Heat Pumps

I have a weather king heat pump and it keeps freezing up outside to a block of ice . I tried replacing the defrost time and that did not work I can’t even manually put it in defrost , so I tried putting a new thermostat on and that still did not solve the problem . It is getting frustrated to have to keep checking the heat pump and putting it in AC mode to thaw the unit down . Does anybody have any other suggestions . Thanx


What was the outside temp when it freezes and what is the output temp at the closes heat register to the unit. output temp should be 110 if it is not it could be low on gas, Other things to look at clean filter and fan .
room temp
out put temp
outside air temp
lets us know these factors

Your indoor thermostat has nothing to do with the defrost cycle. The defrost is generated from one of two places the outdoor stat or the control board within the unit. Are you troubleshooting this unit your self or are you just changing parts until you find the right one. Not trying to be vacuous here but if you have no training on these units it will cost you must less in the end to have someone trained in HVAC to repair your defrost problem

I am certified in HVAC and I was told by someone that was also certified that those 2 may be the problem .

I am geting 115 coming out the register , it has been about 40-45 degress outside, filter is clean, inside Acoil is clean .The heat does work but after a while the ice biulds up so much that the fan starts to hit the ice thats how I know that the ice is biulding back up again.

Stan if indeed you are certified in HVAC you should know that the indoor stat just controls the mode heat or cool and off and on. I don’t know what year your unit is, the older ones had a embedded thermostat in the outside condenser that was factory set to generate a defrost cycle when the outside condenser reached the set point. The new ones generate defrost according to time as set by the dip switches on the control board. A low freon charge will not make the unit not go into defrost if anything a low freon charge can create excessive defrost cycles. If the reversing valve was bad you would not be able to shift the unit manually to cool from the indoor stat. so that eliminates that. The only thing left is the type control device you have installed that generates the defrost cycle.

My 2001 Bryant heat pumps have both, a control board with dip switches for setting the frequency of defrost and a thermostat on the outside coil to control the duration of the defrost cycle.

If they don’t use an outdoor stat to initiate and terminate the defrost cycle, they use a pressure switch (as refrigerant pressure is relative to temperature).

Also some units use air switches that measure the restricted air flow through the coil when is is on it. These are used in conjuction with another temp or pressure sensor.

Stan, can you accelerate the defrost board timer and initiate a defrost?

If not, jump the OD sensor at the board and try it again.

If it still will not initiate, the timer is bad on the board.

Even if you replaced it, the new one can be bad.

If all this will initiate a defrost and it still won’t work on it’s own, you have a wiring problem.

When it goes into defrost cycle does the outside fan run? It sounds like the defrost cycle is to short or it is not coming on at all. i tend to agree with David, Maybe the new control may be faulty. As Bruce said some have dip switches to change times depend on the control have you checked that yet? If your getting 115 it is not low on gas. Coils clean fan fins clean filter clean Only thing left is the defrost control ethier not set for the area your living in(dip switches) or new one is not working BTW if is a pressure switch is the shredder type? it could be that the shredder valve is defected

unless the electric heat is on. 115 is high for a HP if it’s cold out.

He is manually defrosting it with a/c.

I think the issue is with the defrost controls.

Dan, If you have not got it fixed, call me.

Its Christmas, you don’t need this!

Yes i do think your right only thing it can be

On mine, if the defrost timer board puts it into defrost and the sensor mounted on the outside coil is not cold enough or bad, the defrost mode will stop in about 10 seconds.

Sounds like the sensor is stuck in the “not cold enough to defrost mode”.

David I canot accelerate it I tried it it does not go int to defrost it just clicks . I am not to familiar wih jumping the od sensor . I think I might get another board and try it . The heat works it’s just a pain when alot of ice accumaltes it stops the outside fan from running and 115 is with the electric heat on .

Thanx for your help .

It can be tricky.
When you jump the pins to accelerate the clock, if you don’t pull the jumper fast enough it will just click as it flies past the timeout setting (dip switches, or time jumper).

If it is clicking, that means it may be doing something.

In most cases it is the outdoor sensor that goes bad.
There are two wires on the Def board (same size and color) that go to the sensor. Just jump these two at the board and give it a try. It should say something like “Def” “in” “out” at these wires.

David I found the problem there was I thermostat wired thats was not connected on the heat pump the wire nut came off and was not making a conection it is working fan now . Thanx for the help .