Fluxuating amp gauge

[Peterferg]

I have a 98 mazda b3000 and my alternator gauge started fluxating.When I put my heater fan on it stops fluxuating.The resistor in my fan is blown so the fan is other on full or off.Now I went down a big hill and I was low on gas so my gas gauge dropped and my amp gauge went to a quarter and stayed there.I turned around and when I came up the hill and my gas gauge raised My amp gauge went back to half way.I went down and up the hill again with the same result.I then filled up with gas and tried the hill again with no problem.Any Ideas?

 

[1997XLTRollover]

That's weird. My alternator gauge in my 96 Explorer has just started acting funny this past week or 2 and then my fuel gauge started acting funky too... I was just going to ignore it until something failed or I felt like dealing with it. I tested my alternator and it's charging ok so I wasn't too worried. I just don't drive my truck too far and I keep an eye on it. I'm definitely interested to know what you find.