Medium and Heavy Trucks

Have truck repair questions? Ask an Expert

Connect one-on-one with {0} who will answer your question

GMC c7500 no dim lights, cannot locate the drl module.

Customer Question
GMC c7500 no dim...

GMC c7500 no dim lights, cannot locate the drl module

Mechanic's Assistant: Just to clarify, what are the exact lights you're talking about?

Headlamps

Mechanic's Assistant: What is the model/year of your GMC?

2000 gmc c7500

Mechanic's Assistant: Are you fixing your vehicle yourself? What have you tried so far?

Yes, I have no power going to the dimmer switch, which shows me that may be a drl module in the system..

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Just trying to figure it out so I don’t drive around with my brights on.

Submitted: 4 years ago.Category: Medium and Heavy Trucks
Show More
Show Less
Ask Your Own Medium and Heavy Trucks Question
Answered in 18 minutes by:
10/25/2018
Technician: Wayne Crawford, Shop Owner replied 4 years ago
Wayne Crawford
Wayne Crawford, Shop Owner
Category: Medium and Heavy Trucks
Satisfied Customers: 4,382
Experience: General Repair Shop Owner
Verified

Hello. My name is ***** ***** I will be helping you today.

Lets start with how exactly the switches work.

Headlights Circuit Description

The HEADLAMP fuse supplies voltage to the headlamp switch at all times through CKT 1042 (RED). The headlamp switch includes a self-resetting circuit breaker. The circuit breaker opens if the headlamps draw too much current. When the circuit breaker opens, the breaker interrupts the current flow. If there is no current flow, the circuit breaker cools off. The circuit breaker then resets automatically.

When the headlamp switch is in the HEAD position, voltage directs to the headlamp dimmer switch and the daytime running lights (DRL) control module. The headlamp dimmer switch directs voltage to either the low beam or the high beam headlamps depending on the position of the switch. The daytime running lights (DRL) control module receives the voltage at terminal D as a headlamps ON signal, which disables DRL operation if the ignition switch is in the RUN position, the BULB TEST or the START positions.

If the headlamp switch is in the HEAD position and the headlamp dimmer switch is in the LO position, voltage flows through the normally closed contacts of the daytime running light relay to the right and the left low beam headlamps. G101 constantly grounds the headlamps on diesel engines. G111 constantly grounds the headlamps on gasoline engines.

If the headlamp switch is in the HEAD position and the headlamp dimmer switch is in the HI position, voltage directs to the right and the left high beam headlamps. Voltage also directs to the (blue) high beam indicator lamp in the instrument cluster. G101 constantly grounds the headlamps and the high beam indicator lamp on diesel engines. G111 constantly grounds the headlampsand the high beam indicator lamp on gasoline engines.

Now you say you have no voltage to the dimmer. That comes from the switch. Have you checked voltage at the switch?

Ask Your Own Medium and Heavy Trucks Question
Customer reply replied 4 years ago
I have power going to the dimmer switch on the double yellow terminal. Yes I have power at the main switch...
Technician: Wayne Crawford, Shop Owner replied 4 years ago

OK I am including the R&R on the module. That will show you where it is for testing. Its behind the gauge cluster.

Ask Your Own Medium and Heavy Trucks Question
Was this answer helpful?

How JustAnswer works

step-image
Describe your issueThe assistant will guide you
step-image
Chat 1:1 with a technicianLicensed Experts are available 24/7
step-image
100% satisfaction guaranteeGet all the answers you need
Ask Daniel Wilson Your Own Question
Daniel Wilson
Daniel Wilson
Daniel Wilson
Category: Medium and Heavy Trucks
Satisfied Customers: 6,195
6,195 Satisfied Customers
Experience: Owner at DJ Wilson

