On the Yamaha Rhino when the is an "E" on the dash it means the dash needs to be replaced. I guess it happens when you turn the key on while it is on the battery charger and to many volts go to the gauge.
Thats the engine coolant temp mode check it first thing in the morning
it should be close to outside temp then start the RZR should climb
to about 210 the fan should come on then drop to about 195