Why is my heater not working?

It sounds like the blend door actuator is out but to be sure this guide will help with the actuator location in the diagrams below

https://www.2carpros.com/articles/car-heater-not-working

Code 12 - Passenger air mix door open/short/out of limits.

I have included both auto and manual systems. Check out the diagrams (Below). Please let us know what you find.

The heater hose connector to the heater core broke, I fixed that problem, replace the coolant, truck has no heat. when idling, the temperature gauge stays in the middle, when I go to drive it, the gauge goes way up and no heat.

Hello,

It sounds like you have an air pocket in the cooling system. There is a special way you need to fill the system. here are the instructions. You may be able to purge the system by raising the back of the truck using a jack, then try raising the front while running.

https://www.2carpros.com/articles/car-heater-not-working

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

My heater is fading hot and cold air when turned on. Sometimes the heater will hear up for 10-15 minutes and cold and sometimes it doesn't heat up at all. Do my heater needs to be replaced? If so, what is the estimated cost to replace? Thank you for your time.

LD

I have the same issue on a 2005 SE 4X4 with 80K. I don't see any replies here, have you gotten the problem diagnosed yet?

No, nothing yet. Still searching. As much as I don't want to, I might have to take it to the dealer. it's getting colder and colder :(

I too have a heat problem--heat works fine when engine is revved. Not sure its a water pump issue of vacuum issue. Also have had rear diff replaced.

Mine is doing the same thing... runs real warm when revved up or accelerating, but cools right off when idle or coasting...

our pathrinder is going the same thing, driving the heat works, but slow down and the heat runs cold.

Our 2006 is doing the same thing, heat only works when the vehicle is moving or reveved up. Wish someone had an answer.

called to take my suv in and described the problem, and they said that it sounded like the heater core needed back flushed. If it works, will let you know.

I have an appointment on the 18th for mine. They told me to check the antifreeze level, I did and it was fine. They claimed that it could have a air pocket just before the thermostat. I think this is some kind of Nissian design problem, we should check deeper into it. I will post my results from the dealer.

place that i took our SUV to, said that Nissan vehicle were well known to get sludge build up in the anti-freeze and that the heater core would need to be flushed. But ours had a leak in the back heater part. he said that a piece of steel runs from the back of the vehicle for the heater all the way to the front. When nissan built it they put this part on and then put on the body. so the only way to get to they whole thing was to lift the body off. which is expensive. I just had them cut off what was bad and replace just that section. So my anti-freeze was taken all out then replaced. The hardest job they had was getting the air bubbles out.

So did this solve your problem with the heater not being hot unless the vehicle is revved up?

yes, it did work. Haven't had a problem yet. So it may have been both things that were done that made it work. Emptying the anit-freeze got the sludge out. and fixing the holes in the line for the back heater.

Ok my dealer did a pressure check on my coolant system. He said I have a manute leak on my heater core where the tubes hook to the core at the firewall. He said that it is letting air into the system which is causing the problem with the heat. Cost to repair $500.00.

Ok I took mine to another dealer, becuase I thought the first Dealers quote was too high ($500.00).

They replaced all of the plumbing at the firewall where the heater core is. That fixed the leak and my heating problems. Total cost. $315.00

my car heater will only work when I push the gas. It will not work when idling. help!

Check if low on coolant
check heater core if plugged and it may need to be flushed

I noticed that the heater was blowing cool air. I raised the temp on the dash to 85 degrees and still no heat. Heater core or thermostat and how do I tell which it is? I am not mechanically inclined but I can follow directions. Is there a way to rule out whether it is a heater core or a thermostat problem?

Is the engine running at a normal operating temp? Also, when the heater is on high and the engine has warmed up, are both heater core hoses getting hot?

Air blows but only cold, it does not get hot at all. We have flushed the system and coolant levels are good. The vehicle runs at normal temperature. We have no idea what the problem could be. Any ideas? The vehicle's year is 1999.5.

Hello,

It sounds like the temperature blend door actuator is not working which will cause the air door not to move allowing the hot air inside the car. Here is a guide to help you see what you are in for when doing the job.

https://www.2carpros.com/articles/replace-blend-door-motor

and

https://www.2carpros.com/articles/car-heater-not-working

Check out the diagrams (Below)

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

AC works fine but I cannot get any heat.

No heat could mean coolant is not getting to the heater core or the air mix vents are not working correctly. Start with a flush of the heater core to check if it is clogged.