Hi Rau, this answer makes sense to me as well and it fits in with what is happening in my UPS. I am in the Caribbean and I wanted to have this ups protect a server in a school that uses a power inverter as main backup for the school. Thing is that when there is a power outage and the inverter switches in the peak generated by its non sine wave is too much for apc and it gives me this fault; which is extremely frustrating. I thought these products were more robust.
I don't know what component inside the UPS is deffective, but what this code is saying is that samething is short circuited inside the UPS, it could be anything, but the word "clamp" reminds me of a varistor ou MOV, which is the component that clamps short when there is a voltage surge condition and comes back to its normal state, an open circuit, when the voltage surge is gone. Sometimes it clamps short for good when it is hit by a large surge or just by absorving and shunting to ground many small surges. If your UPS is running fine perhaps one varistor between neutral/ground is short circuited which won't interfere in the UPS itself, but it is a safety hazzard for the user, because it increases the risk of electrocution.
I can't tell you for sure that this is the right explanation for this error code, but I think it is something close to it.
What does F04 Clamp Short mean and what would cause it?
I found a method to clear this error and make the UPS work again. I disconnected the UPS. I then disconnected the batteries for 5 minutes. I powered it up on my work bench and it looked OK. I then uninstalled the powerchute software to make sure it would not remember that my UPS had an error code. I reinstalled the latest power chute software and all has been well.
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