The pump is being replaced because it's not putting out enough pressure and the gas is not circulating. The evaporator pipe is not cold.

The system was evacuated and re-charged just a few days ago, and it made no difference. On the charging machine the high pressure gauge was showing too low, and the low pressure was too high.

If a component with threaded connections is replaced, is any sealer necessary on the threads? If so, what type of sealer?

I was planning to use a Denso pump, which I believe comes pre filled with oil.

Thanks