Blown megafuse or what? after jumpstart..

moneypit

Original poster
Member
Dec 7, 2011
214
My daughter calls..truck won't crank, she gets a jump but not on batt. but fuse relay center-aux studs "as shown". truck starts but now missing int.lamps,wipers and other stuff...I quickly probed fuses-OK. I did also put a new batt. in..neg.had been helicoiled? it was shot. I also figured what the hay...might as well do the ign. switch while were at it. all seems well except for the circuits from the jump start?? any ideas? Thanks!
 

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STLtrailbSS

Member
Dec 4, 2011
1,617
Hopefully Roadie can chime in he had a write up on the OS. Although I have never had this happen it has been discussed its known as the Mega fuse. That 125amp fuse shown usually spells for bad news when jumped.
 

Shdwdrgn

Member
Dec 4, 2011
568
I really don't understand this. I kept seeing it mentioned over on the OS as well, and the absurdity just baffles me. The battery is right there... what genius puts the jumper cables on some unknown wires rather than the battery terminals which are just inches away and easily accessible?
 

Blckshdw

Moderator
Nov 20, 2011
10,697
Tampa Bay Area, FL
:duh: The megafuse (the 125A fuse between those 2 studs) is blown. Replace that, tell your daughter to never get a jump from those studs again, and all will be fine.
 

djthumper

Administrator
Nov 20, 2011
14,956
North Las Vegas
Blckshdw said:
:duh: The megafuse (the 125A fuse between those 2 studs) is blown. Replace that, tell your daughter to never get a jump from those studs again, and all will be fine.

:iagree: Sounds like Carlton knows first hand. :wink:
 

Blckshdw

Moderator
Nov 20, 2011
10,697
Tampa Bay Area, FL
djthumper said:
:iagree: Sounds like Carlton knows first hand. :wink:

Second hand actually :raspberry:

That, and I've seen those countless posts on the OS about it. :hopeless:
 

Me007gold

Member
Nov 20, 2011
1,106
AAA gave me a jump on those posts a few months ago, didn't realize it until after wards, as I was in the truck trying to crank it over. It fried my IP cluster. I agree with others, check your Mega fuse
 

MAY03LT

Member
Nov 18, 2011
3,422
Delmarva
moneypit said:
Yea Thanks, I do remember reading something about that...have to check?

You may have seen a video on it:cool:

Shdwdrgn said:
I really don't understand this. I kept seeing it mentioned over on the OS as well, and the absurdity just baffles me. The battery is right there... what genius puts the jumper cables on some unknown wires rather than the battery terminals which are just inches away and easily accessible?

With certain types of jumper cable clamps, its hard to get a good bite on the little dinky gm side terminal bolts. So I can see why someone who didn't know any better would use the mega fuse stud instead.
 
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moneypit

Original poster
Member
Dec 7, 2011
214
Thanks everyone, I went to parts store since dealer closed and got a temp. 175a all they had-works good, then next week I'll replace with 125a and use the 175a for a spare. Yes it's amazing just how naive college kids can be these days........ We're off for a testdrive now but all should be good after todays work.....
 

Mooseman

Moderator
Dec 4, 2011
25,599
Ottawa, ON
There are some vehicles (like our Montana), you can't get to the battery and there is a post, similar to our mega-fuse posts, which is used for jump starting. You just have to know to not use these for jump starting. Maybe just stick a label there instructing to not use these for the times you are not there getting the jump.
 

moneypit

Original poster
Member
Dec 7, 2011
214
Mooseman said:
There are some vehicles (like our Montana), you can't get to the battery and there is a post, similar to our mega-fuse posts, which is used for jump starting. You just have to know to not use these for jump starting. Maybe just stick a label there instructing to not use these for the times you are not there getting the jump.
Exactly...Yea I use to have a 2000 Olds Silhouette that had the additional post for jumping.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
The problem was made worse by the IDIOT designers who put RED and BLACK on those two megafuse terminals, and they BOTH should have been RED.

That, and folks who never read the Owner's Manual, and AAA who hires goofballs, and good Samaritans who give jumps without clues, etc., etc.
 
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Chickenhawk

Member
Dec 6, 2011
782
Owners Manuals. Good reading. Page 5-44 on my 04; page 432 on my 07:

"The other end of the negative (−) cable doesn’t go to the dead battery. It goes to a heavy, unpainted metal engine part on the vehicle with the dead battery. In the L6 engine, the remote negative (−) terminal is located on the front engine lift bracket and is marked GND. In the V8 engine, the remote negative (–) terminal is located on the accessory drive bracket and is marked GND."

Everyone. List your hood. Find the bracket. Read the "GND" clearly marked on it. Show it to your spouses and your sons/daughters.

Trust me; the day you have a battery explode in your face and feel your skin begin to burn off within seconds, you will ALWAYS treat batteries with a lot more respect.

Thankfully, the mechanic took the brunt of the explosion and there was a tire test tank within three steps of where we were. That tire test tank had the dirtiest, grungiest most foul water I had ever seen in my life. We didn't care. It saved us both from further damage, and was the most welcome water in the world.

Now, just for fun, take a look around your own shop or workplace. Do you ever work with materials that may require an emergency eye wash station or an emergency shower? Can you get to it quickly with your eyes closed?
 

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