[mbaas]

Model Ruud UGDA-12EA-GR 1983
The first problem was the fan would run non stop. I was told to check the t-stat & wire (ok) & then to remove the wire from the (G) termnal on the furnace. I did & the fan turned off, so I replaced the t-stat & now the burner & fan won't turn off.
Should I replace the Fan Limit Control next?

[drtom4444]

It sounds like it's wired wrong. You will get nowhere fast replacing parts without knowing if they are good or not. Why don't you get a meter and then you can do it right. I teach children to use a meter and they do well on young as eight years old, so I know it's not hard to learn. Remember: W goes to heat, G to fan relay, Y to the contactor for AC, and R supplies power to other side of these switches, and C is common on some t-stats. Common is the other side of all the previous relays. You can test the fan switch and check it. It has an on/auto switch on it to make the fan run off the t-stat built in or on all the time (manual). It could be switched on, too. If you do get one get the right length of sensor. Look at: https://dl.dropbox.com/u/8010163/How...e%20Manual.pdf
https://dl.dropbox.com/u/8010163/AC%...20Diagrams.zip