I am working on a friends car, its a 2002 Altima SE 2.5L Automatic. I would appreciate any input from anyone who has troubleshot such problems.

Problem: Heater is not always blowing hot air when heat is on. What seems wierd to me is it never overheats. Water temp.stays in the middle.

Here is what I have found:
1) Both hoses on the water control valve housing are hot (return to radiator and inlet to heater core).
2) Heater core outlet line is warm at best (whether hot air is blowing or not). Inlet hose from WCV housing to heater core is hot as stated above.
3) Bottom radiator hose that goes to thermostat is warm at best.
4) System is full of coolant and there are no leaks anywhere.

Because the thermostat hose was not hot I thought it was stuck open, so I changed the thermostat. Made no change at all. I will change the WCValve next and see what happens. It seems wierd that sometimes warm air will blow but the core outlet line never gets hot like the inlet line (possibly blockage in core). Seems to me as if there are multiple problems but no overheating (I have never seen this before). My experience is these problems always cause overheating! Also the fan motor works on all speeds and vents blow per what setting is selected.

Questions:
1) Shouldn't the bottom hose be hot?
2) If the water pump shaft was sheard therefore not pushing coolant wouldn't the engine overheat?
3) How could warm air blow sometimes but the core outlet line does not get hot?

What am I not grasping here? Any ideas on possible causes would be greatly appreciated!

Thanks,
Pedro62

 

sounds like the blend door acuator is operating that moves from the evaporator from the a/c side to blow cold air, and the heater core side to blow hot air is malfunctioning. that valve that you want to replace wont fix it. could be caused by bad temprature control switch, blend door acuator, or worst the blend door is broken.

 

Thanks HXC_Nismo,

I thought that might be a possibility also but what makes no sense to me is this. Why is the core outlet hose so much cooler than the inlet ( I realize some of the heat is dissipated through the heater coil, but I would not think the difference would be so much), and why is the outlet hose from the radiator so much cooler even when at idle with no airflow through the radiator and no cooling fan running. I have never experienced this kind of temp. difference with any other automobile so that has really messed with my thought process. If that is the problem then I guess there is some type of rheostat or motor that controls the door and will it be necessary to remove the core shroud to repair? I will look at the manual and see if it gives some troubleshooting how to from easiest to hardest.

Thanks again and any advice on repairing the problem would be most appreciated!

pedro62

 

I have had problems with the water control valves before, so you may just have that as a problem. Did you bleed the system out properly?Those motors were very picky on their bleeding procedure (almost as bad as the quest ). In fact Nissan even released a tsb regarding the proper way to bleed the system. It involved jacking the front of the vehicle off the ground, by like a foot or better. You would have rig the rad cap to stay open at all times, and make yourself something similar to an "I.V." bag out of a plastic bottle. Fill the bottle with coolant, and proceed to bleed.

 

Did you ever figure this out? I have a 2001 Sentra with the same problem 1.8L I cannot figure this out for the life of me. Sometimes it overheats, sometimes it doesn't, sometimes I have cabin heat but not always.
Thanks

 

I think the heat is not enough to blow up some heat... but it should be I think the problem would be on the engine, it has a weak capability to support all the functions of your it your car a used one or new?

 

hey
the same problem goes with my 2002 Altima SE
my friend was suggesting me to get it serviced
do i really need to do so??

 

I also have a 2002 Altima and just recently started having the same problem. This will be the second winter I’ve gone through with this car and never had trouble with it until last fall. Now, not only does it blow cold air when at a stop light or idling, I also have to drive with my defroster on or the windows fog up. I took the car to the dealer a couple months ago, and the service manager in so many words told me I was crazy. I called Nissan’s Customer Service (1-800-Nissan-1) and was told they’ve never before had this complaint about the heat. I have a friend with the same car and she’s never had trouble. Anyway, I have an appointment next week with another dealer’s service department…hopefully they know something.

 

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known as "Burewala Express".

 

Hey bud, sorry to hear that, I haven't picked up the parts to do my head gasket yet so please let me know what the dealer says. I'll let you know what I find as well.
Thanks