Blower running nonstop, no heat


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Old 10-14-09, 04:56 PM
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Question Tempstar 5000 - blower running nonstop, no heat

I've got a Tempstar 5000 (Model NTC5050BEA1) that is, I'm guessing, 10-15 years old. It stopped working correctly at the very end of last winter, but I'm just getting around to working on it.

Unless I breaker it down, the main blower runs continuously and nothing else is going on. The induction blower doesn't start, nor does the burner, obviously. Thermostat (round Honeywell) appears normal, reads 12VAC across the two wires coming into it. Adjusting thermostat has no effect. I believe the proper sequence should be induction fan, burner, blower - but right now it's just blower and nothing else.

I've jiggled all the wires and looked for anything obvious. Everything appears in reasonable condition. If, when breakered up, I push the panel safety switch on I hear a relay immediately kick on and the fan starts. At least I assume it's a relay - it's a small black piece at the top of the wiring/electronics box attached to the blower. This piece has, if I recall correctly, 4 wires coming off the top of it and three wires off the bottom, and a label saying something about "do not change blower speed here" or something like that - sorry I didn't write it down and can't remember exactly. And the furnace is a pain to get to.

Poking around on this forum and the web it seems it could be a "faulty fan limit control switch" or a "stuck fan switch", but I haven't figured out yet exactly where these are or how to test them.

Some pics below if they work.

Any advice would be greatly appreciated.
-Matt


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Last edited by bigmatt; 10-14-09 at 06:22 PM. Reason: pics removed for better formatting, better title
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Old 10-14-09, 07:06 PM
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Fan stays on

To have the fan come on after in break in power is normal. For the fan to stay on for more than 5 minutes or so is not.
If you have a multimeter, test each of the little switches (each with 2 red wires) on the top, bottom, & side of the burner box. Each should show continuity. If one or more does not, it means that switch is open which it should not be. They are safety switches which are supposed to trip if they get too hot.
 
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Old 10-14-09, 08:23 PM
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Originally Posted by Grady
To have the fan come on after in break in power is normal.
If I remember correctly, back when it was working properly the fan normally did not come on after a break in power - it only came on after the burner fired. I will test the safety switches on the burner box, though. I guess you're saying that if they were tripped/faulty then the fan would blow constantly.

thanks
 
 

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