[uncletink]

Ok new coleman 5 ton heat pump with defrost problems, has the new demand defrost board where the ambient sensor and the coil sensor work together to figure out if the machine needs to defrost, board number 1157-83-9021a , i already changed the board and i always change the defrost sensor but i did not change the ambient sensor , so as right of now no defrost i understand that the pin sitting is suppose to be on 1 but what does the letter p do

 

[beenthere]

P is programmed. Thats what is used when the board is installed at the factory. it means it was programmed specifically for that unit.

So are you saying it neers goes into defrost. not even its 6 hour compressor run time defrost? Or that the coil seems to frost up a lot, and you don't see it defrost.

 

[hvactech126]

will the unit defrost if you short the test pins?

It does not matter what the other pins do where the jumper is. York/coleman says that it should be on 1 so that is what it needs to be on.

 

[uncletink]

no defrost cycle at all put the board on over 12 hrs ago, even through the test pin nothing, the curve is set at 1 just like york said , im just wondering if i change the ambient sensor if it would work

 

[beenthere]

Might. The board needs to see X degree difference between ambient and liquid line temp, or it won't go into defrost. Except for its 6 hour of compressor run time. Which it won't do, it the ambient sensor indicates its above X degrees outside.