No Heat

[slickroger]

Winter is coming and I have no heat

When i turn on my heater I only get cold air it doesn't seem to warm up.

Who here knows whats wrong?
Modified by slickroger at 12:31 PM 9/30/2009

[Pwnin O'Brien]

It just sounds like your air mix door motor is not functioning properly. When you change the temperature from one extreme to the other does the temperature change at all? If it does change a little then maybe the air mixture door is blocked. If it doesn't, then you may need to replace the motor. Of course, your climate control unit may be malfunctioning (which I would doubt since all of the other functions work).

The service manual has a pretty lengthy trouble diagnosis on the auto A/C system.

[slickroger]

where is this and can I simply just unblock it

[godofspeed666]

Make sure your car is warming up first. Also check to see if you have a heater control valve and that it’s working. and also make sure you blend door is operating. some things that can cause the blend door not to operate switch on the dash, vacuum line off if its vacuum operated and also vacuum solenoid and if its electrically operated that the actuator is good and getting the right signal.

It would be strange if the blend door is not operating because engineers default is heat and defrost. Not saying its not possible but not my first choice

I would check and see if there is a heater control valve and make sure it’s operating.

[Pwnin O'Brien]

where is this and can I simply just unblock it

Well, I don't think it's too easy. The air mixture motor is located behind the heated seat switches on the heater unit. To ensure proper operation of the air mixture door probably requires removal of the heater unit, which is no simple task.

There are a few things I would recommend before doing any major dis-assembly. Once your vehicle is warmed up, check the temperature of the heater inlet/outlet hoses coming from the firewall into the engine bay. These hoses may be a bit difficult to get to since they are behind the engine. This will ensure that your heater core is actually getting coolant and heating up. Sometimes an inoperable thermostat (the second thermostat located on the rear of the engine) or air in the cooling lines will prevent the heater core from getting warm.

If you have checked the hoses and they get hot, then your next step would be to check the operation of your air mixture door. Remove your center vents, the trim which surrounds the A/C controls and radio, then remove the radio. If you look down into the open cavity you should be able to see the air mixture door motor. Turn your vehicle ON (without actually starting the vehicle). Change the temperature from one extreme to the other and see if you can hear or feel the motor engaging. If it is engaging, then the door may be blocked or may need to be adjusted. If it is not, then either the motor need replacing or the HVAC controls are malfunctioning.

Make sure your car is warming up first. Also check to see if you have a heater control valve and that it’s working. and also make sure you blend door is operating. some things that can cause the blend door not to operate switch on the dash, vacuum line off if its vacuum operated and also vacuum solenoid and if its electrically operated that the actuator is good and getting the right signal.

It would be strange if the blend door is not operating because engineers default is heat and defrost. Not saying its not possible but not my first choice

I would check and see if there is a heater control valve and make sure it’s operating.

The air mixture door is electronically controlled. If the air mixture motor failed while turned to the cold temperature, then the door would remain in the cold position.

[slickroger]

Well, I don't think it's too easy. The air mixture motor is located behind the heated seat switches on the heater unit. To ensure proper operation of the air mixture door probably requires removal of the heater unit, which is no simple task.

There are a few things I would recommend before doing any major dis-assembly. Once your vehicle is warmed up, check the temperature of the heater inlet/outlet hoses coming from the firewall into the engine bay. These hoses may be a bit difficult to get to since they are behind the engine. This will ensure that your heater core is actually getting coolant and heating up. Sometimes an inoperable thermostat (the second thermostat located on the rear of the engine) or air in the cooling lines will prevent the heater core from getting warm.

If you have checked the hoses and they get hot, then your next step would be to check the operation of your air mixture door. Remove your center vents, the trim which surrounds the A/C controls and radio, then remove the radio. If you look down into the open cavity you should be able to see the air mixture door motor. Turn your vehicle ON (without actually starting the vehicle). Change the temperature from one extreme to the other and see if you can hear or feel the motor engaging. If it is engaging, then the door may be blocked or may need to be adjusted. If it is not, then either the motor need replacing or the HVAC controls are malfunctioning.

Alright man I did everything you said, my car is apart and the motor seems to be working. The arm moves pretty far when i change temperature from the two extremes. So the door is opening and closing I don't see how anything can get stuck in there considering i cant see the door itself moving.

I might try to remove something so i know the door is functioning for sure, but does this look like i will be replacing my heater core?

[Buzzman]

You didn't mention if you checked the hoses.Are the heater hoses at the firewall hot?From everything you described, I'm guessing heater core.If one hose is hot, and the other is still cold, then you probably have your answer.A reverse flush is something I would try before going to the trouble of removing the core.Keep us informed.

[slickroger]

after running the car to optimal temperature one hose is ice cold and the other seems to be hot but not super hot like I expected. I can grab the hose and hold it.

