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Matthew
Matthew, HVAC Technician
Category: HVAC
Satisfied Customers: 2014
Experience:  14 years experience in the HVAC field of service, installation, Manual J & D calculations
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I have Armstrong AC, Model#SCU10B36A-3. Furnace fan kicks in

Resolved Question:

I have Armstrong AC, Model#SCU10B36A-3. Furnace fan kicks in but AC fan wont engage. Shut the system off thinking it was frozen. Checked CB - all good.
Submitted: 5 years ago.
Category: HVAC
Expert:  Matthew replied 5 years ago.

Matthew :

Hello, My name is XXXXX XXXXX I will do my best to help you today.

Matthew :

If the outdoor unit is coming on then you have one of a few things that could be wrong.

Matthew :

1. There is no high voltage to the outdoor unit due to a tripped breaker in the main homes panel.

Matthew :

2. There is no low voltage being sent to the outdoor unit due to a broken low voltage wire or because of a safety device like a condensate pump or float switch that is activated stopping power to the outdoor unit.

Matthew :

3. The duel capacitor inside the outdoor unit is blown and not giving the compressor and fan motor a jump start to get started.

Matthew :

4. The contacts inside the outdoor unit are bad and not sending voltage through them.

Matthew :

To test most of these you would need a volt meter and the ability to check and test for high voltage at these various parts.

Matthew :

sorry first sentence should have been if the outdoor unit isn't coming on and the indoor unit is.

Customer:

do you have the part number for the dual capacitor?

Matthew :

Full Size Image

Customer:

Home depot will have one

Matthew :

they are a universal part for every brand of equipment. It will have a ratting on it that reads something like 35/5 440 or 45/5 370 as long as those numbers are the same any brand capacitor will work.

Matthew :

no

Matthew :

it is a specialty part sold at wholesale supply houses or online hvac parts stores.

Customer:

Is this a common issue?

Matthew :

yes most common repair part for airconditioner

Matthew :

most often when they blow the top will be bulged and all deformed

Matthew :

Do not have to be deformed to be bad but most often it's a clear indication that it's bad.

Customer:

Anyrhing else I should check for, I did clean the vents few weeks ago

Matthew :

shouldn't have anything to do with the outdoor unit not coming on.

Matthew :

If you take a stick with the system calling for it to be on and push the fan motor and the fan then kciks on and runs you have a bad duel capacitor.

Customer:

where can I find a manual on this unit?

Matthew :

Armstrong doesn't have online manuals available they are one of the few brands that make it difficult to find any manuals or installation instructions that come with it. Even if you could get one it's not going to tell you much or be much help. With a volt meter you can find the problem in a few mins.

Customer:

I have a multimeter

Matthew :

Full Size Image

Matthew :

this is the contacts inside the outdoor unit.

Matthew :

On one end the two wires from the disconnect box on the side of the home hook up and feed 240v.

Matthew :

on the opposite end are all the wires to the condenser fan, compressor, capacitor.

Matthew :

When there is a 24v call from the thermostat the small pole with the copper points in the middle pull down and the points make contact with the metal below sending the 240v through the contacts to the other side for all the parts in the unit to energize.

Matthew :

First thing you need to do is see if the points are pulled down in a call for cooling. If they are then there is 24v to the unit. Then you need to see if htere is 240v at both ends of the contacts. If there isn't 240v at the end from the disconnect then you have a bad breaker inside, loose wire, or bad disconnect box on the side of the home.

Matthew :

If there is 240v at the supply end of the contacts but no 240v at the other end where the condenser fan and compressor wires hook up with the points pulled down then the contacts are bad.

Matthew :

If there is 240v at both ends of the contacts then the duel capacitor is bad.

Matthew :

here is one hooked up with wires.

Matthew :

Full Size Image

Customer:

Ok look like I have some work to do. I will check it out.

Matthew :

I'll check back in a bit to see what you have found

Customer:

Check the switch, it does engage with 24v. When engaged there is a hum, I tried mvong the fan burt it wont turn

Matthew :

do you hear the compressor coming on?

Matthew :

it will be a very loud harmonic rumble.

Matthew :

If the fan will not spin free and easy then your condenser motor is seized up and not running. If the compressor comes on and runs without the fan motor running then it will not take long for the compressor to overheat and shut off on internal overload. If this is what is happening then you need a new condenser fan motor and the unit needs to be left sitting for a few hours to let the compressor cool down. Sometimes you have to run a water hose over the compressor for a bit to get it to come out of internal overload.

Customer:

I managed to get the fan running using a stick, I did not hear the compressor kicking on, just the fan running. the air extracted from the fan is cool. the compressor is cool to the touch

Matthew :

If the fan starts running when you give it a kick start then it is the duel capacitor that is bad. This capacitor gives both the fan and the compressor a boost to get going at start up and then they run off the 240v power being supplied to the system. You can't give the compressor a "jump" start like you do with the fan using a stick so the compressor will never start up until the capacitor is replaced.

Customer:

I replaced the capacitor with the Turbo 200 universal and all seems to work. It may take a while as it is 91 today

Matthew :

good deal.

Matthew :

Where did you get the Turbo 200 if you don't mind me asking?

Customer:

I found a local HVAC guy that charged me double the price $100. This should be in every household or everyone should have a replacement capacitor

Matthew :

got ya. Yeah those turbo's installed go for about 225 installed once you include the service call and labor. A generic exact replacement capacitor runs for about 175 installed

Customer: AmRad Engineering Turbo200 Motor Run Capacitor

$59

Matthew :

yeah $125 if sold to you buy a service company + service call $85 plus 1/4hr labor @ 85/hr. We sell generic capacitors for about $65 they can be bought at retail or around $15. Any service industry does this the mark up on parts covers overhead.

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