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2004 chevy trailblazer_lt
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I have a 2004 Chevy Trailblazer. My buddy ran the battery down listening to the radio and my roomate had to get it jumped to get it started. I found out later that they initially tried to hook the battery cables to the red and black cables leading into the fuse box. After getting the car jumped, the car has the following electrical problems:
1. Radio will not work
2. Electric locks will not work
3. Windows will not work
4. Interior lights do not work
5. Cigarette lighter does not work
6. A/c does not work. The blower does work
7. Dash lights do not work

I checked the fuses that you can visually inspect in both places and did not see any blown fuses. Since this happened after attempting to jump the car in the wrong place, I am assuming that this is the cause of the problem.


suggestions?:thx
 

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Common, common problem because of GM's idiot decision to put a black wire on a threaded stud where it can be seen and used for jumping, except it carries 12V, not ground! The rear fuse block, under the rear seat, now has zero power.

You simply blew the 125 Amp Megafuse bolted to the studs. Not all car parts stores carry them, but I've found them in marine parts stores. Pepboys was reported to have had them on the shelf. I carry a spare tywrapped nearby.

http://forums.trailvoy.com/showthread.php?t=45959
 

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thanks for the response you solved my problem! However I pulled the fuse out and simply put it back in without replacing with a new and now everything works..does this sound right? Im sure it had to blow the fuse when they tried to jump it.
 

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thanks for the response you solved my problem! However I pulled the fuse out and simply put it back in without replacing with a new and now everything works..does this sound right? Im sure it had to blow the fuse when they tried to jump it.
Unless there was a corroded/oxidized contact holding the fuse in, I cannot imagine any way that reinstalling it would help. The body isn't flexible enough to allow a small internal open circuit to be closed again. I would go on a hunt for a spare soon so you can replace it with a known good one. The number or circuits you lose is pretty high, and includes brake lights and some running lights IIRC.

150A as a spare?:bonk:
Yep. I got mine at West Marine, and they had 100 and 150s. I'm an electrical engineer, and the upsized 150 doesn't bother me. I also sometimes run an extra 45 Amps through the megafuse to recharge a rear-area RV battery used for my Engel fridge. But I haven't blown the 125 A fuse ever, so the spare is still just sitting there.
 

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Common, common problem because of GM's idiot decision to put a black wire on a threaded stud where it can be seen and used for jumping, except it carries 12V, not ground! The rear fuse block, under the rear seat, now has zero power.

You simply blew the 125 Amp Megafuse bolted to the studs. Not all car parts stores carry them, but I've found them in marine parts stores. Pepboys was reported to have had them on the shelf. I carry a spare tywrapped nearby.

http://forums.trailvoy.com/showthread.php?t=45959








my mom the fool she is did this to my TB yesterday. The same problem occured with me, no interior lights/radio/cigg lighter power/ dash display/ rear window washer/ n i cant swith over to4WD. are you sure this is the only problem and not a short any where else? cuz if so that would be amazing cuz i dont feel like spending an arm or leg on getting it fixed.
 

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...are you sure this is the only problem...
How can anyone possibly give you a guarantee like that without using a meter on your vehicle to confirm the fuse is open? And that doesn't begin to address the question of WHY your Mom had to jump it in the first place.

If she connected the jump cables to the wrong place, then the FIRST thing to do is replace the megafuse. But there may be an underlying problem, like a dying battery, parasitic (inadvertent) current drain, wiring harness short, dead alternator, etc.

Do you have any idea why she dragged out the jump cables in the first place?

Do you or a friend have a DVM and know how to use it?
 

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it was snowing yesterday and she took my truck to use the 4wd to go out but it wouldnt start so she tried jumping it from her car to mine but apparently she hooked it up to the wrong place so she woke me up and told me what happened. so we jumped it the right way and it started but like i ssaid nothing in the interior would work. so i was just aasking if that could be the main problem and hopefully nothing else
 

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... but it wouldnt start...
The megafuse is definitely gonzo, but you may still have a bad/old battery or something else wrong. How old is the battery and has it ever been replaced? Could you have left a reading light on the night before? Was it not driven for a week? Just trying to help understand why your Mom felt the need to jump it.
 

