A/C questions

[ChargerCharlie]

What is the true function of the capillary tube system on the water heater valve that goes into the heater box? Is it necessary for the A/C and/or heat system to work properly?

Also; The A/C delay relay on the bottom right hand of heater box. It's purpose is to limit humidity in the car and will cycle the A/C compressor for a minute or two in the heat and defrost mode and then shut off. My system is wired correctly and it comes on in both heat and defrost but stays on. The system is not charged. Will this problem correct itself once the system is charged or is there another issue?

[John_Kunkel]

The capillary tube senses the heater core temperature and automatic heater valve opens/closes to keep the core at the temperature set by the heater control. Many heater valves don't have one and work just fine but the temperature must be monitored and readjusted as needed.

Not sure of the function of the delay relay but most modern cars run the compresor continuously in the defrost mode.