no heat in cabin

There are a number of possibilities. Air bubble in heater core is most likely. Have you kept up with the coolant level in the reservoir? If you have to keep adding coolant, you may have a head gasket issue waiting for you.

Since you have 100k, I would consider changing:
- The Engine Coolant
- The Inverter Coolant
- The "Transmission" fluid.

Be sure that official Toyota Fluids are used, if you pay somebody to do it, or you do it yourself. The Toyota pink coolant is not the same as the universal Japanese red/pink coolant you can buy at Walmart. Just shop around at different dealers, and you can find Toyota coolant for about $21 gallon. Some better auto parts stores also sell the official Toyota Pink coolant.

Getting all the Coolant out is impossible, since you can only buy the pre-diluted coolant. You need to get as much of the coolant out as you can. I put my 2013 v front up on jack stands, and then drained from the radiator in the exhaust pipe. That becomes the lowest point in the system with the front on jack stands. I opened up the hoses at the bleed valve, and I got 90-95% of the coolant out. You need to run the engine in "Maintenance mode" until the radiator fans run to properly burp the system.

I would also recommend changing the plugs, but save that for when you have the EGR, EGR cooler, and the EGR Passages in the Intake manifold cleaned out. You have to remove the whole windshield wiper assembly to get to the plugs, so that makes plug change and EGR cooler cleaning at the same time as the logical thing to do. Again, buy the plugs from the dealer. They don't cost that much more than the ones on Amazon, and you know they will last another 100k.

For more info: Search for the Nuts about Bolts video for changing a Gen 3 engine coolant.

My fear is that you have the beginning of a HG leak, and that there is a bubble in the heater core. I forget if the 2012 V has the self bleeding valve for the engine coolant, or not (the 2013 does).

 

Before doing anything, I would look for any trouble codes. You can get those from the HVAC very easily without any kind of scan tool. Just hold down the AUTO and FRESH/RECIRC buttons while turning the car on. Look for two-digit codes in the usual HVAC display.

 

Have you driven for more than 1/2 hour?
Have you replaced the cabin air filter?
Have you checked the fuses for electric part of the heater?

 

Have you taken the five seconds needed to get the trouble codes?

 

Are you saying there's trouble codes logged for heater even if there's no dash warning lights?

 

Absolutely. Can't think offhand of an HVAC code that does light dash warning lights.