Daniel Wilson is online now

Related Medium and Heavy Trucks Questions
Does the 2012 Peterbilt 389K truck come equipped from
Hello Andy, Does the 2012 Peterbilt 389K truck come equipped from factory with automatic daytime running lights that come on when the engine is on and the headlight switch is off? If so, are the DRL p… read more
Ramon Capellan
Ramon Capellan
owner / operator
Auto Mechanics
26 satisfied customers
2006 Mack chn613 no headlights or lights. No power going to
the lights will work from the flash to pass and DRL relay… read more
Mike Mcmillan
Mike Mcmillan
Triage Tech/Shop Foreman
Associates
608 satisfied customers
Much does this cost for question and answer. What will it
Having cold start problem changed fuel module , checked injectors , bleed air -primed , have firm prime, full battery, replaced lines leaking or possibly … read more
Andy
Andy
truck /coach technician
Vocational, Technical or Trade School
214 satisfied customers
Have a 1999 freightliner century with a dashlight issue...
Hello have a 1999 freightliner century with a dashlight issue... When i turn on my headlights my dash lights go out, and when i move the headlight switch all the way down to turn on just the markers t… read more
Mike Mcmillan
Mike Mcmillan
Triage Tech/Shop Foreman
Associates
608 satisfied customers
Got a mitsu fuso fe 180 2007, the issue is that when
got a mitsu fuso fe(###) ###-####, the issue is that when starting the engine the running light is on but after 5 - 10mins runnig the light goes off , after 2 - 3 hrs moving sometimes the just sudden … read more
Mike Mcmillan
Mike Mcmillan
Triage Tech/Shop Foreman
Associates
608 satisfied customers
I have a 2006 npr Isuzu the head lights doesn't work and
Hi I have a 2006 npr Isuzu the head lights doesn't work and when I switch to high beams is a buzzing noise on the passenger side so we replace that module but still doesn't work … read more
Mike Mcmillan
Mike Mcmillan
Triage Tech/Shop Foreman
Associates
608 satisfied customers
Looking for the fuse for my flights on my 2001 classic xl.
Looking for the fuse for my flights on my 2001 classic xl … read more
Jeremy
Jeremy
Certified Truck/Bus Technician
Associate Degree
2,756 satisfied customers
Problems with Volvo headlights. High beam indicator stays
problems with Volvo headlights JA: What's the make/model/year of your truck? Engine type? Customer: high beam indicator stays on JA: Are you fixing your truck yourself? What have you tried so far? Cus… read more
Mike Mcmillan
Mike Mcmillan
Triage Tech/Shop Foreman
Associates
608 satisfied customers
2009 GMC Topkick, 6.6 Duramax. Clearance lights and
2009 GMC Topkick, 6.6 Duramax. Clearance lights and headlights (high beam) will not shut off. Need to disconnect battery. … read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
6,195 satisfied customers
My 1999 gmc c7500 dump truck the abs light flashes 3 times
my 1999 gmc c7500 dump truck the abs light flashes 3 times when you turn the key on. then it stays on after truck starts … read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
6,195 satisfied customers
I have 98 FL80 h/lite trouble need relay/fuse locations, not
Hi I'm Tom I have 98 FL80 h/lite trouble need relay/fuse locations … read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
6,195 satisfied customers
Bright lights come on on driver side, on bright, on dim only
bright lights come on on driver side, on bright, on dim only one on pass side changed headlights, headlight power port, fuse block engine compartment , dimmer switch and headlight switch.… read more
][\][iCk0411
][\][iCk0411
Fleet Warranty Manager
Vocational, Technical or Trade School
5 satisfied customers
On a 99 379 short hood, I just bought, the headlights (4) are
On a 99 379 short hood, I just bought, the headlights (4) are all on and the dimmer switch on the turn signal switch won't dim. It just clicks as you pull it toward you. The bright light indicator is … read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
6,195 satisfied customers
2007 IH 4300 1HMMAAL27H486569. Headlamps will not come on by
2007 IH 4300 1HMMAAL27H486569. Headlamps will not come on by the switch. Only the low beams come on when you release the parking brake. You can flash the high beams anytime but they will not stay on. … read more
Andy
Andy
truck /coach technician
Vocational, Technical or Trade School
214 satisfied customers
I have 2007 379 installed grand general head lights and when
I have 2007 379 installed grand general head lights and when I turn on brights the lights go out how do I fix it… read more
Daniel Wilson
Daniel Wilson
Auto Mechanics 1&2/diesel mech
6,195 satisfied customers
i have a 2004 thomas school bus, 5.9 auto air 72 pass
i have a 2004 thomas school bus, 5.9 cum auto air 72 pass bus The problem is when dim head lights to bright they will come on as switch starts to switch then go back to dim lights, Can hold dimmer swi… read more
Jeremy
Jeremy
Certified Truck/Bus Technician
Associate Degree
2,756 satisfied customers
i have a2006 gmc vin 6f414775 brake lites very dim good ground
i have a2006 gmc vin 6f414775 brake lites very dim good ground and 7.6 volts to positive any clues… read more
Wayne
Wayne
Journeyman
Vocational, Technical or Trade Scho
5,115 satisfied customers
Jeremy..same bus, 2004 Thomas model 590. Relay fixed the marker
Jeremy..same bus, 2004 Thomas model 590. Relay fixed the marker light situation, but now the high beams will not stay on. They were working. Now there is just a "Flash-to-Pass" when you try to engage … read more
Jeremy
Jeremy
Certified Truck/Bus Technician
Associate Degree
2,756 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here.

DianeDallas, TX

< Previous | Next >

Meet the Experts:

Daniel Wilson

Daniel Wilson

6,195 satisfied customers

Owner at DJ Wilson

Cat Man

Cat Man

Cat Engine Expert

5,353 satisfied customers

I am ASE Master Truck Certified.

Wayne

Wayne

Journeyman

5,115 satisfied customers

worked on, Gmc, Macks, Freight liner,Mercedes Benz,,Ford, sterling

Jeremy

Jeremy

Certified Truck/Bus Technician

2,756 satisfied customers

ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, Network Engineer specializing in CAN faults, Aftertertreatment, and vehicle communications

Curtis B.

Curtis B.

Technician

1,947 satisfied customers

Technician turned service manager on multiple lines of trucks and engines, used in industry.

cumminsdr

cumminsdr

Mechanic

1,886 satisfied customers

All types of Cummins applications

Chris (aka-Moose)

Chris (aka-Moose)

Technician

641 satisfied customers

24 years of experience diagnosing & repairing

< Previous | Next >

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x