reversing valve power

[chrashley]

where does the call for the reversing valve come from during defrost? I have a lennox HP that is putting out 4~5 volts during a call for HEAT. It wont go into defrost when forced from the defrost pins (defrost stat jumpered closed) but will defrost if i jumper R-O on the defrost board and pull the fan lead. This tells me the board is bad but wondering why I'm getting the voltage on the reversing valve wire. Any thoughts?

[just_opinion]

where does the call for the reversing valve come from during defrost? I have a lennox HP that is putting out 4~5 volts during a call for HEAT. It wont go into defrost when forced from the defrost pins (defrost stat jumpered closed) but will defrost if i jumper R-O on the defrost board and pull the fan lead. This tells me the board is bad but wondering why I'm getting the voltage on the reversing valve wire. Any thoughts?

It would help a lot if you give us AT LEAST model of the unit. We don't care the color of the unit or the pad it sits on.
Just model baby.

[Trehak01]

On some Lennox residential heat pumps there is a out door temp sensor or coil sensor (I cant remember which and I don't have a wire diagram handy) but you have to jump it out on the defrost board then jump the test pins. I have also seen that there are a few different types of defrost boards that lennox uses, they all work the same but the design of them are different. hope this was somewhat helpful. model and Serial numbers would help a great deal.

[chrashley]

m-12hpb24-9p
s-5803g91461

thanks for the replies so far

[SBKold]

All the boards ive messed with had one PCB relay that energized w2 and o.

24v usually comes from red wire.

[jdblack]

All the boards ive messed with had one PCB relay that energized w2 and o.

24v usually comes from red wire.

X2

If the RV is energized in heating then 24v comes from stat

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[jdblack]

where does the call for the reversing valve come from during defrost? I have a lennox HP that is putting out 4~5 volts during a call for HEAT. It wont go into defrost when forced from the defrost pins (defrost stat jumpered closed) but will defrost if i jumper R-O on the defrost board and pull the fan lead. This tells me the board is bad but wondering why I'm getting the voltage on the reversing valve wire. Any thoughts?

If you jump r to o and pull the fan lead that's not defrost mode that's AC mode without a condensor fan. 4-5 volts may be a bleed through. Is that with the coil hooked up?

Some units have an ambient sensor that wont allow defrost above a certain temp.

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[chrashley]

X2

If the RV is energized in heating then 24v comes from stat

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this is what i thought. i think i just got thrown a little because of the little bit of voltage on the O wire while in heat. Prolly two separate issues. I'll change the board, ad then address the voltage issue.

[chrashley]

If you jump r to o and pull the fan lead that's not defrost mode that's AC mode without a condensor fan. 4-5 volts may be a bleed through. Is that with the coil hooked up?

Some units have an ambient sensor that wont allow defrost above a certain temp.

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Yes, I understand that. I was just trying to say that its not a refrigerant issue. sorry to confuse. Its cold here in Indy, cold enough to need defrost for sure.

[just_opinion]

where does the call for the reversing valve come from during defrost? I have a lennox HP that is putting out 4~5 volts during a call for HEAT. It wont go into defrost when forced from the defrost pins (defrost stat jumpered closed) but will defrost if i jumper R-O on the defrost board and pull the fan lead. This tells me the board is bad but wondering why I'm getting the voltage on the reversing valve wire. Any thoughts?

Now we got model.
This unit has a non-intelligent demand defrost board, which means: defrost stat and time.

Check your 24 volt Common and 24 volts hot AT THE BOARD. It needs it to function.
If you have them AT THE board and did what you did, then replace the board.