Blower Cuts Out In Cooling

**flanders** · 05-17-2012, 10:31 PM

Carrier 48TFE012-A-611 ser 1004G50704
This unit will run for about 1 minute normally and then the blower will cut out. The contactor for the blower motor has 27 volts at the coil until it cuts out. Then it shows no low voltage. The compressors and condenser fan motors will continue to run until the unit cuts out on low pressure. The blower will not come back on until you cut power to it from the disconnect and then reestablish power. It looks like to me, the only thing that could cause this condition is a bad board. I haven't seen this before and was hoping that one of you have. If you need all of the gauge readings and etc, I have them but I didn't post them since I don't think they are relevant to the problem. Thanks in advance!

**pvc1984** · 05-17-2012, 11:04 PM

Are you losing voltage at G when the blower cuts out?

The only advice I could give without being there is just look at the wiring diagram and trace back what's providing 24 volts to the coil.

**pvc1984** · 05-17-2012, 11:09 PM

Nevermind that question...Forgot you need 24 volts to G on a carrier for the compressor to start.

**Six** · 05-17-2012, 11:09 PM

Originally Posted by flanders

Carrier 48TFE012-A-611 ser 1004G50704
This unit will run for about 1 minute normally and then the blower will cut out. The contactor for the blower motor has 27 volts at the coil until it cuts out. Then it shows no low voltage. The compressors and condenser fan motors will continue to run until the unit cuts out on low pressure. The blower will not come back on until you cut power to it from the disconnect and then reestablish power. It looks like to me, the only thing that could cause this condition is a bad board. I haven't seen this before and was hoping that one of you have. If you need all of the gauge readings and etc, I have them but I didn't post them since I don't think they are relevant to the problem. Thanks in advance!

Does that unit have the fan contactor/ timer assembly. It just a fan relay with a small board
attached to it.

If it does or it gets it out put from a board jump the fsn coil wire to R to keep it running and then monitor the out put at the board.

Not much to those Carrier RTUs.

**Dallas Duster** · 05-17-2012, 11:28 PM

Go to the economiser board if it has the 4 LED`s on it and bypass the G terminal so the board doesn`t control the fan. Then look for corrosion on it. Change as neccessary.

**VTP99** · 05-18-2012, 12:08 AM

Check the fan logic for power in and out also the blower relay. Check t-stat as well.

**flanders** · 05-18-2012, 09:39 AM

Thanks for the replies. I'm going back today so I'll let you know if your suggestions worked.

**beenthere** · 05-20-2012, 07:53 AM

What did you find.

**flanders** · 05-20-2012, 05:23 PM

Sorry that it took me so long to reply. When I arrived back on the scene the unit had new problems. Blower still was not running but now the reset button on the economizer was tripped. I reset it and the unit cycled off on high pressure. I found that 1 of the 2 condenser motors is bad. I replaced the motor and dual capacitor (10/10 mfd) on Friday. With the economizer reset and the new condenser motor, it seemed to operate fine. I waited for about 30 minutes and then I split. I am going back this afternoon to check on it again (and drop the bill off). Even if everything is fine, I am still concerned with the economizer reset being tripped. I will keep you posted.
P.S. Something else that I found was that someone jumped out the board where the 5V fuse is supposed to be so there must have been a low voltage problem before me.

**VTP99** · 05-20-2012, 05:34 PM

Originally Posted by flanders

P.S. Something else that I found was that someone jumped out the board where the 5V fuse is supposed to be so there must have been a low voltage problem before me.

Or they did not have a replacement fuse. Are you planning on replacing it ?