98 Model 405 A/C Issue

[AnamCara]

I know its kind of late to chime in but does water flow from the aft ac cooling water overboard discharge when the forward ac is on? You mentioned that it is a single pump system.
Possibly just an issue in the pump relay control for the aft unit?

[Viper]

In a single pump system, when any one of the AC units calls for water, it will flow through all the AC units on board. So if you have 3 AC units and you turn on just one, you'll see 3 overboard discharges if each unit has it's own discharge port.

[g36]

Fwiw. on my add on 3rd unit in my 405 aft cabin it is a totally separate system including its on water pump. I don't know what would have been the setup from carver with 3 units. I know mine was oem with only 2 hvac units so those do share a common relay box.

[Viper]

One pump for three units is the norm. I have seen a second pump used in boats that have an additional air conditioning unit in an enclosed flybridge.

[Midnightsun]

I can confirm the factory setup is a single water circulation pump for all 3 units. Any AC that has a call for cooling or heat, will activate the centralized pump.