Performed diagnostic on 4 year old Lennox system. Not heating. Cycled system for heat. Outdoor unit is unresponsive. Circuit board was showing error node for low pressure. Checked and found refrigerant level to be low. With approval charged system up with refrigerant. Cycled system with proper charge, low pressure switch is still not closing. Pressure switch is bad, need to order and return to replace. Will also be adding Leak Dye and Seal. Will be ordering part on Monday and will advise with eta on part. System is not operational. Collected $100 Today, $848 will be due upon completion of work.