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Pete, Electronic Engineer
Category: Home Improvement
Satisfied Customers: 17346
Experience:  Over 16 years of experience installing and repairing electronics.
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Liftmaster LA 400 Wire burn-though question. Alright here it

Customer Question

Liftmaster LA 400 Wire burn-though question. Alright here it goes. We have two LA 400 gate openers at our home they were purchased in May of 2014. After a little over two years of working perfectly one of them stopped working and it turned out to be the wire connecting one of the 12V batteries to the control board had burned through the plastic connector at the control board. I replaced the wire and it worked for about a week and the same thing happened. I decided to replace the battery and it worked for about a day and then the wire connecting the other 12V battery burned through the plastic connector to the control board.
Now, I had exhausted my limited knowledge of gate operators and after talking with Liftmaster, they recommended to replace the control board. I called out a gate tech to replace the control board so I wouldn't mess it up. The tech came out and measured the readings. The battery output with the old control board was ~27V which he said was causing the burn through since it was more than the 24V of the two batteries. The tech also checked the transformer which was showing the proper 36V. He replaced the control board and the battery reading was a steady 27V. He then called Liftmaster to find out why it was putting out too many volts (I found out later that 27V is in the normal range) and if they had heard of the burn through problem before. Sadly they were befuddled as well. They sent it up the chain of command, but no one could give us an answer. Now, of course the tech recommends that we replace the unit with a brand new one. However, I do not want to spend big money to replace the unit if it's gonna happen again to the new one, compounded by the fact that about two months later the other LA400 did the exact same thing. I've tried getting an electrician out here, but none were familiar with the gate operator. My question is, do you have any idea as to what the problem could be?
Submitted: 10 months ago.
Category: Home Improvement
Expert:  Pete replied 10 months ago.

Hi, I'm Pete. Welcome to JustAnswer! I'm reviewing your question now, and will post back with your reply ASAP.

Expert:  Pete replied 10 months ago.

What gauge is the wire?

High voltage alone will not cause a wire to burn - there has to be a large current draw, possibly from a short somewhere.

This could be due to a fault in the unit or damaged wiring somewhere.

Customer: replied 10 months ago.
Hi Pete, although not labeled it appears to be a 12 gauge wire. I thought it may be a short somewhere, but the tech couldn't find it and the confusion is added too by the other unit on the other side of the house doing the same thing. Could it be something in the house electric wiring causing the problem? I added pictures of the control board and the burn through from the battery connector if that helps.
Expert:  Pete replied 10 months ago.

First, you should test the wire for discontinuity. Any continuity will indicate a short.

Customer: replied 10 months ago.
Ok, I verified that the outlets turn off when I trip the breaker. Both units are on different breakers, so I'm assuming a short in both would be highly unlikely. My multi-meter broke, so I'm gonna have to get another one tonight to verify.
Expert:  Pete replied 10 months ago.

Ok, let me know how it goes...

Customer: replied 10 months ago.
Alright, I confirmed that there is 0 voltage with breakers tripped and the volts were steady at 124v when on. Now, I would like to ask you about the 12V - 7amp batteries. Is there any way they could burn through the wire themselves? The reason I ask is that when the tech left he didn't connect the battery harness to the control board, however when I just checked them, the harness was burned through on one of them.

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