I have a 1984 pace arrow Motorhome. It’* sitting on a Chevrolet P30 chassis with a 454 in it. I got it running and drove it 100 miles home with no issues whatsoever. Got home and changed tires ,Brake’*, etc. went to drive into town (5miles) and when I got in town I noticed my alternator Gaige was not working. Shut it off at the store and, we’ll it wouldn’t start. Got it jumped and made it home. Checked the alternator output at the alternator and it was putting out 34 volts. I took it off and had it tested and failed. Purchased a new one and put it on. Checked the voltage at the alternator 45volts! Blew out the bulb in my test light (duh). I took it back off and had it tested and it tested good 2 different times. I have 12 volts going to the number 2 terminal of the regulator and the charging wire goes to a battery isolator under the hood. Any help would be well appreciated. Also I guess the voltage blew out my gauge because it doesn’t seem to move anymore, just stays on 10.

Never heard of this happening on anything after the mid `60s, and even then very rare.

Not knowing a lot about this vehicle, and seeing its age, I first suspect some interesting electrical work has been done and this is causing your issue.

How long have you owned it?

Here'* where I'd start:

How many volts are you reading from the battery with the key off?

How many volts are you reading from the cigarette lighter with the key off?

How many volts on the house batteries from one end to the other?