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Dr. Hamman
Dr. Hamman, Chevy Technician
Category: Chevy
Satisfied Customers: 5866
Experience:  30 Years Experience repairing, customizing, and building chevys.
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Chevrolet Avalanche 1500 Z71 2wd: i have a 2007 chevy avalanche

Resolved Question:

i have a 2007 chevy avalanche lt z71 fully loaded and i had a wierd electrical problem first my battery died after jumping it off i noticed my turn signals, hazards, light switch,push button for tow haul and emergency brake light fail to work replaced battery same problem took it to a dealer and after a 2000 dollar repair cost they could not find the source top that off i was renting a vehicle for the 4 weeks it was in the shop im outta of cash and need assistance anything
Submitted: 1 year ago.
Category: Chevy
Expert:  Dr. Hamman replied 1 year ago.

Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you. Also keep in mind I don't know if you are a pro or a novice, so feel free to add any additional info at any time.



Hey I am an electrical specialist and I will try to help you out. As far as the dealership, you got hosed, I would consider suing them, 2K that is too severe. My shop takes on a lot of weird electrical/electronic problems so we see a lot of tough ones. We also bail out local dealerships all the time when they get in too deep. That being said these problems can be tough to spot. There is a way to test and track just about any electrical/electronic problems but most dealerships just don’t have the electronic skills, I see this all the time. A lot of these problems are better suited for an actual electronics tech, that is the problem.

Tell me a few things, what is still not working, did they fix anything at all

Do you think the battery failure was related to the other failure, or coincidence. You might have seen something that ties them together.

Get as detailed as you can about what failed and when, then what was done, and what is working now, and especially if you have seen strange signs, like devices working strangely, or coming on when they shouldn’t.

BotXXXXX XXXXXne is I am not sure I can help you without being able to work on it, so I want to be up front about that. Still I might be able to help, or at least point you in the right direction. So let me know the details, and lets see what we can do.



I do not get paid for my work unless you rate at 3 to 5 Smiley Faces or Stars, a bonus is always greatly appreciated. If the answer is not clear, let me know what additional help you need, and I will be happy to assist you further.


Customer: replied 1 year ago.

the dealership unplugged the on star module and it did nothing i told them to put it back together and i will fix it myself,ok with that being said the only problems prior to the dead battery was driver seat power controls needed several wiggles before it worked almost like low voltage and the back passenger door lock has a mind of its on sometimes it works sometimes it doesnt on a few occassions it would be unlocked and when you went to get out it would suddenly lock leaving the door still closed but not shut completely as far as all of the problems now no warnings at all the truck has always sounded like it has a weak battery when i crank it and this is the 3rd battery in 2 years now down to the current problems the battery has a 12 volt drain on it turn signals do not work wipers do hazards doesnt work and the tow haul button doesnt seem to work as the light doesnt come on when pressed emergency brake light doesnt come on when it is pressed as well however when turning the key on these lights work so i know they aren't blown the head light switch has no affect on the lights i am an electrician by trade and pretty knowledgeable in the household to industrial field i have meters test lights and a pretty wide assortment of electtrical tools so maybe with your help i can at least locate the drain i just need a good starting point oh i almost forgot i feel like the 2 main harnesses in the fuse panel under the hood each containing 70 something wires is the culprit from my random test there is a 12awg red wire that when connected seem to have a draw

Expert:  Dr. Hamman replied 1 year ago.

Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you. Also keep in mind I don't know if you are a pro or a novice, so feel free to add any additional info at any time.



You need to start off by getting to the "dead " devices and see if there is power to them. If you have worked with AC a lot DC can be a little strange. It sounds like you might have more than one problem. Honestly at this point we have no way to tell. The thing to keep in mind on DC systems that you don’t see on AC is, DC systems almost always have one wire to power a device, with some exceptions, like electric window motors. The body of the vehicle is the conductor on the negative side for most circuits. Just remember a power wire and ground, is all that is needed in a DC circuit. Another thing is: because automotive wiring is so complex, and interconnected if a circuit looses a ground, the power will back feed through any other circuit it can. Electronics techs work with this all the time when repairing circuit boards, but in the automotive industry I have it isn’t hardly ever understood, virtually no mechanics knew about this problem. It is called GF (ground feedback). You need to look out for this one, because I suspect it might be at least part of your problem. When GF is present, some devices will not work, and they will be getting power. They have lost their ground connection, and are feeding power back through other circuits, remember electricity takes the easiest path, this can take it places it shouldn’t go. GF can make devices come on that shouldn’t be on, and when GF backfeeds through a device that shouldn’t be on it will normally do screwy things.

