Carrier Model 58ES080-30 HVAC blower motor will not turn off. Help?

First check to be sure the thermostat blower switch is in automatic (auto) on the thermostat. Sometimes people turn the blower switch to on instead of automatic by mistake.

Then if that is not the problem it is usually the fan relay in the furnace that gets stuck.

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Originally Posted by hvac1000

First check to be sure the thermostat blower switch is in automatic (auto) on the thermostat. Sometimes people turn the blower switch to on instead of automatic by mistake.

Then if that is not the problem it is usually the fan relay in the furnace that gets stuck.

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Wow, such a fast reply! Thanks. The thermostat blower switch is in AUTO, so it must be the fan relay. How do I find the fan relay? It it also known as a limit switch?

Usually the item is not called a limit but older furnaces have a combination control called a fan and limit control. Look on the back side of the blower door for a wiring diagram

Quote:

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Originally Posted by hvac1000

Usually the item is not called a limit but older furnaces have a combination control called a fan and limit control. Look on the back side of the blower door for a wiring diagram

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It is an older Carrier Model # 58ES080-30. If there was a wiring diagram, it's long gone. I can play around with switches inside the furnace. Would it have only two wires going to it?

That unit is from back in 1972 to 1975 and yes it is old as in very old. I would suggest you have the heat excahnger tested by a professional.

Now back to the unit

Thete are fan and limit controls like the pictures below. This could be causing your problem. Some of them also have a push-pull or turn off and on switch that could be causing the problem.

HVAC1000 is on to your culprit. Let us know if you have this control in your furnace. IF not, you may have a simple high limit (two wires on face of heat exchanger) that has failed. This would cause blower to run nonstop. I also agree about having the heat exchanger tested by a pro, as a leaky heat exchanger will cause higher temps causing this problem, and also can be deadly due to carbon monoxide entering the home through heat vents.

Now, my true thoughts,, with a furnace that old, its time to seriously start thinking about replacement. Even if it's a simple fix, your putting money into a dying horse. Just put the thing to rest. Its had a long hard life,(oh, if furnaces could talk). Good luck and please let us know how things work out. Lee.