Heat Pumps and Electric Heating - Ruud heat pump trouble

I have a 16 yr old Ruud 4 ton heat pump split system. When I turn on the heat it heats for about 4 minutes then switches to cooling the heat strips come on when the temp in the house begins to fall. After about 13 min the unit cycles back to heat. After about 4 min it goes back to cooling. The vapor line is running around 125 degrees and 250 psi when the heat is actually on. Condensing coil and evap coil have been cleaned and the defrost board has been replaced. Lastly when it switches to cooling the condenser fan continues to run, and and a new electronic t-stat was installed over the summer.

Sounds like you miswired your defrost control or simply bought the wrong one. From what I read you are saying that the unit defrosts after 4 minutes of heat time and it defrosts for 13minutes. I think most older Rudd heat pump units utilize a electronic defrost control and 90% of those control boards would only check for a defrost cycle after every 30 minutes of heat time, and then only if it were set to the lowest pin position T1 I think. Plus your defrost time should only be around 5 minutes. Post your exact model number and I will look on the Rheem site and see what your unit uses. There is a procedure for testing the defrost board.

thanks for the response
Mod UPGC-037JAS
I put the new defrost board in because this is the problem I was already having and unit acts the same with the new board as it did with the old. electronic t-stat was put in over the summer and a/c worked fine didnot realize iI had a problem till heating system. could miss wiring the t-stat cause this trouble

Don't see how a miswired tstat could cause this problem. Usually when they are miswired folks either get no heat, or reverse their heat and cool by not knowing how to energize their reversing valve. The tstat is typically defrost agnostic. Sounds like you have some other issue with the defrost cycle that is in the outdoor unit.

First thought after rereading your first post is to make sure that the unit is actually reversing into cooling mode, you stated that the condensor fan continues to run so is the uniot reversing or is the compressor just cutting off? Do you hear the Whoosh sound when it changes over? Please note that the Rheem/Rudd PGC type units had a option for a demand defrost control and the standard timed defrost boards will not work on those units.