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Hi All. Any help is appreciated with my thermostat. An E2 code appears when in cool mode for my heat pump but works OK in heat mode.(heat pump will kick in and heat.) The thermostat just clicks and flashes E2. :(
I believe it is a Carrier programmable tstatccpdf01-a thermostat that controls a Carrier dual fuel model 58mxa Weathermaker 9200 and a 38byb split system heat pump. Unit was installed around 2000. Serviceman worked on the heating side of the heat pump this winter. A fuse was blown on the circuit board inside the house and he said a wire was loose on the outside unit.
If I select auto mode the same E2 code appears.
Transformer appears to have about 24+ volts at R and C wires at the thermostat. Actually 27.5 volts.
 

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AKA HVACTECHFW
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if you have a owners manual it should explain E2 in the manual. This is what I found.....Brownout condition or too low of voltage to thermostat. Double check wiring and check for 24 vac between R and C. E2 will clear 15 sec after proper voltage is restored.

check you manual or post model number stat.
 

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AKA HVACTECHFW
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it could be the reversing valve is bad and has a lot of resistance when power is applied causing the overall voltage to drop and cause the code. Yes that is possible. It could be many things such as the reversing valve sticking and causing a pressure switch to open.

Here is a link to your homeowners guide...OMTSTAT 3
 

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tech126 is probably more familiar with your stat then I am. But I would check for loose or corroded wire connections at it and at the air handler and outdoor unit.

tehn if none were found, ohm out the contactor coil and RV coil(turn off line voltage first).
 
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AKA HVACTECHFW
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Eagle, do as beenthere suggested and check all the wiring connections in stat, furnace, and HP first. Then check the resistance of the contactor and RV coil.

Also, add more info in a new post instead of updating your old post. It is hard to tell there is new info present unless watching closely.
 

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Best to keep it all in one thread.
 
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