Heater- Raw Water or Coolant?

[unclejessie]

Does anyone know if the heaters on a 2015 G21 are run off the hot lake water (after the heat exchanger), or the hot coolant. I have the 409 engine and I think the answer is the hot coolant, but I want to be sure. Thanks.

Uj

[vision]

The heater has coolant not raw water.

[Quinner]

It would be dependent on whether your motor is open or closed cooling, heater ideally would be plumbed directly to motor cooling regardless. Excalibur 343 is the only motor that is available with raw water cooling, so if you have a 409 or higher HP then your motor would be closed loop. Short answer, your 409 is closed cooling and your heater is part of the closed loop with af/coolant.