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Old 01-16-2011, 05:54 PM   #1
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Inducer Motor doesn't shut off, why?


Here's the history of my problem...

I have a gas furnace. The filter was about 30 days old yesturday, so I changed it... just like I always change it.

This morning, I wake up, furnace isn't running. Hmm...

I've fixed my furnace before, taken it apart several times in the past for a thourough cleaning, no problems. So, I dive in, to investigate.

The fault code seemed to indicate that the Camstat L59-3BA switch went bad. The house was very cold, o, I jumped it out of the circuit and the furnace fired up just fine. I watched the furnace run for a while, everything was fine, except the Inducer motor never shut off.

I've got a Camstat L59-3BA switch on order, for about $40. Should have it in a day or two, I hope. In the mean time, I'm running the furnace enough to keep the house above 65 degrees.

My assumption is the camstat switch basically monitors the temp in the heat exchanger box, makes sure it doesn't get too hot. right?

The problem is, the inducer motor never shuts down during the heating cycle. I understand it should run for the first minute or two, but once the blower starts running, I believe the inducer should eventually shut off.

Any idea why the inducer motor doesn't shutdown during the heating cycle?

Once I put the new camstat in, should the problem go away? Is my jumper causing the problem?

Please help - I'd hate to have to call a service guy.

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Old 01-16-2011, 05:58 PM   #2
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Inducer Motor doesn't shut off, why?


The inducer should run for the entire call for heat.

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Old 01-16-2011, 06:04 PM   #3
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Inducer Motor doesn't shut off, why?


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The inducer should run for the entire call for heat.

Seriously? I would have sworn the inducer motor shut off at some point during the heat cycle...
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Old 01-16-2011, 06:13 PM   #4
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Inducer Motor doesn't shut off, why?


Nope. If the inducer shuts off in the middle of a cycle then the flames will roll out the front of the furnace.
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Old 01-16-2011, 06:20 PM   #5
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Inducer Motor doesn't shut off, why?


What brand and model # is the furnace. The only furnace where the inducer motor (purge blower) shuts off is a Lennox Pulse.
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Old 01-16-2011, 06:31 PM   #6
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Inducer Motor doesn't shut off, why?


It's a Bryant Furnace... was new in 1998.

Makes sense about the flame roll-out. Seems like a lot of wasted heat going up the pipe though....

I think this is the second time that Camstat switch has gone bad. I should buy two of them!

I've got a jumper wire on it now, to fool the control board. The furnace is running, but I don't have the "safety" right now.

I'm pretty proud of not having to call a service guy - I've not called one in more than ten years. I've had to repair virtually every appliance in my house (except my Fridge) at least twice in the last ten years. Some of the repairs were pretty major. Seems like my furnace always acts up on a Sunday.
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Old 01-16-2011, 06:44 PM   #7
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Inducer Motor doesn't shut off, why?


It is a draft inducer fan. That furnace cannot naturally create a draft thru it to allow the fumes to leave and to bring in enough air for combustion. No heat is being wasted.
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Old 01-16-2011, 06:55 PM   #8
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Inducer Motor doesn't shut off, why?


I wouldn't leave that limit jumpered, too great of a fire risk.

My last call Friday was to replace a blower motor. The limit had been jumpered on that furnace so the heat would run. The evap coil pan had melted and the house smelled like burning wood when I arrived. Pretty sure they were about as close to coming home to ashes as it gets.
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Old 01-16-2011, 06:56 PM   #9
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Inducer Motor doesn't shut off, why?


Thanks for the help guys!
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Old 01-16-2011, 06:59 PM   #10
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Inducer Motor doesn't shut off, why?


After you replace.I would make sure that you have enough air flow & that, the furnace isn't cycling on limit durning operation & you think it's cycling at the T.stat. Easy to tell with v.m. Hard to believe that these limits are just failing
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Old 01-16-2011, 07:09 PM   #11
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Inducer Motor doesn't shut off, why?


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After you replace.I would make sure that you have enough air flow & that, the furnace isn't cycling on limit durning operation & you think it's cycling at the T.stat. Easy to tell with v.m. Hard to believe that these limits are just failing
Might be an airflow problem, I agree. The wife has a cat... I don't have a cat... the wife has a cat. The thing sheds like crazy - drives my allergies nuts, and the hair clogs the a-coil. I change the filter a lot. Normally about every 20 days, but sometimes I forget, and it goes out to 30 or 40 days.

I take the furnace apart, down to a sheet metal box, and clean the a-coil every two to three years.... I was planning on doing it in the fall 2010, but didn't get around to it.

I'd love to install a larger blower, motor, etc.... but... that's for another day. If I ever install a new furnace in this house....
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Old 01-16-2011, 08:06 PM   #12
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Inducer Motor doesn't shut off, why?


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It's a Bryant Furnace... was new in 1998.

Makes sense about the flame roll-out. Seems like a lot of wasted heat going up the pipe though....

I think this is the second time that Camstat switch has gone bad. I should buy two of them!

I've got a jumper wire on it now, to fool the control board. The furnace is running, but I don't have the "safety" right now.

I'm pretty proud of not having to call a service guy - I've not called one in more than ten years. I've had to repair virtually every appliance in my house (except my Fridge) at least twice in the last ten years. Some of the repairs were pretty major. Seems like my furnace always acts up on a Sunday.
This is what scares me about this site. OP is proud he didn't have to call a service tech and jumped a safety interlock but yet he doesn't know the inducer fan must run during the entire heat cycle which is as basic as you can get. Sorry if I am offending anyone here, but this is plain freaking scary.
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Old 01-16-2011, 08:34 PM   #13
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Inducer Motor doesn't shut off, why?


Yah but it is the REAL world and we cannot stop people from DIY or doing it to themselves. It is a DIY forum.
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Old 01-16-2011, 09:03 PM   #14
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Inducer Motor doesn't shut off, why?


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Originally Posted by artbuc View Post
This is what scares me about this site. OP is proud he didn't have to call a service tech and jumped a safety interlock but yet he doesn't know the inducer fan must run during the entire heat cycle which is as basic as you can get. Sorry if I am offending anyone here, but this is plain freaking scary.
That's the point of the forums, helping folks to safely diagnose and repair equiptment. Keep in mind the limit was jumpered before asking questions so without a site like this it would likely still be in place.
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Old 01-16-2011, 09:15 PM   #15
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Inducer Motor doesn't shut off, why?


When you clean the "A" coil make sure you check inside the fins to get all the fir out. You may need to chemical clean the coil. Brushing and vac may not be enough.
Check for build up of fir in the blower wheel If the scoops build up with fir and dust it will reduce air flow and could cause the limit to trip.

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