No high speed on new A/C blower, used to work


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Old 08-08-10, 10:33 AM
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No high speed on new A/C blower, used to work

Ever since the neighborhood lost power for about 15 hours, the blower won't run on high when set to cooling. I powered off the unit, switched it to med-high speed, but doesn't change the blower speed (i.e. exact same air volume). This is a brand new Gibson unit, maybe 2 months old, worked perfectly until 5 days ago. Air is still cold, just no high volume. Thoughts on how to fix?
 
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Old 08-08-10, 03:27 PM
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Voltage spikes from the power outage probably fried the control board for the fan. Since it's two months old and still under warranty call your dealer.
 
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Old 08-08-10, 05:21 PM
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Not clear here.. When you changed the speed to next level down, the blower did or did not run?

FYI, lot of time High speed is too fast for most A/C. Ideal settings is 400 cfm per ton. For an example on my system, my A/C blower speed is lower than my heating. (low)
 
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Old 08-08-10, 08:14 PM
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Sorry that I wasn't clear. Before the power outage, the furnace worked fine.. then when it got hot, the A/C worked fine.

Since the power outage, the A/C blower volume has been way less then normal. I switched the cool blower speed switch on the circuit board from high to med-high (just for something to try) but the blower continued to run, at the exact same diminished volume. It used to run high, now it runs way less, no matter what the switch says.

So I just let it run at it's crippled pace, but coming home today, the blower has just stopped working altogether (but the compressor outside was still running). I turned the cool/heat/off switch to off, and then the fan from auto to "on" (which normally would turn on the fan) and I hear the click on the thermostat to turn on the fan, but the fan is now permanently off.
 
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Old 08-08-10, 08:18 PM
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Sounds like lighting/power surge hit something on the furnace.

Leave it off, and call for service in the morning.
 
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Old 08-09-10, 09:25 PM
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Installer was out today, said the blower/motor was bad, and he'll replace it tomorrow. Hope it's not the circuit board too... flipping 90 degrees in the house now.
 
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Old 08-09-10, 09:49 PM
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I know it's not fun being in a hot house.. Been there once myself! We end up going to my aunt and uncle that night.
 
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Old 08-09-10, 10:08 PM
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sounds like a ECM motor control board issue, but it is under warranty so for sure get a BRAND NEW COMPLETE MOTOR.
 
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Old 08-10-10, 05:23 AM
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Thanks for the comments. I have my fingers crossed!
 
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Old 08-10-10, 01:22 PM
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A/C guy finished replacing whatever, house has cooled 2 degrees in 45 minutes. Thank god! unish:
 
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Old 08-11-10, 04:02 PM
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I've been poking around my air handler unit learning about how it works recently, and from speed control board to blower motor are 14 white wires, a blue wire and an orange wire. Does anyone know how you could bypass the speed control to make the motor run, or how I could find that out? Could it just be putting 24v to the blue and orange wires? I can't for the life of me imagine what all the other white wires do. If my circuit board ever fries, and I can make the motor run just by putting 24v to 2 wires, I would rather do that than go without cooling for a night like this guy did.
I have 4 years left on my warranty but will need to know how to take care of things myself after that. I've found the speed control board online Trane CNT 03600 ignition control board* but at $40 it is not really worth having a spare. If mine goes out I'd like to know how to bypass it until I can get another.
 
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Old 08-11-10, 09:59 PM
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be very wary of bypassing any wiring on these new units, the term unintended consequences comes to mind.
 
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Old 08-15-10, 08:15 AM
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Please don't hijack threads!

So my A/C is barely working again. After the "fix" of replacing the motor, it worked for 4 days. Now I'm getting about 80% of the air volume, but it's only cool air, not cold like before, even after the fix. And it's not maintaining temp, even after running all night, it only dropped to the outside temp (80 down to 76). I noticed a baseball sized block of ice on the copper tube connection to the condenser unit outside, and a smaller one at the same copper connection inside... what the heck is going on???
 
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Old 08-15-10, 08:43 AM
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IF you got ice on the line, and the air flow is less, the coil inside is freezing on you.

Call for service, and shut off the unit.
 
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Old 08-15-10, 08:53 AM
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Thanks for the reply! Why would this be happening on a brand new unit? Do they need to be "tuned" or something? It was installed in April, and it worked great through the hot summer until a few weeks ago with the power failure.
 
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Old 08-15-10, 07:21 PM
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It can be a numbers of things.

-Low charge.
-Air filter dirty/plugged.
-TXV issue.
- list can go on, so best to call them since this was just put in. Unless you haven't change the filter.
 
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Old 08-16-10, 05:34 AM
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I changed the filter right before he fixed the motor, then the flow problem started 4 days later.

So yesterday I turned off the cooling, but left the fan on for about 4 hours. Must have melted any ice on the coil because I turned the A/C back on and have full flow and full cooling. It cooled the house sufficiently in about 6 hours, so I left it on over night. Now this morning, I see more ice on the line outside and the air flow seems about 80 or 90%. Something seems to be causing it to ice up over night??
 
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Old 08-16-10, 06:32 AM
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What was the outdoors temp in the over night hours?

Again, it can be a numbers of things. don't let this go any more before you get water damage on the new furnace.
 
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Old 08-16-10, 10:21 AM
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Low of ~63, 65-75% humidity last night. I called the service guy, he's coming back out today... He made some comment about maybe I'll not be able to keep it so low over night.. but I figure 72 isn't asking too much from this A/C, especially since it's been working great, even through the hottest overnights... Am I wrong?
 
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Old 08-16-10, 02:09 PM
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If your coil has TXV, 72˚ shouldn't be an issue, I don't suggest setting A/C any cooler than 70˚.
 
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Old 08-16-10, 02:47 PM
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How do I know if the coil has TXV? The unit model is KG7SA 072C-24B.

Service guy called, said he thought there was a loose fitting on the small line (hot side?) and tightened the fittings. He said it definitely needed a charge, so I guess it was leaking? He said things seemed fine when he left, so I'll see when I get home!

Thanks for the replies!
 
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Old 08-16-10, 03:32 PM
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The model # you gave was for the furnace. have one for the coil itself?
 
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Old 08-17-10, 05:49 PM
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Well, it's been 30 hours since the service guy was out, and it has been running great since... and NOT constantly, as it was before. Runs maybe 10 minutes every 30 to 60 minutes, then shuts off. So that's great news I think!

It says:

model: C6BA-X30C-B
pressure: 550 PSIG
oriface size: TXV

on the plenum/coil housing, so I guess that's good??

edit: oh yeah, I remember him telling me it is a 2.5 ton A/C
 
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Old 08-17-10, 06:37 PM
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Sounds like he got ti going and running as it should.
 
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Old 08-17-10, 08:34 PM
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Still wondering why it ran for 4 months perfectly, but then with a power outage had all these problems. I guess it's possible that the outage fried the blower motor, and the replacing of the blower motor caused the fittings to loosen, which cause the coolant leak, which caused the coil to ice up 4 days later?

I hope this is the last of the service for a while

:Homer:
 
 

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