

I don't recommend running without lights, just tried to avoid an extra load when glowing and starting smile.gif

Mike

[Gapper_ca]

My DRL quit working all together.
i replaced the Diode and that fixed it. was not the relay or modual.
part # 15043231 diode $41.85 from GM dealer in Kindersley

it is a heat sync with diode hooked up.

[tom.mcinerney]

That's great, Gapper CA. I was just going to advise Steve that if a diode died it would probably signal the module to disable the DRLs. That is, one of the two diodes in the OEM wire harness. That would account for a different input to module; causing different output.

[steve-r]

ok. in the wiring diagram, i can see a diode in the braking system. it is on the tan/white line that feeds the DRL. since operation of the e-brake successully interrupts the 12v feed to the DRL on that circuit, same as my buddies 94, then i have to assume that diode is ok. if it wasn't, it would be feeding 12v to my braking system , and the brakelights would be malfunctioning.
i don't see another one.
any hints as to where it is located, and what color wire feeds it/leaves it? should be easy to test if i can find it. thx

[tom.mcinerney]

OK, Steve, i received your gifs. On the "drl with quadlamps2.gif" , a diode, 'D200' is shown between 's250' and 's252' . Three tan/white .5 sq mm circuit 33 wires connect at 's250'(one directly to ignition switch, one to the drl mod, and one to the parking brake warning switch), and one such wire runs from 's252' to 's253' where it connects to diode 201[center-right area of your 2.gif]. I agree that D200 relates to the park brake. The second, D201, seems to connect to the ABS module and the brake pressure warning switch [I'm following the wires to another page in my Helm. My wiring close, not idendical to yours...]. The DRL module has a static handling precaution.
I originally mentioned the diodes because they are somewhat vulnerable to shorts, etc. The DRL mod may be as well.
One filament of the LH & RH Hi Beams are hardwired together and to an output of the headlamp dimmer switch{OEM config}. When this is 'hot', both HiBeams lite if both wires from other sides of filaments grounded [parallel on]. The RH HiBeam wire from this 'other side of filament' is hardwire grounded to G112, RH for'd lamp ground. The left HiBeam 'other side of filament' wire is grounded via splice 's204' to I/P ground 'G200'(that's back at the instrument panel)?!, through the normally closed contacts of the DRL relay. But when the DRLs are shining, the LH HiBeam 'other side of filament' wire is energized thru the DRL relay. So when the DRL relay makes contact, it removes ground from LH HiBeam, and connects to power thru the 20A DRL fuse , [series on].
If your new wiring good, problem likely-1 module 2 relay 3 diodes 4 wire open/short. It is not clear how many diodes are in circuit(s). My Helm labels inconsistently. Sub more likely than p/u; also more likely if have foglamps.My book says D200 is "behind center portion of I/P"; D202 is in "I/P harness, approx 11cm from cruise control harness breakout"...' but 94diff harness fr '95. The books troubleshooting DOES NOT mention the diodes at all in the 11 step diagnostics of the problem 'DRL are inoperative'. Good Luck!

[steve-r]

Tom Mac, thx for the research. i suspect the drl module as well. i verified the relay is ok.
i have 12v at C4 and C5.
when i ground C2 on the relay, i get 12V at C1 and fulltime Drl's...proving the wiring is correct
so the DRL module should ground terminal G when
ignition is on, 12v at terminal C and one of:
a) e-brake is off, 12V at terminal A, or
b) lamps off, terminal D is 0V

when G is grounded properly by the module, it completes the relay circuit, opens the relay, and feeds 12V from relay C4 to C1....since C1 is now connected to my lowbeam booster relay(used to be driver side high beam, then series to passenger side), it powers on the lowbeams at a full 13.9V...voila bright DRL's.

i get 12V at C4, C5, C2 and 0V at C1, except for the initial DRL flash when key is turned on, or engine starts, or e-brake released. its like a circuit breaker kicks in and turns them off. but no fuses blow. and since my headlights are off, the circuit breaker in the headlight sw is not the culprit.

so my choices are:
-$90 Cdn for a new DRL module from GM (expensive guess_
-try to get one from the wreckers (cheaper guess)
-pull the DRL fuse, disconnect C1 from my lowbeams
and run without "automatic" DRL's

so, i pulled the fuse and disconnected, and started using my lowbeams ("manual DRL's").
i'll see what they charge for a module at the wreckers.
concern with replacing is "what caused it in the 1st place?" ..so it could happen again..ie. a mystery spike. don't need to throw good money after bad. if i spend money, i'd rather get a good set of hella driving/fog lamps or equivalent for $90.

funny...while we have the DRL "law" here, i notice lots of 1990-newer vehicles without them on, and i don't see them handing out lots of tickets for not having them on... "gee occifer, my DRL's don't work? , thats weird, musta just happened, likely a blown fuse, i'll turn my headlights on, and get it fixed right away! thanks for letting me know"

thanks all for your valued help & coaching. its not like i'm going down in defeat, rather i'm just choosing to fight a different battle for now. meanwhile, i'm enjoying night driving w. my new , much brighter lows, and my super bright ( all 4 lamps 2x55w+2x65w) highs.
those deer better lookout now!

[tom.mcinerney]

Steve, sounds like you've got it 'wired'. Regarding the part procurement, call a dealer for the part number. Then contact a TDP member/vendor in the Great Lakes region,"Dmaxallitech" , ask him for a quote on a delivered new OEM part: <tqauto@aol.com >.