I replaced the filter with one provided by the customer. I operated the unit on heating mode. Temperature rise was a little low and discharge pressure was slightly low. I realized the blower speed needed to be decreased to “low.†I checked to make sure the defrost cycle initiated and completed and that the auxiliary heat elements indoors were operating. The unit is operating normal. I recommend adding a hard start kit to the outdoor unit. Customer also has an issue with the drain line at the air handler blocking the filter access. It does make it difficult to replace the filter. To fix it the drain would either have to wrap the other way around the unit or the trap be switched out.