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Problem with Carrier 58MXA furnace...everything works, furnace won't come on...

Problem with Carrier 58MXA furnace...everything works, furnace won't come on...


  #1  
Old 01-31-10, 11:30 AM
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Problem with Carrier 58MXA furnace...everything works, furnace won't come on...

Hi, and thanks for reading. My furnace (Carrier 58MXA) stopped working last night. As mentioned it the title, everything seems to be working. I jumped the COM terminal to the test terminal and ran a component test. Surface ignitor came on, blowers came on, the test ran fine. I have no flashing error code currently. I have a Honeywell digital thermostat and I can hear the call for heat going through to the furnace. It goes from silent to a low hum when a call for heat is initiated. However, once the call for heat goes through, nothing happens, and the hum persists (I believe the hum is normal?). This just started last night, and I've been reading about resetting the limit switch and flame rollout switch. If no one has a suggestion on what could be wrong, could you at least point out where the flame rollout switch and limit switch is located and how to reset them manually. I can't find anything through google(images) and nothing is listed in my manual.

Thanks again for reading and much appreciation for any suggestions.

~Chipley
 
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Old 01-31-10, 11:42 AM
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Just ran another test...

I am now getting a fast flash error code after running a component test indicating the polarity is reversed? I ran upstairs to google something, went back downstairs to the furnace, smelled something funny and realized that the blower motor was extremely hot. Would this be a symptom of the polarity being reversed, and if so, how do I correct this.

Thanks again,
~Chipley
 
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Old 01-31-10, 01:00 PM
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Old 01-31-10, 01:01 PM
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You say blowers run. Do they? The both of them?: Inducer and house circulation blower?

Open compartments to find hum. (After opening the smaller bloweer compartment door, you have to hold in the safety switch to get furnace to run.) Let us know. If not from either of these motors, likely the transformer. But it does sound like blower is culprit. Could be something as simple as bearings lost lubrication(sometimes just oiling can restore motor back to easy spinning in due time/done it!, IF it is a motor you can oil) or a lock up due to a bad capacitor (only a $10 part, external part DIY replaceable). Could be the motor too. Do not believe any reversed wires with motor can cause motor symptoms.
 
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Old 01-31-10, 01:22 PM
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Thanks for your reply ecman51', and thanks for the pdf link, SeattlePioneer. The blowers are working fine. The reversed polarity symptom was because I had put the fuse in backwards after taking it out to check it. woops. I quickly realized my mistake once the fuse blew. I just got back from Home Depot with a new 3 amp fuse, replaced it, and everything seems to be working fine, but the call for heat still won't initiate. I did another component test and all components checked out and turned on(both blowers and surface ignitor). The thermostat is indeed calling for heat, but nothing is happening.

How do I reset the limit switch? From what I've read, I need to manually reset this. I found the flame rollout switch and tried to press it, but it would not press in so I assume that means it does not need a reset.

Thanks again for replying,
~Chipley
 
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Old 01-31-10, 02:16 PM
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Ummmm. A fuse doesn't have polarity, and putting it in the "wrong" way can't cause a polarity issue.

The typical limit switch resets itself once the furnace cools off.

I would suppose the problem is somewhere else.
 
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Old 01-31-10, 02:17 PM
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hi again ecman51',

Wierd issue, but upon further inspection, you were right! It was one of the motors, the inducer motor, I believe?(the motor in the top compartment, not located with the safety switch), or is it the blower motor? The wierd issue is that when I run a component test, both the motors turn on. But when I do a call for heat, the inducer motor(?) is doing the humming that i mentioned, and you said to look for, and is turning very slowly. I sped the spin up manually by rotating the motor with my hand which caused it to finally start spinning up to speed. So, my furnace is on right now, but to say the least, that was a poor solution on my part.

You said: "Could be something as simple as bearings lost lubrication(sometimes just oiling can restore motor back to easy spinning in due time/done it!, IF it is a motor you can oil)." How can I determine if it's a motor that I can oil? I would like to re-lubricate if possible and see if that fixes the solution.

Anyways, thanks for your reply, it certainly helped me out once you pointed out that the hum was most likely coming from one of the motors.

Any other suggestions on how to fix the motor would be very much appreciated, as I would not like to replace it if I don't have to.

Finally warming up after 8 hours of cold. I have a wife and a 17month old son; it's supposed to be down to 15 degrees tonight in Baltimore, Maryland, so I'm glad we have some heat for the time being. Our upstairs is usually warm because we have radiant heat in our bathroom, but I'm glad our heat's on again temporarily, so thanks again,

~Chipley
 
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Old 01-31-10, 02:36 PM
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Sometimes, horizontally oriented inducer fan motors can be lubricated, IF there are oiling ports(one at each end, on the top). But not with vertically oriented motors.

Not positive from your post, based on your comment about the safety switch. Maybe it IS the house circulation air blower motor. With those they have the exposed squirrel cage, and can be given a spin, by hand, unlike the inducer motor, which is sealed in a closed housing. Also, the house circulation blower is more subject to heat, as it first often gets quite hot before it ever turns on! This can cause marginal bearings to freeze up from thermal expansion, only with the call for heat, but not from running just the fan.

These blower motor assemblies can easily be removed and relubed. You have to pretty much pull them out of the furnace so you can get to the inner bearing oiling port.
 

Last edited by ecman51; 01-31-10 at 02:46 PM. Reason: Come back and read/added much more
 

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