Fan only staying on for a few seconds and then shutting off- AC not cooling

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zannej

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I have a Trane whole house AC system. The outside unit was replaced I believe last year. The inside unit was installed circa 2010. I had a previous issue with the outside unit where a wire in a molex connector was loose and that was fixed by the installers for the outside unit. The installer for the inside unit ghosted me. The local guy who worked on the older outside unit before passed away a few months ago. I don't trust the competency level of the last local who checked on things.

We've been having thunderstorms so I haven't gone outside to see if the outside unit is kicking on or not. The thermostat is relatively new-- its a Honeywell one that I can connect to over the LAN. Info on what system I have in this thread: https://www.houserepairtalk.com/thr...-turned-to-heat-mode-for-a-couple-days.32182/

I recently changed the filters but I checked and they are still 90% clean (no buildup at all in the top 90% of the hallway filter-- only a little bit of lint at the very bottom). Poured bleach down the condensate line. Switched from automatic mode to off to cold. It tried to cool but the fan kept doing that thing. Set the fan to automatic. I did note that at one point the thermostat said "waiting on equipment". I turned it to Off mode and turned off the breaker for an hour and then turned it back on. It then tried to cool again but the fan will come on for maybe 3 to 7 seconds and then shut off. About 10 to 30 seconds later it tries again. I turned AC mode off but tried to have the fan run on Circulate or On but it still did the same thing.

I've read that the symptoms can be caused by low coolant, electrical fault, clogged filters, or capacitor failure. I've ruled out the filter I think. We have had a lot of power surges lately so I wonder if it caused electrical damage or if the fan motor is going out.

Any other tips on how to troubleshoot and what I can do?
 
Indoor fan coming on, then off early, then back on, etc.:
Try This Easy Test-
Set it to call for cooling. When the indoor fan turns itself off early, look at the outdoor unit. Is that fan running? Is the compressor running? If that's the case, almost 100% certainly you have a bad Run Capacitor at the indoor fan. This is very common.
Paul
 
Thanks, Paul. I did that test before I read your message. First time, compressor didn't come on and the thermostat said "waiting for equipment". I turned the breakers off and on again (there are 2 breakers for the AC) and the outside unit came on and fan was running. I could hear it cooling from the inside unit as well. Obviously air or something was passing in to the system. But after awhile it turned off but I was busy taking trash out and didn't check the compressor. I'll try that test again tomorrow during daylight to see if the compressor stays on or if it shuts off. I do know that it stayed on while the fan was off.

I'll have to locate the run capacitor for the indoor fan. I know what the capacitors in the outside unit look like, but I've never opened the inside unit up.
 
When you do the test, remember that there most likely is a time delay (or 2 or 3 ...) to stop the compressor from starting against high head pressure. Give that (or them) time to count down & start the compressor.

Example- My Home: Thermostat has a 4 minute minimum delay, indoor unit has a fixed 3 minute delay, outdoor unit has a fixed 4 minute delay between cooling calls.


The run capacitor is most likely strapped to the motor mount. It is oval shaped & probably says "7.5 mfd" or 7.5 µf. (The number before the mfd or µf may not be 7.5)

Paul
 
Would the capacitor be in the outside unit or inside unit (aka AHU)?

Someone on an HVAC forum sent me the following info:
Lets go over the low voltage wiring -
R (Red) is 24 VAC to stat
W(O/B) (White) - heat, puts the reversing valve into heating mode (most cases de-energized) - R switches power to W for heat
W2 (Brown) is aux or auxiliary heat - normally turns on electric heating elements on heat pumps or 2nd stage of heat on a gas furnace
Y (Yellow) - R connects to Y to turn on the AC
C - Common to the R terminal

With the above, we test at the AHU that we have a constant 24 VAC from R to W or (O/B) - On a call for heat
With the above, we test at the AHU that we have a constant 24 VAC from R to Y - call for AC

Not sure where that would be checked. Either inside the AHU or the thermostat. Waiting for a reply.

I do know that you're supposed to discharge the capacitor on the outside unit or you can get a nasty jolt.
 
