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IASM · 03-22-2021, 09:40 PM

So the rv has been parked in the garage plugged in for a year. We have been using the fridge for house overflow. I went out to get some milk and the power was down. Went through the normal troubleshooting and found the 400 amp fuse feeding 12 volt to the inverter blew. This troubles me since there was no load on the inverter not the charger section. Relatively new magnum inverter.
Has anyone had a fuse go for no reason?
My first thought is something on the horizon with the inverter.
To blow the fuse you need load and with no power being used the only load source would be internal with the inverter itself.
Thoughts?

**CountryFit** · 03-22-2021, 11:09 PM

400a is a lot. I had my 350a T fuse burned once becaue while it was charging my EV toad (135a @12v) I forgot it and started using microwave in high power (150a @12v). That was a real overload. In your case a fridge doesn't use many amps, to burn a 400a fuse it had to be short of circuit somewhere. What you can do is to do a few tests -

(1) While T fuse is removed, you can test the resistence between the fuse holder at inverter side and the battery negative terminal. If the reading isn't infinite, the inverter board is likely shot.

(2) Now if it is infinite (open), you can disconnect the output wires of the inverter, use a 10-15a or so fuse to bridge the T fuse holder and turn on inverter. If inverter starts and stays on, your inverter isn't the gremlin.

(3) Then you can focus on your 120v circuits.

Good luck!

twinboat · 03-23-2021, 06:43 AM

Stick your nose up in the inverter compartment. If it blew that fuse, its cooked and will smell burnt.

If not, check for a serious short to ground on the positive cable.

wolfe10 · 03-23-2021, 06:51 AM

Check every inch of the positive cabling from fuse to inverter.

Look for any evidence (like rodent damage) of bare wire touching any metal (ground).

OR evidence of a rodent electrocution!

IASM · 03-23-2021, 10:36 AM

Everything checks out fine. I tested all the circuits before i stuck the new fuse in. The positive cable is fully visible going to the inverter. The fuse itself looks like it has never seen heat. I am wondering if corrosion over the last 13 years caused a natural failure.