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beaumoi 07-31-2011 02:08 PM

Carrier Blower Will Not Turn On
4 Attachment(s)
Carrier model 58CTa070-12 furnace/ac unit built in 03' blower motor will not turn on. On the tstat if I switch fan mode to ON while in cool mode or heat mode nothing happens. If I go to heat the flame turns on but no blower, if I go to a/c the outside compressor and fan turn on, but no blower. Funny thing is that both the heater and the compressor seemed to run w/o knowing the blower wasn't on. The compressor ran for like 4 minutes at least and was starting to create a puddle and noticeable condensation on the side of the furnace.

So to tried to test the fan by jumping the 24v red wire to G on the tstat terminals, nothing, went downstairs jumped the 24V to G on the terminals, nothing (I made sure the dummy switch was depressed so the furnace was on). From the furnace panel instructions for a test mode I jumped the 24v to the test/twin and the test mode started and no blower motor ever came on, the compressor and furnace however did at one point. When the fan should come on I used a voltage tester to probe the wires for electricity going to the fan motor and it didn't show anything was going to it (the tester didn't go beep beep beep..), nothing was on the capacitor with the brown wires going to and from it either.

So it sounds like the motor is probably good since no juice is going to it, and maybe the capacitor (seems like the wires come from the blwr motor for it though) or some relay on the PC board is bad. Smacking the relay for the BLWR didn't seem to do any good. I've read similar threads in the forum and they were close to my issue, but did not have the exact same issue. Any help or troubleshooting steps would be appreciated. Attached are some images, hopefully big enough to make out. The schematic doesn't appear to come out too great, the manual is at and the page is 45. Will try to get it in a easier format to access.


kok328 08-01-2011 12:51 PM

Good job so far but, I have to ask if your getting low voltage to the red wire.
I suspect as you have, that the relay for the fan circuit is stuck open.
I've seen these replace on the control board and I've seen the whole board replaced too.
See if you can make out which legs are hot on the back side of the board for the fan relay and maybe try jumpering the hot to the respective leg to get the fan to come on to verify the problem.
Short of that, you might see if you can replace the fan circuit relay or replace the entire control board.
Any warranty on this unit?

Dennis1 08-02-2011 10:45 AM

Quick easy motor test
You have a white wire comming off of the board ( from the Neutral terminal ) and going to the motor and a black wire comming off the board ( from the cool terminal ) and going to the motor. There is also a red wire going to the heat terminal on the board Unplug these wires from the board and put 115V across the White and Black from an extension cord. Make sure that the red wire is not touching the cabinet of the unit ( tape it up with some electrical tape) If the motor runs its good.

You don't have to worry about the door switch being depressed or any thermostat settings since you will be putting 115V directly to the motor just to see if it runs.

If it does not run it could be the capacitor.
The capacitor can be checked with a digital meter that has a capacitor setting (uf or mfd). First , with the electricity disconnected from the motor, short the two terminals to ground or together with a screwdriver to discharge the capacitor. Then remove the two brown wires and hold the probes of the meter on each terminal of the capacitor. If the capacitor is a 5mf ( the rating will be written on the side of the capacitor) your meter should read 5. Just set the meter to the uf setting

beaumoi 08-02-2011 05:01 PM

Hey guys, thanks for the replies. For some reason I didn't get notified via e-mail once they came through as requested when I posted it via the options so I just saw them. I'll see what I can figure out and post back tomorrow. Thanks a ton!

beaumoi 08-02-2011 06:20 PM

Circuit Board
3 Attachment(s)
Yeah, thinking the circuit board is definitely shot. The green square in the snapshot shows a diode that was actually missing a leg from corrosion, apparently those block flow of electricity from going the wrong direction and I'm betting I need that. The leg was actually not there at all when I opened the case.

The 2nd image shows a bit of corrosion on some I think jumpers.

The 3rd image shows the blower motor relay which looks to be leaking something although I didn't think relays had any liquid in them. Perhaps it came out during my numerous smacking attempts.

From Carrier it sounds like the warranty is good for 10 years if it was registered in 90 days from install, no idea if it was as I moved in a year or so after it was installed. Otherwise I'm SOL and have to pay about.. 330.00. Holy crap, that's a pisser.

beaumoi 08-02-2011 06:26 PM

Anyone know if that damage is normally covered under a warranty? Basement has never flooded to my knowledge and isn't too humid as the dehumidifier takes care of most of that. Seems like they would have sealed the circuit board like they do to some other ones I've seen.

Reading further into the warranty information I doubt the original owner registered it before 90 days and I'm more then sure it was the least of worries when I got the house so I doubt it was transferred..

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