OT: Home HVAC Fan Blower

Way OT, but controls related.

I know I should find HVAC forum for this, but I am sure controls guys may have an idea:

My house central HVAC blower just quit working last night,
Only Fan problem, all other functions "look OK" as far as I can see

AC compressor turns ON, but blower motor makes noise (no spin) for 5-6 seconds and quits for another 40-50 sec shutting down compressor as well. At this point it tries again...

It looks like I will not get anyone for a few days, so I decided to look myself.

I restarted it in Fan ON mode (no AC), it started once and nothing since, same problem.
Whole thing is in the attic and hard to get in.
Visually all looking clean, incoming 120VAC is there.

So I am thinkg that 3 things can be bad:
- Capacitor
- Controller (fan control circuit)
- Motor itself (no belt)

Since it make a noise like it lost a phase, I am thinking just to replace capacitor.
Motor looks like a single phase with huge capacitor on the side and has 3 different leads for 3 different speeds, all connected to controller.
Any other ideas?

I've had to replace the capacitor on mine a couple of times, it was acting just like yours is.

Just spoke with one of AC repair guys - he will not be able to come at least intil Tuesday, but gave some BS about motor overheating - I explained to him the it was on for last 12 hours and should at least start for few seconds to get overheated. He did not like me mentioning a capacitor.

Sound like replacing just a capacitor is too small job

I vote for the cap. I had to change one out a few years back.

I think I am going to take cap out to see if I can measure it.

May be I can get one without having guy to come

OK, capacitor is in my hands now,

Measuring capacitance with DMM: 0
Measuring small capacitors I have - all show correct readings
So I can safely say - it is bad!

Now how can I find it on Sunday?
Google search returned many hits,
This is a first one
http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=591-0510&SEARCH=&ID=&DESC=97F9002

Appliance parts. Well stocked hardware store. I assume it's a run cap. Metal, oval, about 5 microfarads (MFD).
If it's round plastic, try to get a metal one. They last longer.
Edit - Looked at Allied link. That one looks good. Carry that picture to hardware/appliance store.
If you have an old AC outdoor unit, it will have one. Don't go lower than 8 MFD.

This link from Allied is exact part number I have 97F9002 10uF 370VAC rating.
Local part stores closed today.
I will call them tomorrow morning.
If not, then I will order from Allied.
It's not hot today and cold front coming tomorrow, so I can leave few days without AC

WWGraingers

Grainger Part number number 2GE79 is exactly what you are looking for. It will break the bank at six dollars 29 cents. Sounds like a deal to stay cool.

I see McMaster has it also 7602K27

I have both locally but Grainger is just 5 miles away.

Why home stuff always breaks on weekends or after 10pm weekdays?
Last year I had roof leak at 4 am...

I was HVAC man yeas ago. I only used 4?? volt caps. Sorry I can't remember the exact voltage. This will give you a greater safety factor. It will be several hours before I get to the house but when I get home I will fill in the ?? . You can go up in the voltage not down. The micofarad rated needs to be with 10% of the rated. I had a make a cap that I carried with me on service runs. It was a group of caps that I had to place jumpers between. I was about $75 but a nice troubleshooting tool.

While were at it. I have a slightly different AC problem.

I just found out my AC died. I usually don't use it unless it get very hot 90+. I have only checked the breaker and the fact the fan fill on the outside unit will not turn the blower is fine but I only get hot air. The unit is 10 or 11 years old. If the compressor motor is burned out should I bother with replacing the motor or is it time for an expensive upgrade? BTW, I have natural gas for heating but I would consider a heat pump because it could be used most of the time. Rarely does the temperature go below freezing for any length of time.

Do the ex HVAC guys have a suggestions? There would be a circuit break inside the AC unit itself would there? I would need to remove the covers.

Peter
Is the compressor running when the relay pulls in? Does the relay even pull in? FYI It is more than likely a single pole

Peter,

I have separate 2-pole breaker for outside AC unit.
Furnace(gas)including fan blower use own single phase breaker.

I remember having similar problem few years ago when 2-pole breaker tripped for some reason.

This is a first
A question asked by Peter that I can answer.

If the Compressors motor is burnt out it is time to update, but in saying that is most unlikely to be burnt out, more likely to be a starting relay fault, or starting / run capacitor, or you may have a manually resettable high pressure switch that needs reset.

Its a shame that this is probably the only question from Peter that I may have got right.