No blower again

Questions about repairs and parts for Nordyne furnaces, air conditioners and heat pumps for manufactured homes including Intertherm, Mac and Miller brands. Click here for Nordyne parts.

Moderators: Greg, Mark

forlorn1
Posts: 9
Joined: Mon Aug 10, 2009 9:16 am

Intertherm 900759 blower unit attached on top of a coleman 7956-856 furnace.

Came home yesterday to no A/C, no blower. Set thermostat to Off and fan to ON on the t-stat. Blower won't come on. Previously unit worked fine, no problems with the t-stat.

Have had the blower motor replaced about 2 years ago by a local outfit, who said they had a hard time finding a motor for it. Replaced unit was about 2x as loud as the original, so I'm suspicious of it already.

What troubleshooting plan do I follow to figure out which component is the problem. Is there a troubleshooting guide for this?

Thanks
Jeff
User avatar
Robert
Moderator
Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Hi Jeff,


What is furnace brand name and model number ?




Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
forlorn1
Posts: 9
Joined: Mon Aug 10, 2009 9:16 am

Furnace : Coleman 7956-856

Blower above it : Intertherm 900759 (labeled Heating Cooling Blower)

External A/C heat exchanger : Intertherm Model # CNS50BCRAA 85MR04

Basically I see that the blower is comprised of a motor/fan, a large capacitor (for motor start I guess) and something in a rectangular box that looks like a florescent light ballast.

All the electrical wiring runs into a molded plastic plug into what appears to be a controller with a coleman 7900 label on it. So I suspect that is the thermostat unit.

Any troubleshooting tips welcome.

Jeff
User avatar
Robert
Moderator
Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Hi Jeff,


Is the outside a/c condensing unit running with t-stat in Cool-Auto-65* mode ?


Does the rectangular metal box on front of blower housing have two rocker switches on front of it ?

Heat-Off-Cool and Fan-Auto are the two switches if applicable ?



Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
forlorn1
Posts: 9
Joined: Mon Aug 10, 2009 9:16 am

Cool-Auto-65 does not start the outside A/C unit.

Not switches on the metal box, just a jumble of wires going in two different holes. Is that the t-stat control unit?

Jeff
User avatar
Robert
Moderator
Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Hi Jeff,


That's the a/c control box. Remove front cover and locate the transformer.


LINE - PRIMARY Side = 120vac


LOAD - SECONDARY Side = 24vac



Test it to see if you have power.




Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
forlorn1
Posts: 9
Joined: Mon Aug 10, 2009 9:16 am

Primary side of the transofmer has 120vac

0vac on the secondary side.

Does that mean the transformers gone?

Jeff
User avatar
Robert
Moderator
Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Hi Jeff,


Yes, transformer is bad.


Transformer # 2940A3541 can be seen and ordered through

PayPal from left side of page here :

http://www.mobilehomerepair.com/ColemanGas.html


Go to auto parts store and get 3amp atc type plug in fuse and install in the power wire on 24vac secondary side of transformer.


Wrap with electrical tape.

It will protect it from low voltage shorts.



Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
forlorn1
Posts: 9
Joined: Mon Aug 10, 2009 9:16 am

Will give it a try. Thanks for saving me the house call fee from the local HVAC place.

Jeff
User avatar
Robert
Moderator
Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Hi Jeff,


You're very welcome, happy to help.




Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
forlorn1
Posts: 9
Joined: Mon Aug 10, 2009 9:16 am

Finally got back to fixing this. Problem is that the transformer in the control box has 6 tabs while the one you recommended has 4.

I know 2 are line, 2 are load, and I'm assuming that the other 2 are a ?relay? that gets tripped by the t-stat.

So what part am I looking for in that case?

thanks again for your patience.

Jeff
User avatar
Robert
Moderator
Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Hi Jeff,

If you look closely, you'll see that your transformer has only 4 spades as well.


On two of them will be a double spade connector allowing two wires to be connected there.


Remove the connector with the two wires and connect the same way to new transformer.




Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
forlorn1
Posts: 9
Joined: Mon Aug 10, 2009 9:16 am

Here is the info on the transformer

184-2011-406-H
12FLA 60LRA 125VAC
8FLA 48LRA 250VAC
18A 277VAC
Coil 24V 50/60Hz
6205370

Has 6 contacts
1 and 3 are on the load(motor side)

2- Black
5- Red
4 - wire labeled Y
6 - wire labeled W
User avatar
Robert
Moderator
Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

That's a blower relay, not a transformer.



Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
forlorn1
Posts: 9
Joined: Mon Aug 10, 2009 9:16 am

I measured the voltage on the blower relay then.

with Cool set to On, Fan set to On, and t-stat at 65, I still have no voltage on contact 1 & 3 which are the wires running to the blower motor.

So is the blower relay my problem then, or is something else more likely?

Jeff
Locked
  • Similar Topics
    Replies
    Views
    Last post