Is this normal am I looking at a heater core replacement i would like to buy the part tomorrow and get it over with?

Thanks everyone for your help

[Pwnin O'Brien]

after running the car to optimal temperature one hose is ice cold and the other seems to be hot but not super hot like I expected. I can grab the hose and hold it.

Is this normal am I looking at a heater core replacement i would like to buy the part tomorrow and get it over with?

Thanks everyone for your help

Hmmmm, that doesn't sound right at all. You're talking about the heater core hoses, right? These hoses are dead center with the engine, and run between the firewall and the rear of the engine. Neither of these hoses should be ice cold, they should both be the outside temperature if not hot. These hoses should get as hot as any other cooling hose under the hood. You don't want to mix the evaporator hoses with the heater core hoses, both come from the firewall.

If you did feel the correct hoses, and neither is hot, then there are a couple of things it could possibly be. If one hose is warmer than the other, the service manual says you need to check/replace your thermostat. This doesn't really make much sense to me since a bad thermostat would be indicated by a hotter-than-usual coolant temperature. If both hoses are warm then you need to flush the cooling system. If that doesn't remedy the issue, then you need to check/replace your heater core.

My recommendation, start by troubleshooting your thermostat. If that doesn't seem to be the problem then flush your entire cooling system thoroughly.

[slickroger]

I very recently changed my rad and thermostat when i had an overheating issue and the truck went into fail safe mode.

so i really think its the heater core and i probably wasn't touching the right hose because it was very easy to reach.

heater core?

[Pwnin O'Brien]

You heater core is located in the heater unit which is located directly behind the center dash (behind the heated seat switches, radio, etc.). Unfortunately, this will be a very difficult item to replace. I'm not too familiar with the replacement procedure of the heater core or heater unit, but I am assuming that this would require removal of the entire dash assembly. Here are a few pictures so you can get an idea of what needs to be replaced and where it is...

The heater core (the part which you need to replace) is in the red rectangle.

The heater core is inside of the heater unit. You can see the location of the heater unit with respect to all of the other parts of the HVAC system in the following pic.

Replacing the heater core is definitely not a project for the faint at heart. This will definitely be a weekend-long job. One thing that I would recommend checking first is to make sure that there is absolutely no air in the cooling system. Air in the heater core can be very difficult to expel and will prevent the core from heating up.

[godofspeed666]

no because if blend door fails as a default the blend door goes to heat and if your selector control fails it will go to defrost position so you can still see when it gets foggy they do this on all cars as a safty percosion.

[godofspeed666]

if you were on the right hoses and they were that cold and the car was at operating temp you need to check and see if you have a heater control valve its located on the entrance side of your heater hoses if that’s not operating then its not going to let any coolant flow throw your heated core.

[godofspeed666]

The reason it says to replace your thermostat is because just about all new thermostats are designed to fail in the open position so the vehicle want over heat. If the thermostat was at fault then the car would either take a long time to get to operating temp or not at all. Again to ensure this is not the case just makes sure your car is reaching operating temp in a normal amount of time.

[slickroger]

my car reaches operating temp in about a min. My rad and thermo were replaced months ago with a full coolant flush.

I am going to try and take that whole heater unit apart today.

[Pwnin O'Brien]

The reason it says to replace your thermostat is because just about all new thermostats are designed to fail in the open position so the vehicle want over heat. If the thermostat was at fault then the car would either take a long time to get to operating temp or not at all. Again to ensure this is not the case just makes sure your car is reaching operating temp in a normal amount of time.

What you are referring to is called a fail-safe thermostat. This type of thermostat utilizes a reverse-spring assembly which pushes the thermostat closed when coolant temperature falls below normal operating temperature (making the thermostats neutral position open); this design prevents overheating due to thermostat failure. The conventional thermostat has a spring which pushes the thermostat open when the coolant temperature is at or above the specified normal operating temperature (making the thermostats neutral position closed); if the thermostat fails to open (roughly 99% of thermostat failures is when the thermostat fails to open) then the engine will overheat, essentially "choking" the cooling system and preventing coolant from flowing into the engine heads/block.

Most automobile manufacturers (including Nissan) do not utilize fail-safe thermostats as original equipment, instead utilizing the conventional spring-open thermostat. More specifically, in slickrogers case, he has had previous overheating. Overheating can lead to thermostat failure by disfiguring the wax contained within the thermostat. This disfigurement can cause the thermostat to fail in the closed position.

Roger has made it clear that he has replaced the thermostat since the overheating incident so we can probably discount the thermostat as being the primary cause of his issue.

[slickroger]

When I had my overheating issue I got code P0217 Engine Overtemp Condition. What had failed was my ECT (engine coolant temperature) sensor located at the rear of the engine. During the process of figuring out what was wrong I replaced my rad, thermostat and flushed the system.

