2007 GMC Yukon Electrical system is completely dead

DENALI

MEMBER
2007 GMC YUKON
V8
AWD
AUTOMATIC
22,000 MILES

My battery died and a couple of people offered a jump start. They accidentally reversed the jumper leads when connecting to my battery ( positive to negative) when attempting to give me a jump. Now the car's electrical system is completely dead. What is wrong? Is there a master fuse or circuit breaker? If so, where?
Thank you, Jim

2 Replies

BRIAN 1

MECHANIC
1,030 POSTS

First start by checking all the fuses first, then post back and will advise from there.

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Saturday, January 31st, 2009 AT 3:45 PM

DENALI

MEMBER
2 POSTS

Here is what I found out: Thanks for replying.

When jumper cables are reversed, the alternator effectively serves as a dead short across the jumping battery. Because this draws huge amounts of current, which could start an electrical fire; vehicle manufacturers build a protective device called a fusible link into the vehicle's electrical system. The fusible link looks like a battery cable; but it usually has an identifying tag on it. It is designed to burn out and go open if too much current is drawn through the system. Sometimes that may save the alternator; but the internal diodes in the alternator are usually destroyed when jumper cables are reversed.

So the solution is to buy a new fusible link, and probably a new alternator as well. You could have the diodes in the old alternator tested before replacing it; just on the odd chance that they are still good. But be sure to not just install a fusible link and connect a good battery to the electrical system without first testing or replacing the alternator. If the alternator diodes are shorted; it will destroy the new fusible link as soon as you connect power to the system.