Heater fan won't turn off, just cold air.

Hello, I have a Tempstart Heater that will not turn the blower off after I turn it on from the thermostat. The fan still run even when I swith off, just cold air. The only way to shut it off is to open up the heater panel and reset the button inside the heater. It was working for the first couple of years when I bought the house. I don't think it's the vent issue. I suspected it could be a relay. Please help direct me how to replace this is the problem. Thanks in advance.
kevin
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On Feb 5, 12:22pm, snipped-for-privacy@gmail.com wrote:

Furnaces have a temp switch on the hot air plenum that controls the blower. When the air gets hot enough, it turns the blower on. When it drops below a lower limit, it turns the blower off. Usually these settings are adjustable and it's possible the low limit was set right on the edge and over time, the mechanical characteristics of the switch changed a tiny bit so it no longer cycles off. It's also possible the temp switch is shot.
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On Tue, 5 Feb 2008 09:22:27 -0800 (PST), snipped-for-privacy@gmail.com wrote:

Kevin, I hate to break it to you but if you are manually resetting a limit switch you most likely have a cracked heat exchanger. Thats why it has a manual reset on it. It is a SAFETY device. If you have to push it you HAVE to find out why. Turn it off until you can get a professional to check the integrity of the heat exchanger/s. Bubba
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