Be aware, Zannej, that the colors in your chart above are someone's version of "standard" color coding.
In real life, the colors may be quite different. Look at the terminal designations on the board to which they are attached.

If the outdoor unit is coming on and the indoor fan stops as you originally posted, none of the tests in the chart you attached are needed or relevant.

Paul
 
Would the capacitor be in the outside unit or inside unit (aka AHU)?

I do know that you're supposed to discharge the capacitor on the outside unit or you can get a nasty jolt.
You asked where the capacitor is & mentioned shorting it out:

Capacitor for indoor fan is usually attached to, or near, the indoor fan motor. It will be an oval shape, about 4 - 6" long. Usually they are grey. (Hint: Look on line for the replacement for your model. It'll have a photo of what you're looking for.)

Discharge Note!
Instead of discharging the capacitor at all, the safest is to remove power from the unit for a couple of days before handling.
If you discharge

If you discharge it, it is much safer to use a resistor clipped across the terminals with insulated alligator clips. Calculators are available to tell you what Ohm value you need once you find your capacitor's rating (printed on it). Power Off & Wear safety glasses.

If you are going to very dangerously cheat and put screwdriver across it, wear safety goggles. (Not glasses- goggles) and heavy gloves to catch shrapnel.
Paul
 
Thanks, PJB12. My AHU looks to be model 4TEC3F60B1000AA
I'm looking through photos and parts stuff. Found this site for parts https://www.repairclinic.com/ProductDetail/1149336
First, make sure your motor uses a run capacitor. Some don't, such as ECM motors.

Next, make sure the run capacitor is bad.

Once you know yours is bad, read the numbers on it to find a generic equivalent.

Test yours or risk it & buy a new one to try. They're cheap.
I ordered three 440/370 volt 7.5 mfd run capacitors on line just yesterday for $3.06 each.

Be sure to check the ads on this forum to see if one of the sponsors sells what you need. Hopefully your purchase will help support the forum.


Paul
 
My friend said that it does NOT use a run capacitor. Found the manual for it but brain is not cooperating with me.
https://www.manualslib.com/manual/2749461/Trane-18-Ge08d1-10.html

Trying to keep an eye on Mom's blood sugar levels and get things sorted with her taxes. I have the AC turned on now and checked that the outside unit does stay on and it has cooled a little bit, but the inside fan is just not staying on.
 
The wiring diagram isn't in the manual that you linked.
Try turning off the power supply and removing the front cover. The diagram will be pasted inside that or one of the other covers. On it, you can find if there is a run capacitor for the fan motor.

Or, look around near the motor for a capacitor.

It sound like you're every busy. Perhaps calling a heating person would take some weight off your shoulders.
 
I'm pretty sure the diagram is on the inside panel. I think I saw it when they were working on it. But I don't know how to take the panel off. I saw a video where the blower motor was replaced bc of the same symptoms but it was a different Trane unit. It looks like my unit may use a continuous torque ECM blower motor MOT13120. As a note, the video started with the panel already off, but the AHU was on the roof and was a different shape than the one I have.

My friend said he's going to try to come out tomorrow after work to see if he can take the panel off and look at it.

I have been calling the original installer and getting an answering machine. Left several messages but still have not been called back. I'm going to call again after lunch.

The person I had look at the outside unit gave me bad vibes-- don't trust him. And the people who installed the outside unit are over an hour away. The only person locally that I would have trusted, aside from the original installer, is the one who allegedly killed himself.
 
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Typically, to remove the panel: Turn off the electricity, grab the panel near the air opening slot, lift.

Since you're having trouble getting a repair person, perhaps your local gas or electric utility company has a service program or makes repair calls. They tend to be honest because they have nothing to gain by selling you new equipment.

Paul
PS: If your motor is ECM, there will not be a Run Capacitor.
 
No local gas and the electric company sucks. However, they came out, they took off the top panel and flipped some breakers. There was no run capacitor, as you said.

