heat blower

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  #1  
Old 03-03-03, 09:41 PM
kai
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heat blower

I have a Magic Chef forced air natural gas central heating unit. Recently it does not work properly. Normally when it calls for heat, the gas is lit up, it waits for a few second then the blower motor turns on and blows the heat to the vent.
But sometime gas was lit up ok, but the blower motor did not turn on, gas was eventually out. The temperature just drop drop....

Any idea what could cause it? Any comment would be great appreciated.
 
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  #2  
Old 03-04-03, 10:19 AM
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blower

Have you turned the blower on at the tstat or at the blower control to see if the motor will run or not? If you dont know how to go into this I think best you call HVAC to look at it. You could have a bad blower motor ED
 
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Old 03-04-03, 03:42 PM
kai
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Thanks a lot, Ed. I don't know much at all about the heating system.
What is HVAC?

kai
 
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Old 03-04-03, 03:47 PM
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referring to

hvac tech (heating ventilation a/c) does the fan run in the on position?
 
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Old 03-04-03, 04:11 PM
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blower

You want to call a company that works on furnaces. Look one up in the phone book for one Ok ED
 
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Old 03-06-03, 04:24 PM
kai
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HI, hvac4u,

The fan works just fine at on position. And the problem is only at auto position and it occurs every once in a while. Could it be the thermostat problem?
Thanks.

kai
 
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Old 03-06-03, 04:36 PM
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blower

If the blower ran when you put it to ON ok. I would think that the motor is going out in the heat speed or your fan limit control is going out on you. I would say no its not the thermostat . I still think you should get some one to look at it. ED
 
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Old 03-06-03, 04:54 PM
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fan

on gas furnace is not controlled by tstat, limit or relay on board depending on age, that is where i would look
 
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Old 03-10-03, 07:15 AM
kai
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hvac4u and Ed,

Thank both of you so much. I definitely will find someone come to check it. However before that I will try to see if a new
thermostat works the trick. My thermostat is old and needs to be replaced anyway. I am going to get a programmable one. If it does not work, I will call HVAC to check it for me.
BTW, when is the best time to have furnice serviced? I usually do it before the winter every 2 years.
 
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Old 03-10-03, 04:54 PM
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I wouldn't bother with the thermostat. If the ON position of the thermostat runs the fan, your thermostat is OK. When the fan switch is on AUTO, the fan is controlled by a temperature switch on (or in) the furnace. It may be going bad. You ar eprobably better off having a tech look at it for you but why replace the thermostat if you don't have to?
 
  #11  
Old 03-12-03, 07:17 AM
kai
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Hi, KField,

Thanks a lot. I do see a thermal switch on the celling right above the furnace. I really don't know much about furnace. I thought, since I hear a click everytime right before the gas is lit up, it was the thermal switch. From what you said, it seems like the click was just from a relay? So the gas is lit up till there is enough heat to turn the thermal switch to start the fan?
I will have a tech to look at it. Thank you very much.
 
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Old 03-24-03, 08:41 AM
kai
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Hi, Ed, HVAC4U, KField,

I had a technician come to take a look at it. It seems like the
Thermal Cut-off Switch is going bad. It was an Firomatic one. I had it replaced and it costs me almost $200. Since my problem was not occuring very often, so will see if this really solve my problem.
Thanks a lot for all your help. It was great talking to you.

kai
 
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Old 03-24-03, 09:47 AM
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If the switch you had replaced was not an integral part of your furnace, you will probably be working on this one again. You seemed to be explaining a problem that was related to the blower control. If the thermal switch you had replaced was mounted on the ceiling and wired into the furnace power, it would control the whole furnace. Gas valve and all. NOT just the blower. Did your tech checkout the fan & limit control? I hope. That is where I suspected your you trouble stemmed from. If you have more trouble, give us the model of the furnace and let us see if we can get more specific.
 
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Old 03-24-03, 11:57 AM
kai
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I don't think he had checked the fan or the limit control. The cut-off thermal switch is the one that mounted on the ceilling and the one that I had repalced. Hmmm.... if this is not where the problem resides, what I am gonna do? I guess I will have to see if more problems come up. I definite will let you know if I have more troubles. I really appreciate your help.

kai
 
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Old 04-08-03, 09:30 AM
kai
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Hi, KField,

I guess you were right. My problem has not been fixed.
The pass week was bad that it occured almost everyday. I called up the technician again, he came and the funny thing is that he could not reproduce the problem. This time he did check the
controls to the fan, but he said that since he could not reproduce the problem, he could not know for sure which part is bad or going bad. He said he is pretty sure (not completely sure) it would be
the time delay relay. He said he could replace that but there might be something else wrong. I just can not let him replace it without 100% garentee that it will fix my problem, besides it will cost me another $189. So what is your opinion. Could it be soly cuased by the relay?

thanks.

kai
 
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Old 04-08-03, 12:28 PM
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Not knowing exactly what method your furnace uses to trigger the fan makes it difficult for me to tell you what the likelyhood is of a fix. If your furnace uses a time delay relay to activate the fan, it is a prime candidate for this problem. However, if it is a solid state time delay relay, it is less likely. If it is a heater type time delay, it could be the source of the problem. I think the delays are only about $30 so I don't know where the $189 comes from. This call would constitute a callback in my book. That eliminates any speial trip charge or callout fee and labor charge picks up right where it left off last week. You didn't ask them to replace the wrong part, only to repair the problem. If the furnace worked at all, why would someone blame the firomatic switch? It is a one-time device. Anyay, I would think for $89 the blower control is a good bet, for $189 it is too expensive. Just my opinion. I probably didn't help you very much but someone else will probably jump in and offer another opinion.

Ken
 
  #17  
Old 04-09-03, 07:10 AM
kai
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HI, KField,

Thank you so much. I don't know what type of the time delay relay it is, however I was able to write down what I see on the relay. I2S20 304929 H24V H25-55 C15-45 there is a little lable on the very top which I can not tell very clearly "THERN-G-DISC" ? Hope it can give you some hint on the relay type.

kai
 
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Old 04-09-03, 07:50 AM
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A therm-o-disc is a bi-metal heater type time delay and could be the cause of your trouble. The only other possible culpret would be an intermittent problem with the blower motor but turning the fan to the on position should rule that out.

I would suggest replacing the time delay. The numbers you gave us should be helpful in locating one if you plan on doing it yourself. If not, keep in mind that it is NOT an expensive part. The equivalent ones I have are in the $40-45 range.

Good luck and if you have any more questions, ask them here.

Ken
 
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Old 04-09-03, 10:07 AM
kai
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Thank you so much, KField,

Yes, I am going to replace it myself. I was searching on the internet, but could not locate the same brand and type. Could you please help me find an equivalent one? By either tell me what those number mean so I can find one on the internet by myself or just simply order from you.
Your help are greatly appreciated.

kai
 
  #20  
Old 04-09-03, 12:26 PM
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The ones in my favorite catalog are Cam-Stat brand and while I can't tell you exactly what the numbers mean, I assume that the 24v means the control circuit works on 24 volts ac. The H and C numbers are probably on and off delays in seconds. They are not critical as long as the on delay does not let your furnace overheat before starting the fan. If you look for a Johnstone supply near you ans check if they will sell to you (which I have been told they won't but have seen it happen often), their stock number is L36-824 for a control that has a 45 second turn on delay and a 75 second off delay. That should be pretty close to what you need. Adjustable ones are available but they are too expensive to be worth the money. If you can't buy from Johnstone, maybe you can find a source on the internet.

The terminals may be oriented differently, but it should be easy to figure out.

Ken
 
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