Coolant thermos retrofit - humour me

High molgrips, maybe I missed it, but I'm not clear if you have the Gen I or II Prius.

 

I would love to retrofit too but after looking into it I gave up and bought a hot frog

original hot frog universal Motorvorheizer pre heater

 

Does it actually work? Don't the valves in the coolant system stop it? It appears to be the same as many "circulation coolant heaters" we have here in North America.

 

The software is indeed different. I have a EU spec ECM and when plugged into my car it does not activate the thermos pump upon startup.

At least on my car there are actually 3 PTC heaters. 2 small ones in the ducts and one larger one inside the heater core itself. Sadly, they do not come on until the engine temp rises which makes no sense. I added in a manual bypass so I could have at least a little heat in my PHEV when running electric-only.

I also agree; a block heater is the best way to achieve fast warmup. Combine it with grill blocking and it's much more effective.

Also: be warned that if you install a circulation heater, the 3-way valve shuts off the heater core when you shut down the car, so you either have to plumb a different line, or add a circuit to move this valve.

 

Our Prius are different here in UK we don't have the 3 port valve for the thermos so it is straightforward once you worked out where to put it.

 

I would assume this turns into a 2-port valve so the heater core (I think you might call this a "Heater Matrix") can be switched off, is this correct? Though it likely is still open if you shut down the car with the heat on. On US spec cars, the 3-way valve always moves to the thermos position which closes off the heater core.