grill blocked, no heat in cabin??!!

Fresh air enters the cabin via the windshield cowl area. If you open the hood and look at the cowl you'll see openings that allow the air to enter.

Make sure that the recirc/fresh air button is set to allow fresh air to enter. If it is and you aren't getting fresh air flow, then maybe the door that allows fresh air to enter is stuck.

 

Hi Lextoy,

You are probably aware of this, but maybe not. The Prius climate control computer will not run the fans, until the engine is warmed up a little. Then it automatically ramps up the fan, and hot air starts to flow.

This is a common thing that is done manually to. Running the fan when there is no heat, makes for a colder wind-chill in the car on a cold morning.

As others have elluded too, the vents for fresh air, on the passenger side of the cowl can become covered with snow, which then can be reflowed into an icy mix, blocking off those passages. Use a snow brush bristles down, with a hammering action to push the icy mix through the cowl duct wire mesh screen, after removing any over-lying snow. If the bristles on your brush are all curled up and distorted from use, this wont work. The bristles need to be straight and present a pointed end to the vent.

 

From a long-time grille-blocker: Your grille blocking should, if anything, enhance cabin heat by accelerating ICE warm-up. So I agree that something else is amiss.

 

This thread made me realize that I do not understand the specifics of cabin heating from engine heat. Is air surrounding the engine passively heating up and being drawn into the car cabin, or is engine heat transferred to air that originates elsewhere, and then the air passed into the cabin ?

OP: How much power do you think you are saving ?

 

The Prius cabin heating starts off with the same concept as nearly any automobile with a "water-cooled" engine: hoses provide hot engine coolant to a heater core located within the HVAC system in the passenger cabin. The heater core produces heat. A blower assembly circulates air past the heater core, heating it up, so that it can flow through the various HVAC ducts.

Since the Prius engine turns off from time to time, a couple of refinements were added to this basic design. 1) an electric pump is used to continue the flow of coolant through the heater core even when the engine is off. 2) a couple of PTC electric heaters supplement the heat output from the heater core.

The original VW Beetle with an air cooled engine had a cabin heating concept which required air to be drawn from the engine compartment. This was a very unsafe concept because all sort of noxious fumes including carbon monoxide could enter the cabin. Just one of many reasons why that vehicle would be designated a death trap given today's standards.

 

Is it this blower that is turned off when the car operator sets the 'fan' to off ?

Thanks for the education!

 

Yes.

 

hmm. So is OP inadvertently turning on the electric heaters by turning off the fan but cranking up the heat setting ?

 

No block heater?
PriusChat Shop : Toyota Prius Engine Block Heater [Prius EBH] - $59.00
If your parking situation permits you to run one, then do it. Put a timer in line, let it run for 1.5 - 2.0 hours prior to departure e/ morning, and you're good to go. Higher winter mpg's AND quicker heat.

 

Has anyone considered that due to the very low wind drag of the Prius shape there is little pressure in front of the car to push air through the vents without the fan to assist?

 

I was surprised when I first learned of these supplemental electric heaters (on this forum of course) and I may be in for some more surprises now, but I thought the electric heaters only came on when the engine temperature was below some value (unknown to me) and when in defrost mode. Do they also work under high heat settings as well?

 

Per p. BE-108 of the 2004 Prius New Car Features manual, here are the rules for PTC heater operation:

When the hybrid system is operating (READY), and the blower motor is turned ON, the A/C ECU turns ON the PTC heater if the conditions listed below are met.
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Heater core integrated PTC Heater​

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Air outlet is in the FOOT, FOOT/DEF or DEF mode.​

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Engine coolant temperature is below specified temperature.​

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Ambient temperature is below specified temperature (DEF mode).​

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Tentative air mix damper opening angle is above the specified value. (MAX HOT)
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Footwell air duct integrated PTC heater​

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Air outlet is in the FOOT or FOOT/DEF mode.​

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Engine coolant temperature is below specified temperature.​

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Tentative air mix damper opening angle is above the specified value. (MAX HOT)​