You HAVE to get a good electrical schematic if you are going to take this one on, it isn’t optional, or you will be chasing your tail. When you get a schematic you need to make a list of all the devices/systems that are not working, and then start tracing them on the schematic. What you are looking for is common ground, or power feeds that the malfunctioning devices have in common. Because I suspect GF, I would go to and clean all the chassis grounds especially the ones connected to the devices that acting up. I like to clean the terminals with a wire brush or sand paper, and solder the terminal to the wire where it grounds. The terminal can loose electrical connection where it crimps to the wire. If you want to use a test to check the connection there is a test called voltage drop can spot this problem, I use it a lot on DC circuits, I can walk you through it if you haven’t dealt with it before. The schematics will show you the ground points. You might consider subscribing to Mitchell on line, it is a service manual, and they have the best electronic schematics in the industry.


Check power to malfunctioning circuits

Check/clean the grounds, this can work miracles, well almost.

Don’t assume a circuit has power if the idiot lights come on with the ignition on, because sometimes an electronic module will be testing the idiot light function, that is independent from actual system function.


Keep an eye out for a group of circuits/devices/systems that are controlled by a module that are not working. Always go to the power and ground of any control module if there is a module involved in a failure. You have to use voltage drop tests to get an accurate readings here. Voltage drop tests spot high resistance connections, these can cause low power and GF. Nothing picks up on a bad connect like a voltage drop test. I can point you at a good video, A LINK HERE, a basic video HERE. The first video gets a lot deeper, the second is so much easier to understand. I would watch both. Watch the basic video first, and watch it again to clear your head again after watching the more complex vid.
Go over all of this and if you have any more questions at all, I am here to help. Good luck with it, have a great day, and Thanks for using Just Answer.


I do not get paid for my work unless you rate at 3 to 5 Smiley Faces or Stars, a bonus is always greatly appreciated. If the answer is not clear, let me know what additional help you need, and I will be happy to assist you further.


Dr. Hamman, Chevy Technician
Category: Chevy
Satisfied Customers: 5866
Experience: 30 Years Experience repairing, customizing, and building chevys.
Dr. Hamman and 7 other Chevy Specialists are ready to help you
Customer: replied 1 year ago.

just checked a wire on my parking brake i can't seem to figure the assembly out the wire has 12 volts on it and it feeds 12 volts through frame there is a coil spring behind the brake assembly and it looks like it is not correct to me the wire is green and hard to trace it goes to the back of the truck is this wire that clips on the brass i'm gonna call it a switch due to the two seperate pieces of brass that opens and closes when pedal is depressed or released suppose to open and close a circuit if so it is defective traced the wire not the problem but still curious if the coil spring is suppose to well the piece that sticks out to keep the spring tight is suppose to be going to the brass what i call switch it looks like there is an indention where the piece of spring is suppose to sit help i have 3 different manuals and still no diagram

Customer: replied 1 year ago.


i will continue to tip but i have another question on the fuse box under the hood there are two studs exposed closest to head lights that have voltage kinda threw me a loop so i checked each of the harnesses that plug in the under side and all but one has a verified ground to frame however the one that does has a black and purple wire that have continuity between them but not to frame so far all solid black and purple wires have continuity to ground anywhere i have tested anything to this i don't know i left it unplugged and plugged in the rest of the harnesses and the studs had no voltage (i disconnect the battery prior to any plugging or unplugging) the studs are different sizes and colors one is larger and stainless the other is about 1/4"and black are they for another battery because there is a spot right beside the fuse box and if so shouldn't one be a ground

Expert:  Dr. Hamman replied 1 year ago.
I havent been on line, I saw your questions just now. I am on for a few hours throught the day today, I will check into your addational questions.
Expert:  Dr. Hamman replied 1 year ago.

GM commonly makes studs "hot" by the under hood fuse box. They do this so the battery power can be tapped into for adding accessories, it also gives a battery connection for testing, and charging the battery away from the battery. Battery’s put off hydrogen gas (explosive) so to be text book correct you shouldn’t make sparks around the battery, that is another reason they do it.

Anyway I would check out that black W/purple wire with no ground. You need to find it on the schematic, and see if it is ground wire. I don’t have a schematic on this one, it is about 70 pages from my source, I would have to buy it, I am trying to find one on line, it would help me to help you. If that black W/purple wire is supposed to be grounded and it isn’t, it can possibly cause a lot of problems, including GF. It isn’t safe to just ground it unless you can ID it. I don’t like surprises, especially the ones that billow smoke, so absolutely ID it before you try to ground it. I haven’t found a diagram of the parking brake that would answer the spring question you had. GM doesn’t want to break down and show how to repair a lot of smaller parts, they just want to sell whole assembly’s. When that happens they ignore little repair details.

Dr. Hamman, Chevy Technician
Category: Chevy
Satisfied Customers: 5866
Experience: 30 Years Experience repairing, customizing, and building chevys.
Dr. Hamman and 7 other Chevy Specialists are ready to help you

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