I have an old A/C system and have replaced the old outside compressor with a Bryant reverse cycle heat pump (free and used). Apparently the compressor runs by default in the heat mode. I want to make it run only in the A/C mode. Can Anyone tell me how to do this. I am using the old thermonostate. Only 2 wires.

You will need to apply 24 volts to the reversing valve coil so it will activate and be in the cool mode.

I must ask, was it installed right,is it a package unit or a split system ,with the a/c-HP out side and the air handler on the inside? YOU SAID OLD OUTSIDE Compressor,making me think it's a split system if so was it vaccumed out and charged correctly ?

I agree with hvac1000. You need 24v on the " O " circuit at the heat pump to make it work. A quick fix is to jumper "Y" and "O" at the out side unit if your only using two wires.

I third that, it can be done very easily.

What do you use for 24 volts to get it back in cool mode

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Originally Posted by stevenbyrns69

what do you use for 24 volts to get it back in cool mode

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Step down transformer 120VAC>24VAC. Get them at any electrical supply, HD or Lowe's etc. Use thermostat wire for the 24VAC. If you are lucky, there is an extra pair in the main tstat line.