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Q: LBEC / MBEC 50 Amp Buss Fuse on 2004 Chevrolet Avalanche 1500

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This fuse constantly blows. wehn a new fuse is in the battery is drained. any known problem / solution?
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I'm having the SAME problem! haha But I can't find the short-to-ground that others are finding. I'm probably not looking at the right spot. Any pointers?
I had the same problem. MBEC 1 50A fuse blowing. Intermittently. Power seats became in-op and also both front and rear passenger windows would not go up. I found an Orange wire routing from the Underhood Fuse Block, where MBEC 1 is located, to the Center Instrument Panel Fuse Block which is located underneath the instrument panel, near your left foot, to the left of the steering column. The Orange wire was chaffed and rubbing against the bracket as it enters the Center Instrument Panel Fuse Block, causing a short to ground. Look there, you may find the problem.
Thanks for posting, I had the exact same thing on my 2008 silverado 4x4. Found problem thanks to your post.
The MBEC fuse feeds the right door and power seat circuit breakers which are located in the relay center on the firewall near the break pedal. You can try installing a new fuse AFTER pulling the circuit breakers. If the fuse still blows the problem is between the outside fuse box and the inside relay center. If the fuse does not blow then reinstall the circuit breakers one at a time and see what happens. If there is a fault in one of the circuits feed by the breakers they will trip to protect the circuit, they can however let enough current flow to blow the MBEC fuse. Be careful, if one of the circuit breakers is tripping it will be VERY HOT to the touch. I would suspect a shorted power feed wire under the drivers seat could be causing the problem on your Chevrolet Avalanche.
Hey guys I know this post is old, however I had the same problem in my 2003 Tahoe and it was an orange wire coming from the under hood fuse block to the one right next to the parking break. The wire was rubbing on metal underneath the end of the carpet. This was causing a dead short to the 50A MBEC fuse under hood for passenger windows, power & heated seats. Pulled wires out a little, taped and repositioned them. Thanks so much for this information, keep sharing !!
Found it and fixed it! Had to pull up the tip of the carpet a little bit under where the park brake hits. Turns out it grounded out on a sharp metal bracket under the carpet after all.
I found the short by buying a couple of the 50A fuses for the MBEC 1 location. BEFORE putting the huge fuse in, I pulled both the 30A circuit breaker and 25A circuit breaker controlling the power seats and windows, respectively. (As stated by Russ)
These fuses are found just to the left of the brake pedal on the floor. There is a plastic nut that screws off so the black cover can be removed. Now you have access to the two circuit breakers.
At this point, I now place the 50A in the MBEC 1 location. It doesn't blow. I then go to the floor and place the 25A window circuit breaker right back. Notice the windows work again. As I placed the 30A seat circuit breaker back, I made sure it was dark. As I placed the circuit breaker on the terminals, I see a glow just beneath the carpet. This is how I found the short.
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