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Failed 4024 Inverter and fix
Last week I went out to the bus and found that one of my 4024 inverters had shut down. I had replaced a 300 amp T type fuse last year to fixed the same problem so that is the first place I looked. I measured the voltage at both ends of the fuse and had 28 Volts at the battery end and 6.4 volts at the inverter end. I did not think much of it since that was the same reading I had with last year’s failure and an electrian friend told me these fuses were encased in a sand like material and could leave a carbon trail that could conduct a smal amount of current.
After replacing the fuse I had the same readings so that concerned me. I removed the cable from the inverter and then that end of the cable begin reading 21 volts. While removing the fuse to check and tighten all the wiring connections I had that small spark again and I noticed that the square block on the Xantrex fuse holder that the fuse uses as it’s contact moved. When I checked further it would spin on the bolts that holds the fuse. Using a pair of pliers I tighened both of the blocks and all wires connections and replaced the fuse and the cable to the inverter and all worked great. I now suspect that may have been my issue last year and the fuse I replaced was not bad either. Just one more thing to check when working on these units.
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2 Replies
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the voltage drop across a fuse should always be near zero when measured using a voltmeter with one test lead on each end of the fuse and the power turned on and the load engaged. When measured between ground and either end of the fuse, the two voltages should be the same. Any difference would be measured in millivolts.
a voltage drop across a fuse can mean that either the fuse is bad internally, or, that the fuse holder has a bad connection that introduces a resistance.
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Routinely (annually) checking ALL battery and battery cable connections, including bus bars (if equipped), alternators, isolators, and inverter inputs, etc is STRONGLY suggested to all of our service customers, especially if the coach has the SW-series of inverters. Loose connections can become a serious issue, and even result in heat damage or fire in the worst of cases. High current, temperature extremes, plus the fact that coaches move, things vibrate, and so on, help make this something to keep up on.
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