Here's the diagram that was on the inside cover thingy 1711562740837.png
They took out this big honking thing:
1711562781433.png

They said the "brain" and "squirrel cage" were bad and had to be replaced along with the motor. They had a used motor on hand that still worked. So they replaced those parts and put it in that big outer casing thing and put it back in.
1711562868874.png
when they put the outside cover back over it started making almost a whistling sound. Can really hear the air moving. It also makes sort of a low hum. It's way louder than the older one, but it works so I'm fine with that. Used to only hear a whooshing air sound when the fans came on, now hear the low hum,. But it doesn't bother me.

It was $600 flat for parts and labor.
 
I'm glad it's working now.

The "big honking thing" you mentioined is the blower & motor assembly.

If you are not certain that the new sounds are benign, it would be good to call the service people back right away. This way, it is easier to convince them that the new sound is part of the repair.

Try to get good photos of the wiring diagram and paste them into one file. The papers disintegrate over time. You'll now have a copy on your computer & backup place.
 
Ah, the motor assembly. I wasn't sure what part was what. I know they mentioned "squirrel cage" but I wasn't sure what part that is. I need to learn more about it.
The sound was being made while the repair people were here. I commented on it but they didn't seem to think anything of it. I think maybe its because its a different fan. I'll have to try to record the sound with my phone. The fan was making less noise before the compartment was closed back up so I'm guessing its air whistling somewhere or something. Sort of like when my nose whistles. I'll have to see if the electric bill changes at all now.

I have folders on my computer where I save the photos of the hvac system, model numbers, diagrams, pdf files etc.

Right now I need to focus on getting the house cleaned up and making sure Mom gets the taxes done. She's procrastinating on it.
 
If they put in a used one (a salvaged one, which I think is what you posted earlier), then it might be a little noisy, like the bearings are a bit worn. If this is a temporary fix you may decide to live with it. But if this part is as good as it's going to get, then you may want to address it.
 
Yeah, not sure what I can do to address it. I can deal with the noise as my other fans are pretty loud too.
 
I replaced the blower motor in our old furnace in our old house. They called it an air handler because it was a gas furnace and an Air Conditioner. Within a year or two, the heat exchanger tubes corroded through and the flame was escaping, tripping the flame sensor protection devices and shutting the furnace down. That resulted in a new system. The original Goodman system lasted about 25 years.

Here in our area in Alabama, it is common to have the whole system in one big box outside the house. There's just a duct coming into the house. These units are cheaper than the split systems that have the air handler/heater/evaporator in the house and the condenser outside, but I'm told the all in one units don't last as long.
 
I replaced the blower motor in our old furnace in our old house. They called it an air handler because it was a gas furnace and an Air Conditioner. Within a year or two, the heat exchanger tubes corroded through and the flame was escaping, tripping the flame sensor protection devices and shutting the furnace down. That resulted in a new system. The original Goodman system lasted about 25 years.

Here in our area in Alabama, it is common to have the whole system in one big box outside the house. There's just a duct coming into the house. These units are cheaper than the split systems that have the air handler/heater/evaporator in the house and the condenser outside, but I'm told the all in one units don't last as long.
Believe it or not, horizontal flow outdoor combination units are not unseen way up here in Michigan. Not common, but not unseen. They're most often found at houses with crawl spaces instead of basements. I've seen commercial rooftop units serving homes. In smaller commercial (like restaurants, strip malls, etc.) these are the most common type of heating-cooling & are installed on roof curbs.

I sometimes help a friend with his very old Goodman outdoor horizontal & am surprised when it is zero degrees-F outside how much temperature drop there is in the short distance of duct to the crawl space and to the first register!

Paul

PS: I'm not surprised that your Goodman lasted 23 years! My brother lives at the tip of Michigan's Upper Peninsula and has a few year old Goodman that only failed once- when the lake snow drifts piled up 16 feet & covered the combustion air intake. I've worked on some ancient Goodmans. Goodman's have always been brutes.

The only Goodman complaint I ever had was that the above mentioned horizontal flow uses Honeywell's "Smart" gas valve. Those are unreliable and scary expensive! Other than that one model, all the others I've seen use inexpensive, generic parts.
 

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