What I am going to do today is essentially try to get to the heater core, but I am going to try to do it so that i can still check to see if it heats up when i turn heat on and try to visually see the air mix door open and close.

Heater Core prices

Part source $238Canadian Tire $238Napa $260Dealer $350Courtesyparts $182

Can anyone from Ontario give me an average on how long http://www.courtesyparts.com takes to deliver Brian, Mikey?

[godofspeed666]

I’m not saying your wrong but I work on cars for a living and I get my ASE's recertified every year and can honestly say that when ever I had a thermostat fail it failed in the open position i guess it was a coincident . But hay what do I know. Good luck and have fun taking your car apart.

[Buzzman]

if you were on the right hoses and they were that cold and the car was at operating temp you need to check and see if you have a heater control valve its located on the entrance side of your heater hoses if that’s not operating then its not going to let any coolant flow throw your heated core.

Good point here. I forgot about this feature. Most cars have it. Even my old '88 Dodge Caravan had a control valve in the hose that would prevent the coolant from reaching the core. (Someone correct me if I'm wrong, but I think the logic behind this is that when the A/C is on, you don't want hot fluid running through the heater core. This would make the A/C less efficient.)Before you rip apart your dash, I would check into this first.OK, quick update: I just went out and checked my truck, and both heater hoses are still warm. (I've only been home about 10 minutes.)Also, I don't see a shut-off valve in the system, so that theory may be a moot point.However, there is a bypass tube running across the front of the engine that would allow all the coolant to bypass the heater core if the core gets blocked.Check and see if it's hot.I still think the first thing you should do is disconnect the hoses from the heater core tubes at the firewall, and run a garden hose through the core to see if you can get any kind of flow. If it's blocked, this may just fix it.You don't have to empty the cooling system either, as the hoses are at the top of the engine bay. You may lose a few drops, but that's about it.

[Pwnin O'Brien]

I still think the first thing you should do is disconnect the hoses from the heater core tubes at the firewall, and run a garden hose through the core to see if you can get any kind of flow. If it's blocked, this may just fix it.You don't have to empty the cooling system either, as the hoses are at the top of the engine bay. You may lose a few drops, but that's about it.

I was hitting reply right before I saw this message. This is exactly what I was going to recommend. You may just be able to flush the heater core and clear the blockage. Removing the heater unit and heater core seems like a real PITA.

[slickroger]

Are these the correct hoses i'm looking at and are those the two I will disconnect to flush?


Modified by slickroger at 5:41 PM 12/2/2009

[slickroger]

If I have the hoses labeled correctly the those hoses are warm after i warmed the truck up and all other rad hoses are at there usually pretty hot temps.

Do i just connect a hose to the top port and flush?

If there is a heater control valve I cant find it on the car or in the fsm I have.
Modified by slickroger at 3:27 PM 10/1/2009

[Buzzman]

I took pictures of mine. I think you have it right.



Both hoses should be warm when the engine is warm.

[slickroger]

they are warm and the bypass is closer to hot

Im flushing the system tomorrow to make sure air isn't the issue if that could be the issue.

than i guess my heater core is coming out?

[fueler]

did you ever check and see if the hot/cold air mix vent is operating properly?

[slickroger]

the door seems to function properly well the actuator works i can see the arm move from one end to the other but i cant see the door itself without removing the dashboard.

[slickroger]

Current state of my dash



Actuator and door lever in Hot position



Actuator and door in cold position


Modified by slickroger at 5:46 PM 12/2/2009

[jsm02cpa]

Roger, I had a blazer that would not get heat to it after a flush. I took it to the repair place, and they wanted to replace the heater core. I couldn't image that was it, and after living with it for a whole winter, decided to take off the heater core hose and run water in it. There was a air pocket evidently, as it worked great ever since.

You indicated you were going to do that, that is the cheapest thing to try, it eliminates an easy problem.

Good luck, this stuff can be a real pain!

[Buzzman]

they are warm and the bypass is closer to hot.I'm flushing the system tomorrow to make sure air isn't the issue.

What happened after the flush?Was there air in the system?Just curious.

[slickroger]

Alright Problem solved.

There was air in the heater core.

I had Flushed the cooling system and tried the heat and it didnt work. Then i took the hose off the heater core itself and ran water through the core, reattached the hose, refilled the cooling system and gave her ago and it worked hooray.

I had also ran all the tests on my climate control unit and it appears my air intake door isn't functioning. So when i press the recirculation button nothing happens, according to all the tests my climate control unit is malfunctioning. Qxxx4 is gonna let me try his unit and that way I can make sure its the unit and not the door.

Do I have an in-cabin air filter? If i do I cant find it

Thanks everyone for the help!!

I got new pics coming more lights and when winter comes im throwing on the new painted stock wheels.
Modified by slickroger at 2:17 AM 10/4/2009