2010 Nissan Frontier cabin heat problem

[pielover88]

My mom's 2010 Nissan Frontier is acting up. It just hit 100K miles, and the cabin heat is totally wonky.

Once the engine warms, the air blowing in fluctuates wildly from super hot to no warmth at all. She thinks it's a temperature sensor or the vent motor causing it, since it varies so much.

It's not that I want to repair the car, but I want an idea before I help her take it to the dealer. Any thoughts on what's going on?

 

[Itsmagic1]

How the engine temp looking? I was going to say the thermostat, but if the engine temp is good, then that's probably not it. It could be the resistor on the blower motor though. If it failed or starts to fail it could cause these symptoms. I'd also check the heater core or the coolant levels, just to be on the safe side.

 

[Drogdealer]

'm guessing heater blend door might be the culprit cos it controls how much hot air mixes with cold, and if the actuator or motor that moves it goes bad, you get that on/off hot air swing thing or maybe a faulty temperature sensor or a low coolant level messing with heat regulation

 

[PuppyMilk]

A failing blend door actuator is likely, but the fact it's so hard to access feels like it was built to fail expensively