So if the heater works great when the engine is working and blows cold air when it's not running does that mean that something is wrong with the electric coils are supposed to take over heating?

The engine heats up the inside of the car but only when it's running. There's no electrical coils, know what I mean Vern?

BoholMark - your answer puzzles me and here is why: Last night I read part of another question about the heater system in the Toyota Highlander Hybrid and one of the answers they received spoke about an electric heater system. As a matter of fact here's what they had to say about it - FordNut answered about a week ago - Yes, dandyoun is right. The hybrid uses engine heat, just like any water-cooled car, to heat the cabin. But in the hybrid, there are electric heating elements in the heater core, to help hold heat when engine is not running and car moving. Also a ceramic-shrouded electric heat element in the dash for defrost, but still, it will take a few minutes. These electric heaters draw a lot of power, and operate off the same batteries and generating system that powers the car, and will be heated for only a short time if engine is not running. Regardless, there will never be instant cabin heat - This is why I asked about the heater core system. So if you are telling me there is no electric heater core system then can you help me understand why when I'm driving and the actual gas engine is operating I have heat and all of a sudden there is no heat and cold air was all that was coming out (almost like the A/C was on). I looked and notices the suv was running on electric only. So if I'm no a long trip and the heater system is fluctuating between hot and cold, then that could be a pretty miserable trip. So do you have any idea why it keeps going from hot and cold? Also any idea of how to keep it from going from hot to cold so the temp will be a little more stable? Know what I mean?

LOL. "Know what I mean Vern - it works because its from Newhart and your name is Vern! Classic. Anyway, I play an expert on TV, and it sounds like you took offense to the first answer. Here's where you're misunderstanding -- The "coils" offer supplimental heat when the gas engine is "off" as in, the electrical system is propelling the vehicle and the gas is coasting. When that happens, there is no engine heat to blow into the car (that's how the heater works, its just the waste heat off the engine block) so the coils activate to take over the load. They are able to recharge by starting the engine for energy and by taking brake regeneration power. But they would not work when the car is actually "Off". Because there is no gas engine running to recharge battery. Otherwise the heating elements would completely drain your juice in a matter of minutes. Since a regular car does not heat up unless it is on, the designers of the hybrid system probably reasoned that there was no need to fully drain the battery to provide 10 minutes of heat when the engine was off. (In other words, you need to turn on the car, and expect the gas engine to kick in if you are using the heater while idling. If that's not happening, then you have a completely different problem.)

Upon rereading the problem, it sounds like a different problem. There should probably be heat coming in when the car is "on" but the electric is the propellant. Hope you got it fixed. Let us know what it was and how much it cost!

Vern, did you get it fixed? And if so, what was the issue and how much was it? I drive an 08 Camry Hybrid that does the same thing. Heat works great while driving around, but as soon as I come to a stop or park (when car goes into E mode), the heater starts blowing cold air. I live in Alaska - this is NOT acceptable!!

I am having the same problem! I have not seen an answer yet. Trying to avoid going to dealer and paying tons of money.

Jen17969 did you figure it out on your car? we have an 09 Camry Hybrid and it is doing the exact same thing and we also live in Alaska.

Josh, no answer yet :(

I'M AT WORK BEFORE THE HEAT STARTS WORKING ON MY HYBRID HIGHLNDER. IT TAKE AT LEAST 15 -20 MINUTES BEFORE THE FAN GOES ON.

Alright guys and gals I felt like an idiot on this issue. My car is now fixed but it cost me almost $500 from the dealership. Don't worry you can do it yourself for a fraction of the cost. Because it is a hybrid I didn't know that there were two different reservoir tanks for coolant. I just looked under the hood and saw the "hybrid coolant system on top". The main engine coolant was tucked away on the passenger side and was nearly empty. So they flushed my coolant system and heater works great. I would have done this myself had I known and had a heated garage to work in.

Yep. My main coolant reservoir was bone dry. Filled her up and I have heat again! Cheap and easy fix. Cant believe I've gone 5 Alaskan winters with intermittent heat LOL

It sounds to me that the issue might involve either low coolant or air being trapped in the cooling system which would need to be bled out. It's a pretty easy system to bleed out the air actually. Just run the car with the radiator cap off. Try to be on somewhat of an incline to let physics push the air bubbles out faster. What happens if there is air trapped in the coolant system is that air gets trapped in the heater core and does not allow the coolant to pass properly through. So when you are driving and pressing on the gas the air bubbles are being moved and circulated. But if you come to a stop and the air bubbles are in the heater core then it is going to significantly reduce the amount of heat able to flow to your heater vents. Meaning if you are relying on the electric heater to do its work and you are not moving in the car the air bubbles will most likely be restricting the flow. Make sure you have enough coolant! And make sure your coolant system is bled of air. This usually solves almost any heating problem unless it comes to a leaky hose completely clogged heater core or something that needs to be replaced

I have a 2018 Toyota Highlander Hybrid that had the same issue since new in Mid-2018 where the cabin heater worked fine when engine was running but it immediately turned to cold air when the engine went into EV mode (engine off and running on batteries). We only got thru 2 prior cold winters by immediately turning off cabin fan when we went into EV. So after complaining to dealer many times thru 2 winters I think they "finally" found the issue. My car has a heater electrical pump that is to turn on in EV to recirculate the hot engine coolant through the not-running hot engine (to stay warm) and then through the cabin heat exchanger for cabin warmth. The dealer finally called the Toyota tech center who said to check see if the special pump was plugged in - it was not!! Guess they have run into this before. Go figure - unplugged since new 2 years ago. No wonder we had no heat; we were seriously considering trading the car off. It now works!! Good luck. Cars used to be so simple back in the 50's and 60's.

Also in Alaska, I've had the same issue. However when I topped off and burped out the air in the system I still had an issue. The heat started working but only on the drivers side! Nice warm heat on the drivers side but bone chillingly cold air blowing on the passengers side. Any idea whats up with that?