All of a sudden the heater in my max will only get hot if the car is moving. If I'm moving everything is fine, but if I stop at a light I'm freezing!! Anyone else ever have this problem? What should I have checked first?

 

Is this on all settings , floor, face,defrost , mix?

What about all fan speeds 1 - 4?

SuDZ

 

Check the water level in the radiator(only when cold!). Next is the thermostat. Then maybe it's something the heator controls.

 

Jeff, do we have heater cores? I have replaced them in older cars but don't hear about them much on here... is it popssible his could be shot?

SuDZ

 

This problem is occuring on all settings. I had the water pump and the thermostat replaced a few months ago as well. I'll check the water level in the radiator a little later. Could it be a radiator problem?

 

\First thing first check your coolant level.
In most cars the thermostat does NOT effect heater functions... More or less the deal is as the water pump turns it forces hot engine coolant into your heater core. If the core failed then you would smell coolant inside the car but the heater would work. To my understanding though the heater core does not always get heated water. The heater core shares the box with the evaporator core. That being said there must be a valve that allows heat in or does not allow it in. I would suspect this item is what is screwing you. I bet if at a traffic light and you reved your motor that the heat would work.. The only other thing I could see here is the H20 pump was not installed right and water is not getting forced around like it should.

 

Go to hardware store, and get a space heater. Then buy a power inverter and plug it in! Feel the HEAT!

 

I'll check these out. Thanks guys.

 

Yup, we have heater cores. Like you said, they never ever seem to go bad. They are either built very very well of some un-corrodable metal, or the heating system shuts off radiator flow to the core when not needed.

DW

 

If I'm not mistaken, our Maximas isolate the coolant from the heater core until the coolant has reached a certain temperature, the reason mainly being to speed up the engine warm-up time and improve emission levels at cold start.

If you have a FSM, check the system and see if you can identify whether there is a solenoid that controls the coolant flow to the heater core.

Edit: In my opinion, this explains why it takes forever for the heater to start warming up the car in the winter time. In my Max, the heat starts immediately after many many minutes, as if a valve had indeed opened up. Maybe?

 

I checked the FSM. There seems to only be an air mix door. It controls the flow in the cabin. The heater core seems to be a regular old school heater core, with coolant constantly flowing thru it. In fact, there's a diagnostic section at the beginning for in-sufficient heat. If you find that both hoses to the heater core, the inlet and outlet hoses, are warm, then it says to replace the heater core, and it doesn't show you how Pages and pages are dedicated to the AC compressor, but the heater core gets very little detail. It's as if Nissan was saying "if you have to replace your heater core, you're f**cked." Tearing apart that dash will be no fun at all.

DW

 

Well if you have to do this.. I think it is inside the box with the evap core.. you have to take apart the glove box are and disconnect the A/C system..(you will loose all your freon) you can then pull the heater core/ evap core into the inside of the car.. open the box replace the part and install in reverse.. vbut you will have to buy new seals for the evap core connection and get it vacuumed and recharged..

 

How much do you think it would cost to have this done?

 

Your problem is simple. It's low on coolant. The reason it warms up while you are driving is because when the engine is turning faster, it is circulating what little coolant it has left, and when you stop at a stop light or something like that, the engine settles down and the coolant settles.

 

Yes, I should have said this earlier. Replacing your heater core is a very very last resort. The diagnstic I mentioned before has the heater core replacement as the last thing. Before doing that, check your coolant, thermostat, etc. Once you have verified that everything else is in perfect working order, THEN the heater core will be suspect.

DW

 

Thanks everyone.