Xantrex 458 trouble

I have a Xantrex 458 converter/inverter 2000 watt. It recently quit working and now has a fault light that says over temperature. This unit is not hot. This is in a 2004 phaeton and is the converter is original. I called tiffin and they told me to disconnect all the connection plus and minus and remote and leave it off 20-30 minutes. I was told if this did not reset this fault code it was probably something internal to the charger. This did not help. Even when I leave all of the wires disconnected and put 110 volt power to the charger the over temp fault comes on the front of the charger. I have the Xantrex out of the motorhome and have replaced it with a temporary backup converter ( not an inverter) that will get me by while I work on the Zantrex. Any suggestions on where to start before I ship it off somewhere to be repaired and is there some sort of ongoing problems with these Xantrex units so I should just buy a new unit altogether?. I have it on the work bench and am ready to open it up.

Thanks for any suggestions or help to point me in the right direction

Ken