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Why would anyone use studs that are not coming OFF of the battery in the first place?

AMAZING.

BTW,
This thread points out that perhaps I should grab a spare 150w MegaFuse...
 

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i have an aftermarket stereo with subs n amp and i was clening my car out last week while i was listening to it witht he key turned to accesorie and after about 10 minutes the car shut off n wouldnt start. so i jumped it with my dads truck and it worked fine. so then the story before bout my mom occured and iguess maybe it wouldnt start again so thats why she jumped it (wrong). im going now to get the new part so hopefully itll work and im not screwed
 

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Why would anyone use studs that are not coming OFF of the first place?
I think it's because if your battery box is still on, they're hard to clamp to? And lots of folks know about the RED/BLACK color code, and can't imagine GM would violate that by putting a FAT black wire on a stud that's carrying 12V!

The megafuse studs really should have been protected by a cover, and labeled DO NOT JUMP HERE.
 

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Since I've been a member here I've read about a couple of dozen folks who blew their megafuses and none of them reported later problems with the BCM. Good luck, and let us know what turns up after you replace the fuse.

If your mechanics have experience with trailvoy electrical systems, I'd be shocked. If only you had a meter it would be a quick confirmation that the fuse was open.
 

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no power to electrical accessories

thanks to Blitzedr6 for the answer on the megafuse problem. I replaced mine witha 150 AMP fuse available off the shelf at PepBoys. Is this OK or do I need to gat a 125Amp mega fuse?
Trailperson:):)
 

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As an electrical engineer, I would say it's OK, since that's the spare that I carry. It's just to protect the vehicle from burning up if somebody shorted the feed wire (from the stud to the rear fuse panel) to ground. What the designers didn't want to happen is a partial short (higher than zero Ohms resistance, that is) to NOT blow the fuse. You can run 100 Amps through a length of 16 AWG wire, and it turns into a 1000 Watt blow dryer element :eek: :eek: :cool:, glows red hot, starts a fire in your carpet :eek: :duh: , yet will fail to blow a 125 or 150 Amp fuse.

The wire going from the stud to the rear fuse panel is much fatter than 16 gauge, so if it shorts to ground, it will draw MORE than 125 Amps, and I'm saying from experience it will also draw more than 150 Amps and also blow your larger fuse.

In normal operation there's no difference in the circuit to put in a larger fuse than stock - it's just there for safety in case of overloads. Rare.

Tutorial: What *is* to be avoided is to put in a LARGER fuse, like 20 Amps, in a 10 Amp circuit that's ALREADY blown. That's just bad troubleshooting. Figure out where the overload is FIRST by visual inspection or clever use of a meter, then replace the fuse. A larger fuse installed on a bad circuit just invites trouble, such as starting a fire then tracing from the carbon charring where the short must have been. :nono: :no: :weird:

Clever use of a meter involves one of my favorite tricks for finding shorts. Take a rechargable battery like a NiCd. (NiMH usually will self-destruct if you short them out and create a huge current spike.) Connect the battery on the circuit that has a short to ground. The battery will (for a short time, like a few minutes) give you a 5-10 Amp current source, but with limited (1.2) voltage. Connect one end of your meter to ground. Get a safety pin or needle, and use that on the other end of the meter. Start poking into the wire insulation. Near the battery end of the wire, you'll see something close to 1V. As you move to other parts of the wire closer to the short, you'll see lower and lower voltage, like 0.4, 0.3, 0.1. The mimimum voltage on the wire will be closest to the short. If you poke into the wire on the OTHER side of the short, AWAY from the battery, the voltage will remain at its minimum, let's say 0.1V. The voltage will NOT go higher the farther away from the short you get, as long as you're on the NON-BATTERY side of the wire. Just think of the wire as a very low resistance (but continuous) resistor.

If you don't know where the wire runs from where you connected the battery, such as if it has a joint in it - just follow the wire in whatever direction gives you constantly decreasing voltage. Like following a stream downhill. Same idea.
 
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