Ok guys i have been having this problem for quite a while. I bought the car about 6 months ago and the heater core went a few days after i bought it. I had the heater core replaced and when i picked it up the heat was great for about a day. The heat would come and go , usually when i was driving for a while i would get nothing, then i would shut the car off and go into the store or something and when i would come back out and start the car i would have heat again, then it would go away. This happened all the time, sometimes heat sometimes no heat. So i'm driving to work 1 day and bamn!, the top radiator hose blows off, i bring it back to the place [a radiator shop near me] that did the heater core. After lookin at the car he tells me i need a radiator because the neck where the upper hose attaches to ,is gone, there is only about a inch of neck left for the radiator hose to attach, he also says this is why i'm getting no heat beacause it is sucking in air. They change out the radiator and again when i pick it up the heat is great. Again that lasts a couple days, i call him and he say the thermostat might have peices of the neck that broke off stuck in it and it is keeping the thermostat open. I change the thermostat today [nothing stuck in it but some sealant] I start the car and let it warm up and again no heat, luke warm at best. I do the thing to manually open the heater core by pressing the off button then the defrost and so on like i read at motorvate, i hear a trickling of fluid go in under the dash and i get heat for about 2 minutes, i drove around and again the heat goes away. I am thinking the heater core is either messed up or installed wrong, what do you guys think? Do you think it could be something else?

Sorry for the long expanation but no heat in 5-6 degree weather really sucks!

 

sounds like your coolant is low, add coolant... try that

 

Coolant level is fine, that's the 1st thing i checked.

 

I lost a lot of heat after changing my thermost, after some reading I found out that if air got into the system when you were flushing the coolant to change the thermostat, then it would take some time for that air to be worked out of the system and restore full heat to you.

this happened to me, I guess air got in the system, and it had little heat unless it was on the hottest, after a month or so my heat came back full force, and works on cue (as long as the car is warmed up).

 

well sorry for you man, but this is totally off topic...well sort of...but i have no heat at my house...and damn its cold in here......

 

you should relax in your car where there is heat

 

Turn on the car, run the heat on full blast in the car (full hot, full fan) and let it run that way until the car is warmed up fully, you can go for a drive if you like.

By this time the thermostat will have opened and the heater core's coolant will have been used to cool the engine as well.

Now go check the reservoir and radiator for proper levels, being careful not to get burned and add fluid as needed.

Also, check your radiator cap, it should be at least 16 PSI, it says it on the cap. You may need a new one as it may be allowing air to leak into the system even IF all fluid levels are adequate.

 

There is a valve that controls the flow of coolant into your heater core. I believe it's located on the fire wall. That valve is most likely sticky or clogged. When that happens, very little coolant will flow through the heater core resulting in luke warm if any heat. You can manually open it and get all the heat you'll ever need until you replace or fix it.

 

It's funny you mention that because i remember the mechanic messing with that when my heater core went and he said i manually closed it so no coolant would run to my heater core.....hhhmmm i wonder if it's still closed, although i can stll hear a very small trickle every now and then running under my dash.

 

Humm, im gona take a look if my Moms quest has one of these valves, her car has no heat and i cant figure out the prob.

Any details on how this valve looks?

 

Ok ,i just checked that linkage and when i put the a/c on it closes all the way and cold air blasts out, wheni turn the temp all the way up it opens but it looks like only 1/2 way because i can manually open it more. 1 other thing is that when i do the thing with my auto climate control to manually open the heater core [push and hold off, push + heat 3 times ,defrost 2] the linkgage opens more then it does normally and i get really hot air. Once i shut the car off and turn it back on again the linkage only opens about 1/2 way again....strange! Now i am assuming that when that thing opens all the way it is opening the heater core valve and allowing coolant to flow in at a much greater rate and when it's only 1/2 open there isn't enough hot coolant goin in there to get a decent omount of heat, does this sound right? When i feel the hoses running to the heater core they are very hot, so why still luke warm air till i open the heater core by doing the "Auto climate control thing"?


Mine is in the middle of the firewall, right on top. The hoses that run to the heater core are right under it. It has a cable that runs through the firewall to the heater core? I guess and there is some linkage with a spring on it.

 

OK, sounds like we've found the problem. Now you need to figure out why the system isn't opening the valve all the way. There may be a sensor thats gone bad in the system. I have no idea how to troubleshoot the auto climate control and the Haynes manual doesn't give any help either. If you bring the car to Nissan and tell them exactly what you've found, perhaps they can diagnoss the system with their tools and get it working correctly. Perhaps somebody with a Factory shop manual can look up the system and guide you. There was a thread way back that had a write up on troubleshooting the system, displaying all the sensors values ect... Try searching for that, it could help you out.

Your definately on the right track, that valve has to open all the way in order for the heater to blow hot air.

 

Same with my car, heater doesn't blow hot air (only warm air). I guess I'll also look for that valve thing and see what the FSM has when I get home

 

I had similar stuff happening, ended up just being a stuck open thermostat. Warm/hot when standing still or going slow, but on the highway or driving constantly engine temp guage just reached the C mark.

You said you changed the thermostat? Or did you just check it?

 

No,I changed the thermostat. I wondering if the valve that needs yo be open is right underneath the linkage i see or is it at the end of the cable that runs through the firewall?

 

Bump for someone who knows what I have to open all the way.
Again this morning lukewarm all the way to work ,about 20 minutes of driving, it's about 15 f and i can't even defrost my front windsheild because i have no heat, any help would be appreciated.

1. Where the linkage is [with spring and clip] do i detach that cable that runs through the firewall and turn the valve/lingkage all the way to the left to have it wide open?

2. Do i need to pull on that cable that runs through the firewall to open the valve all the way?
I'm not sure where that cable runs to or what it does.

Does anyone know what controls [I know iot's the auto climate control] but is there another sensor that tells it how much to open or close? Is my climate control bad?]