Electric furnance wont shut off

[hawgwildtours]

My friend called and asked if i could replace her thermostat..No problem says i..WHY I ASK..she says heat wont shut off and she wants a new thermostat any way..ok..change thermostat and same problem..go back over and turn heat on and it shuts off when it gets to temp >???I think maybe sequencer is sticking so i change it..unit works fine,,shuts on and off..i leave and she calls and says its 86 degrees in house and therm is on 72 ...i go back this morning and change the fan relay since ive changed everything else,what the hell..same story,i turn unit on and its 68 in house,put therm on 70 and wait.temp goes to 71 and fan changes speeds ,runs a little bit and unit shuts off..turn therm up to 72 and same thing temp goes to 73 unit shuts down..sh just called and says its 80 in the house and we left it on 70..this is a furdown unit,kind of old,no numbers any where i can find..any ideas..thanks

[RegUS_PatOff]

furnace model number ?

[hawgwildtours]

wish i knew...unit is very old and i did not find a model number,,furdown unit mounted above bathtub...basic electric furnace with 2 stage sequencer ,fan relay ,and 2 hi temp cut offs..i think i will have her run it next time before i get there so maybe i can catch it acting up..for some reason it works fine for a while and then later on it sticks and stays on..

[applianceman18007260692]

Lets see so far you have installed a new thermostat set up for electric heat and a new sequencer. Fan speeds are changing? Electric heat is one speed and that is wide open. Must have a problem with the blower.

[hawgwildtours]

when i said fan speed was changing that was an assumption..when it reaches temp it get a little quieter and then runs a minute or two and then completly shuts down...i assumed it was changing speeds because on the wiring digram it shows high and low on the fan

[RegUS_PatOff]

can you scan & upload the wiring diagram somewhere ?

[ACtechGUY]

Check the wire between the thermostat and heater. it is possible that there is an intermittant short that keeps the heat sequencer energized. The most likely locations for this is right behind the thermostat and in the heater itself.