I bought a 2007 Maxima with a 3.5 this spring. Now that it's cooling off, I noticed that there is an issue with the heater. The a/c works great. I see many topics about no heat at idle. Mine is almost opposite. I get a little bit of warm air at idle. As soon as I start driving, the air gets cold. The problem isn't with the hvac. The heater core only gets warm, not hot. I've performed the burping fix that I found online, where the front of the car is lifted and a burp tank is hooked up to the overflow line. I took it to a radiator shop. They replaced the thermostat, purged the cooling system and did the same burping fix that I had done. Still doing the same thing. I have about one week before the frost hits and won't be able the drive this car. Please let me know any suggestions you have. Thanks!

 

Get your car to operating temperature. Turn on the max temp/low fan for heating. Open hood and feel how hot the (1) inlet and (2) outlet hoses are to the heater core. The hoses should feel about the same temperature to you. If one is hot while the other is noticeably cooler, then you have a blockage in your heater core. If that is the case, then you'll have to flush it.

 

Thanks for the reply TDGrant. When the engine is at operating temp, the outlet is about the same temperature as the inlet. Neither are as hot as the elbow at the thermostat. Not even close. The radiator shop tested the cooler and there was little resistance in flow.

 

Ah, then I wonder if it is a blend door.

 

The "air-mix" door in particular.

 

Thanks. Great diagram. I took the motor off and the turned the door manually. It moves freely. Air temp changes minimally when the engine is warm. The motor seems to have full motion when turning in my hand. I have it at a shop now. They've done the same things that I've done, with the same results. The problem is hot coolant not getting to the core. They're trying another process to purge the air from the cooling system/heater lines today. I'll update when I have answers.

 

I would have been scratching my head forever on this one. I took it to three different shops before it was solved. There was a blockage in the coolant crossover pipe. My Nissan dealer found the issue after replacing the thermostat, because the thermostat didn't solve the problem.

 

Congrats, Chris!

 

Upload a pic of the pipe they replaced when you have a moment. Then others on the forum will have a starting point if they ever have an issue like yours.

 

The dealer was very vague about where the blockage was, as it seems to have several passages.

 

Wow...cool and certainly good to know.