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Old 09-30-2009, 10:12 AM   #1
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We have a 36 year old furnace that we know needs replacing. However, we can afford to repair right now. The problem is a lack of output. The furnace is a 1973 Sears moncrief. We get the airflow of a gravity furnace (if that makes sense) in the main rooms. We have resorted to putting fans in front of the ducts to circulate the heat. My question is what kind of troubleshooting do we need to do to increase the airflow? We have checked the ducts for leaks and cleaned the furnace and replace the belts.

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Old 09-30-2009, 10:19 AM   #2
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What size are the ducts.
How many return ducts and registers do you have.

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Old 09-30-2009, 10:23 AM   #3
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Originally Posted by pennypincher View Post
We have a 36 year old furnace that we know needs replacing. However, we can afford to repair right now. The problem is a lack of output. The furnace is a 1973 Sears moncrief. We get the airflow of a gravity furnace (if that makes sense) in the main rooms. We have resorted to putting fans in front of the ducts to circulate the heat. My question is what kind of troubleshooting do we need to do to increase the airflow? We have checked the ducts for leaks and cleaned the furnace and replace the belts.
On the surface it would appear that your blower motor could be running too slow or possibly worn out. Has the motor ever been serviced or replaced over the last 36 yrs?

I'd get a tech. out to check things out. The thought of a furnace with inadequate airflow doesn't sound too safe. Make it clear to the tech. that you want an estimate for repair only because they'll likely try and sell you a whole new system.

By replacing the motor and servicing the blower assembly you could possibly buy some time.

I'm reluctant to recommend DIY but if you go that route be safe.

P.S. Have you changed the filter recently?
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Old 09-30-2009, 11:03 AM   #4
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ty for your quick answer, yes we have replaced the filter. I have had a furnace man in to inspect the furnace and he said that the belt needs replacing, which we did. That is all. He said everything else is fine with it. I only asked for an inspection, not a repair, but I would think he would notice anything serious?
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Old 09-30-2009, 11:27 AM   #5
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ducts are 6 inches and we have returns in every room
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Old 09-30-2009, 11:48 AM   #6
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I have had a furnace man in to inspect the furnace and he said that the belt needs replacing, which we did. That is all. He said everything else is fine with it. I only asked for an inspection, not a repair, but I would think he would notice anything serious?
Apparently not. Get someone who knows what they are doing and get it repaired.
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Old 09-30-2009, 02:17 PM   #7
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Would you know the BTU rating, or model number.
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Old 10-01-2009, 12:07 PM   #8
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Do you have an A/C coil on this furnace? If so you may want to clean it, may be plugged.

Also, check the blower motor for an adjustable sheave. If it has one and you close it up you will get more blower speed. This may also overload the motor so it is best to check the amp draw after adjustments.

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