# cab heater not working



## 89maximafrommom (Oct 16, 2005)

All functions and modes work. Fan motor works at all speeds,directional modes work,A/C works. Just no heat. Winter is near, please help.


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## nismosleeper (Jan 16, 2005)

89maximafrommom said:


> All functions and modes work. Fan motor works at all speeds,directional modes work,A/C works. Just no heat. Winter is near, please help.


is there any warmth? Turn the heater on, and listen on the passenger side, where a big black box is for the sound of water traveling. Also unhook the two hoses under the hood on the firewall that go to the heater core and run pressurized water through it via a garden hose and make sure that there isn't any build-up in there. Also, when the car is on, and the heat is on, the coolant should run through those hoses, so take one off and make sure that it is flowing, and then proceed from there.


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## 89maximafrommom (Oct 16, 2005)

There is no heat or warmth. I turned the heater on and could not hear any sound of water from the passenger side. I then unhooked the two hoses from the firewall that go to the heater core and ran water through it, the water seemed unobstructed. Next, with the car on and the heat on, I removed one hose (top one) no water flowing (maybe just a trickle). Thanks Tulsa, any other thoughts.


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## adroga (Sep 16, 2005)

Warm up your car until the temp guage hits the middle.

Turn on the heat, make sure the vent switch is off fresh air, and press the recirc button. Now if you dont feel any heat, go into the engine bay while everything is still running and grab the two hoses that run into the firewall(they go into the heater core) and see if one feels hot and the other cold. If so then your heater core is blocked. If you dont feel one hot, then maybe your thermostat is stuck open.

I guess after enough troubleshooting that maybe you might be in line for a water pump replacement if its not functioning properly -> but if its not circulating the coolant properly then y our temp guage would most probably indicate that its overheating.

2 questions:

1- have you done a coolant flush/change recently?

2- are you due for a timing belt/tstat/h20 pump replacement? (if yes, where does the temp guague go when warm? low? middle? high?)

The last thing I can think of is to bleed your coolant system of any air... maybe there are some bubbles in there that are causing the flow to not be smooth and the heat will be quite low.

The bolt is here: www.mattblehm.com/faq/VG_bleeder_screw.jpg

Loosen the bolt a little and run the car until you see a continuous flow of coolant from out of there. If you see nothing come out at first or coming out in spurts then you have some air in the system. Then close it (be careful not to overtighten, I did that and brooke the head off really easily... tighten until you feel a little pressure.... or even buy a replacement bolt for 3$ from nissan and make sure it doesnt break or you are screwed for later...)

Sorry.. long post


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## 89maximafrommom (Oct 16, 2005)

The two hoses that go into the heater core/fire wall both feel warm, but only warm to the extent of being so close to the engine. The top hose from the engine is hoter than the lower one. Q1, full flush and change july/05. Q2, water pump ok, temp. gauge in the middle.
P.S. there is an electrical/regulator/thing/ between the top hose from the engine to fire wall.Could there be a problem there?


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## adroga (Sep 16, 2005)

If you did do a full flush this past july, then I would really suspect that you need to bleed the air out of your system through the bleeder bolt...


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## 89maximafrommom (Oct 16, 2005)

I loosened the bleeder bolt (engine running and warm) and a small amount of coolent came out. then nothing. The coolent seems to stop at that 'gizmo' thing on the upper hose between the engine and the firewall. Very hot before then luke warm after.


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## adroga (Sep 16, 2005)

If nothing is coming out then you have some major air in the system...

i think you might need to leave it open a while until there is a continuous stream coming out...


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## 89maximafrommom (Oct 16, 2005)

I will lossen the bleeder bolt again (tomorrow). Is there any specific a/c mode that is better for bleeding the system. Also how long should "a while" be, until there is a contionous stream.


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## adroga (Sep 16, 2005)

I guess the only thing you could do is have the heater set on high? I dont know if that will make a difference...


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## johnnyhammers (Oct 13, 2005)

Heater must be on full hot, engine must be warm, and "a while" shouldn't be more than a minute, maybe two before the majority of the air is out. once you get coolant flow interupted by occasional gurgles of air, the time frame is totally different, at that point you'll just have to keep bleeding and adding coolant untill you get none or almost no gurgles. Make sure your coolant is completely full. 

As for the electronic thing in the line, I'd say yes it is suspect. Maybe it's just a temp sensor, or maybe it's a cutoff/backflow prevention valve? That is a good question for the shop manual. And if you don't own a shop manual than you need to either get one if you're going to work on it yourself, or just pay someone else to work on it. I see too many folks trying to just figure it out on there own, so this is one of my common rants. I'm all about not paying for a mechanic.

Also try calling or visiting the dealership. I find that the guys at the parts counter are often willing to give advise, or at least a good schematic of the system that may be more helpful that the old Haynes/Chilton manual. If they try to send you to the service guys, just tell them you'd like to try to trouble shoot the problem before you make a service appointment. But they might also just be pricks at the dealership. You just never know.

Good luck
Johnny.


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## 89maximafrommom (Oct 16, 2005)

Loosened/Removed the bleeder bolt with the engine running and warm, heater on full. No coolant from bleeder. Radiator full and reservoir at max. I will see what I can get from the dealership.


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## CBPMIKE (Feb 2, 2005)

*Full cold valve*

I had a similar problem. You mentioned the "valve thing" on the fire wall between the the heater hoses. That was my problem. It's a vacuum valve used for cooler air performance - it blocks water from going through the heater core. Try moving the plunger on the valve by hand either in or out and see if the heat comes on - good luck!


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## adroga (Sep 16, 2005)

Keep us updated as to what happened at the dealer.

I am having a similar problem. 2 years ago I replaced my T-stat and bled the system, but broke the head off the bleeder bolt and wasnt able to bleed the system until today. The car takes forever to warm up, but when its warm the heat is nice and hot. The only problem is when I start driving on the highway, the engine over cools and the heat dies down. The temp guage actually goes almost all the way down to C.

Now I believed that my system needed to be bled. I extracted the bolt and some coolant came out.. the car was on an incline. Then I parked on a flat surface and the coolant didnt gush out unless I played with the throttle.

I am due to replace the timing belt, water pump and tstat(again) in the next few weeks, but I dont think it will be the tstat..

What is that plunger thing called near the firewall between the heater core hoses? What else could cause supercooling?


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