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JLeather 11-04-2012 07:06 AM

I need some help troubleshooting, my heat pump stopped working last night
Last night at about midnight my wife noticed the thermostat was flashing something. I took a look at it and it said "E2" in between displays of the temperature. The thermostat is a Bryant TSTATBBNHP01-C. According to the manual that is a "Low Voltage Fault". I was too tired to dig into it at that point so I took the easy way out. I replaced the filter and cycled all the breakers and went to bed hoping that it was a fluke. This morning the house is COLD (no surprise). So I got out the manuals and dug a little deeper.

The thermostat is no longer flashing the E2 code. It just says that the heat is On, and set to 71 (although the house is currently 63 and falling). It also says the e-heat is on (quite possible because it's 35 out this morning). I also toggled the manual Fan function and the fan did not come on.

The air handler is a FV4BNF002 and I think the outside unit is a 650A but I need to double check (if it matters). I took the thermostat off the wall and got out my multimeter and I have no voltage between R and C (I read on another site to check that). I also checked at the air handler and got no voltage between R and C. If I understand that correctly that means that for some reason my air handler has shut down, most likely a fault of some sort. I'm not sure what to check next. I don't think this unit has an LED for trouble codes (haven't seen one anyway). What are the most likely causes of no voltage at R and what do I look for?

Thanks in advance for any help you can give me.

JJboy 11-04-2012 07:56 AM

You have to close the door safety switch to power the air handler. Just FYI check the power voltage (black and white wires) at the transformer also check for 24vac voltage ( red and blue wires). You should see the LED on the control board flashing or on.

hvactech126 11-04-2012 09:18 AM

there is no door switch on an air handler............ There is likely not a control board with a flashing diagnostic led either............

JLeather 11-04-2012 12:32 PM

Yeah, no door switch, just a cover that you have to remove 4 screws to get through. Also no control board, all basic stuff it seems. I located the low-voltage circuit fuse and it was blown (5A). I replaced that and everything is working normally for a few hours now. In my past experience, however, fuses don't just blow for no reason. Is it a sign that my transformer is in trouble or could it just be a fluke?

hvactech126 11-04-2012 05:57 PM

it is a sign that you have an intermittent short, good luck trying to find it. Look for chewed on wires at the outdoor unit.

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