Gas Furnace Not working at all. HELP!

Hi all,
I need help on my house gas furnace which is not working now. The model is Carrier 58STA/STX. It’s about 6 years old. The symptoms are like the following:

Four days ago, we noticed that there was humming sound from the AC before it started. Then two days later, we could only hear the humming sound but the furnace wouldn’t start and the fan couldn’t turn on even we set it to be on. I opened the cover of the furnace and tried to see if there are any obvious things I can see but I didn’t see any. After the observation, I turned on the switch again but this time I even didn’t hear the humming sound.

The first thing I tried is to take the capacitor to the parts store asked them to check whether that’s bad. They tested the capacitor and the number only ran to 7. According to the sales person, it should be close to 7.5. So I bought a new capacitor and connected it to the gas furnace. However, nothing happens. So now it seems that no power goes into the system.
I’ve attached some photos of the units. Please help me take a look and let me know what could be wrong. Thank you very much for your help!!

 

I'm not a furnace expert but I just wanted to toss in: If you did this with the cover open then it would not have even attempted to come on. You'll need to make the switch think the cover is on to test it out with the cover open like that. Just hold it down with your thumb. Looks like the big black one upper-middle by the blower.

 

Welcome to the forums.

Make sure the capacitor is mounted so it can't short out. Put the blower door back on like Core suggested. Allow furnace to start up. If there is further problem.... look thru the sight glass on the blower door and you'll see a red LED. That will blink a trouble code if there is a startup problem.

 

All right, Here is what I did today. I mounted on the capacitor, put the cover back and then turn on the system. I recorded three videos for the LED status and put them on youtube. Here's the link to them:
Video1: video1 - YouTube
Video2: video2 - YouTube
Video3: video3 - YouTube

After the first video I actually turned off the power again and went down stairs. But when I went back and turn on the system and recorded the second Video2, the LED stayed lit and the gas furnace was able to work for about 3 minutes. It then shut down again and gave out signals shown in Video3. If I am right in counting, the error code seems to be 33.

Now what should I do next? Thanks!

 

A schematic with error code info should be glued to the access panel.

You have to look up the code.

 

I believe 33 is open limit switch. You probably fried it when the blower wasn't running. Do you have a multimeter that you can use to check continuity? The limit device may be "above" the burners (right in your case?) and it might have 2 red wires going to it. Check for continuity there. Or take it out and have that same parts place test it for you. You can jumper the two wires together as a test but do not leave the furnace running this way.

Again, I want to emphasize I am not an HVAC guy but I know how it can be waiting hours for a pro response while you're sitting there with no heat trying to troubleshoot things.

 

In the first video you had a code 12. That's a blower issue.
In the third video you had a code 33 which is limit switch issue.

You changed the capacitor but it sounds like the blower motor is defective.
Did you try spinning it by hand to see if it was frozen or binding ?

The following is what should be the manual for you unit as you did not post the complete model number.

hvacpartners.com/idc/groups/public/documents/techlit/58st-13si.pdf

 

Here is what I found on those error code:
Code 12 BLOWER ON AFTER POWER UP (115 VAC or 24 VAC) -Blower runs for 90 seconds,
if unit is powered up during a call for heat (R-W closed) or R-W opens during blower
on-delay.


Code 33. LIMIT CIRCUIT FAULT - Indicates a limit, draft safeguard, flame rollout, or blocked vent
switch (if used) is open. Blower will run for 4 minutes or until open switch remakes
whichever is longer. If open longer than 3 minutes, code changes to lockout #13.
If open less than 3 minutes status code #33 continues to flash until blower shuts off.
Flame rollout switch and BVSS require manual reset. Check for: - Restricted vent
- Proper vent sizing - Loose blower wheel. - Excessive wind
- Dirty filter or restricted duct system.
- Defective blower motor or capacitor. - Defective switch or connections.
- Inadequate combustion air supply (Flame Roll-out Switch open).


I did try to spin the motor and it didn't move smoothly. I have to constantly spin it. I'll take out the motor and check it today.

Thanks a lot for all replying!

 

Oh, I thought the blower itself was working fine after your fix. I misunderstood your earlier post. I'm glad PJMax caught that. ricewjx, I guess I would have just flipped the thermostat to fan-only after the cap swap to make sure the blower fix was working before heating her up and going through all the fuss with the codes.

If you're going to take the motor out of there, and end up having to replace it: Use emery cloth and penetrating oil on the shaft _before_ trying to pull the wheel off. If it gets stuck, do not use a very large hammer in an attempt to dislodge it. You may end up with a bent shaft or worse. Ask me how I know this.

When mine quit on me I was able to limp along for a few weeks by setting the blower to the highest possible setting and oiling the heck out of the thing. Replacement job wasn't bad at all but those motors aren't cheap.

 

Thanks. After further reading the manual. Code 12 seems to be normal during the operation. From the manual:
NOTE: If a power interruption occurs during a call for heat (W),
the control will start a 90-second blower-only ON period two
seconds after power is restored, if the thermostat is still calling for
gas heating. The red LED light will flash code 12 during the
90-second period, after which the LED will be ON continuous, as
long as no faults are detected. After the 90-second period, the
furnace will respond to the thermostat normally.

But Code 33 definitely a problem. I hope that it's just the motor got sticky and cannot spin as fas as required.

 

So you're saying the blower was spinning for a few minutes? Or was it just humming?

I hope that's not what it is. If the bearing's shot I'm not sure what you're going to do with it, unless someone here has some tricks. You can't even properly oil these newer motors. There's a whole bunch of stuff I'd rather replace than a $200 motor.

I'm still not clear from reading your posts whether you're saying the blower is spinning at all or not. Or are you not sure? That's probably tough to tell if you're at a circuit breaker panel an entire floor away. Doesn't your furnace have a disconnecting means (light switch) right near it that you could use?

 

Sorry that I was not clear. I should have recorded the second video a little longer as you can see that the burner was fired up and the heater was on a little less than 3 minutes and the system shut down with only the humming sound. During the 3 minutes running, I assume that the blower should be spinning.

 

So the burners were lit but you're just assuming the blower was on. Yes it "should" be spinning after a certain delay but it sounds like it was not. The fact that it was humming after it shut down leads me to believe it was never spinning at all. If you were standing next to the thing when the burners fired up and waited a little while (45 seconds? whatever it is on yours) then you couldn't possibly miss the sound of that blower starting.

If it was my furnace I would use the fan switch on the thermostat to activate the blower when you test it rather than overheating the furnace with each attempt. Whenever you play with it next I mean. Maybe those heat exchangers are tough but that just seems like asking for it.

 

I finally took the blower out and found that the motor was stuck. It won't spin freely even I use my hand. Could anyone tell me how I can oil it? Thanks!

 

Those bearings look to be permanently sealed which means replace the motor because you can't lubricate it.

I have had good luck entering the part number of a device (turntable motor in an old microwave was one) into the search box on one of the search engines. You will be surprised at the number of hits you get. Some will be online auctions, some will be parts houses, and some will be repair shops. The aforementioned turntable motor was over $80 from the microwave mfr. I found a brand new one, identically marked, from a motor mfr, for $35 by carefully shopping.

Good luck.

 

The inducer and blower motors are pre-lubricated and require no additional lubrication. These motors can be identified by the absence of oil ports on each end of the motor.

That means the motor needs to be replaced. There is no place to put oil in. You could try a couple of drops down next to the shaft but it's usually the back side that needs the oil and it's a sealed area.