HVAC furnace blower fan capacitor question(s)

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TSPORT

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Hello all. A few weeks ago I noticed the blower fan on my furnace was not running but the compressor was running outside and air was cold at furnace. I tested the capacitor for the blower fan and it was way out of spec. so I replaced it and everything was fine. The one I replaced was original to the unit, 25 years old. Replacement capacitor = Capcom 27L570. Same specs as old one. Noticed this morning the blower not working again but compressor running and air cold at furnace blowing out the seams because not being circulated. I just tested the replacement capacitor. Spec says 5uf = +/- 6%.
It's measuring 4.57. This is over 6% out of spec. but not by much. Do you think this is enough to cause the blower motor not to start? Note: The blower fan spins freely by hand with no noise. If the capacitor is bad again, thoughts on what could be causing it to fail in such a short period of time? Logical next step for diag.?

The local HVAC parts house does not stock the capacitor so I will have to order.
I am a capable DIYer but will call in a professional for further diag. if beyond my comfort zone. The unit is a Carrier WeatherMaker 9200 gas furnace, circa 1997.
Thanks!! - Steve
 

John Gayewski

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Over heat from over current would be one cause of a cap going bad. Have you tested the fan motor?
 

TSPORT

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Over heat from over current would be one cause of a cap going bad. Have you tested the fan motor?
John, no I have not. I put the existing capacitor back in after testing and it's working now. Fan motor runs fine, no noises or binding. I have a decent VOM but am not familiar with the test procedure for the fan. If it is not overly complicated and you care to share or point me where to find it (the procedure) I will check it. I suspect the issue will occur again in the near future. Thanks - Steve
 

Fitter30

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If a supply house doesn't stock a 5 mfd cap its not a supply house. That has to be one of the most common size. Need a clamp on amp meter and volt ohm meter. Was the motor hot? Could have a internal overload opening. Holiday weekend just change it. 25 years old every time motor stops and compressor doesn't load drops to O% and compressor pressure drop into freezing pressures that aren't good for it. Caps can be within 10%. When buying a aftermarket motor because i doubt carrier will have one plus it would cost three times don't go by hp use name plate amps. If old motor amps is 4.1 new motor 4.0 buy the next larger size motor. Might also have to buy a belly band mount for the new motor. Take the old motor with u. Motor and appliance supply houses would carry motors and caps.
 

TSPORT

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If a supply house doesn't stock a 5 mfd cap its not a supply house. That has to be one of the most common size. Need a clamp on amp meter and volt ohm meter. Was the motor hot? Could have a internal overload opening. Holiday weekend just change it. 25 years old every time motor stops and compressor doesn't load drops to O% and compressor pressure drop into freezing pressures that aren't good for it. Caps can be within 10%. When buying a aftermarket motor because i doubt carrier will have one plus it would cost three times don't go by hp use name plate amps. If old motor amps is 4.1 new motor 4.0 buy the next larger size motor. Might also have to buy a belly band mount for the new motor. Take the old motor with u. Motor and appliance supply houses would carry motors and caps.
Thanks for the reply. Update on issue: Last night I noticed the blower was working but the air flow out the registers was almost non-existent (earlier last night the air flow was fine). Air blowing hard out between top of furnace and base of where evap. housing is.
I shut off the A/C and just ran fan full time. Large pool of water on floor later. I suspect the evaporator is freezing up blocking the air flow. Getting over my head now. Local HVAC tech coming out to check over for me.
Evap. does not appear blocked w/ dirt and filter is clean. I'll see what he says.
 

Fitter30

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Might want to consider a whole new system. Price of the refrigerant 22, the possible shape of the evaporator coil condensate pan, the age of the furnace and ac. Most companies don't even want to work on the older refrigerant systems.
 

TSPORT

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Might want to consider a whole new system. Price of the refrigerant 22, the possible shape of the evaporator coil condensate pan, the age of the furnace and ac. Most companies don't even want to work on the older refrigerant systems.
Service tech just finished. System was 4 lbs low. Evap. core was freezing up blocking air flow. Yes, the R22 was very pricey but the system is 25 years old now and other than cleaning the filter and the capacitor I just replaced I've never had any issues. Rolling the dice for a few more years on the system. Service visit today a small fraction of a new system. Thanks again for the input! Happy 4th!
 

John Gayewski

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Service tech just finished. System was 4 lbs low. Evap. core was freezing up blocking air flow. Yes, the R22 was very pricey but the system is 25 years old now and other than cleaning the filter and the capacitor I just replaced I've never had any issues. Rolling the dice for a few more years on the system. Service visit today a small fraction of a new system. Thanks again for the input! Happy 4th!
If your refrigerant is low then there's a leak. This will happen again and you'll pay to fill it again, or pay to have someone find the leak. They'll fix it and another one will pop up. Your past your due date.

I just went through this dance. Except when my cap went out I limped along as it was end of summer last year. This year when I started freezing up I knew I was low and decided to skip the nickel (actually probably a thousand dollars) wasting and replaced everything except the furnace.

I bought everything and ran everything and had an hvac guy fill the new system and startup. Saved a good amount and have cold air.
 

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"If your refrigerant is low then there's a leak. This will happen again and you'll pay to fill it again, or pay to have someone find the leak. They'll fix it and another one will pop up. Your past your due date."
Understood. If I can get through the summer I'll be happy. New system not in the budget for the remainder of this year. Not something I would be doing myself. Was told roughly $8-$10K for new furnace/AC set-up. Will have to do my homework first.
 
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