Changed batteries and now cannot get an outdoor reading.how do I fix this?

Have you changed the batteries in the outdoor temperature sensor?

Try cleaning the outdoor thermometer transmitter unit by opening it up enough to spray compressed air (Ultra Duster or similar) on the temperature sensor. It fixed the hh.h error for me.

My pp-sirmt1 outdoor remote sensor display is blank and the clock displays "- -" for outdoor. I have changed both the remote and clock potteries even though they read "Good" on a battery tester. Can I purchase a replacement outdoor sensor unit?

It might not be in range I wouls try bringing them closer together or bring your outdoor sensors inside untill yoh get a reading

Have you changed the batteries on the outside sender unit?

I changed the batteries on mine and it reset itself. That was easy.