Ok, guys I am having a problem with my heater not blowing hot. It will blow warm for about 5-10 seconds. After that it starts getting cool, and blowing cool air. I have purged the coolant system many times. I just bypassed the heater control valve to see if that was the culprit, no luck. Both heater hoses are very very hot. I tried back flushing the heater core also. I bought this car a year and a half ago, and have never gotten the heater to blow hot. I am suspecting that it may have something to due with the vents or a vent door. Any ideas?????? I really got to get some heat for this car before winter comes. Please help!!!!!

 

Is your thermostat working properly? I had that problem on a 92 GXE I had once.

 

yeah, new thermastat.

 

Thermostat and make sure have no air pockets in the cooling system.

 

All that is done. The heater will blow warm for 5-10 seconds, then cool air. What gives????

 

I just re read your first post. My buddy had a civic just last year. He bought it and it wouldn't get hot. After trial and error no luck. Got to looking under the dash and all the vents where broke and cracked. After he fixed it blew hot. But don't make sense why yours does for few seconds the stops. What happens if after stops blowing hot shutting off heater then turn it back on or shut off car and reset it?

 

I remember my father in law (RIP) had the same problem - he spent a small fortune getting it fixed, only to find the control lever to let in outside air was flipped on......

 

a good flush of the cooling system could work as well with new coolant/water mixture. dont know if you just replaced the thermostat and topped off the fluid or what, but thats an option...and double check to make sure you dont have any air in your cooling system

 

I know it sounds stupid but one time i knocked the small over flow tube off the top of my rad and that caused me to not have heat. it essentially made the rad op[en and not retain heat.

 

My max did the same thing when I first bought it. It would be really cold outside and I would go to start her up, and would take nearly 30minutes for the gauge to move up on the temp hand. If I move I used to hear water moving around inside the car. I would have heat until the car moved( like stopped at a light or something I would have heat temporareily) then once I moved the car the needle would move from the middle, and back to cold, and it would do this everytime. So something said to me that the thermostat might be stuck open, So I bought one and installed it, and problem solved. I had heat for a little while until my core started leaking.

 

Ok, guys here's an update. I talked to a mechanic today and he said that it sounded like that there might be a vent door, or a cold door......some kind of door in the venting system either letting cold air in or letting hot air out. So, on the way home I pushed the defrost button on the manual climate control with the fan off and cold air is blowing through the defrost vents!!!!! Does this mean that a door or vent is letting cold air in??? Sorry, but I don't have much knowledge about the venting system of an automobile. I am guessing that I will have to start tearing the dash apart. Could someone please look at the factory manual and give me some insight on what I should be looking for???? Thanks!!!!

BTW- Thermostat, water pump, head gaskets and air purged from the cooling system was performed. Thanks!!!

 

Do you have manual or auto air control?

If you have a manual there are two buttons to know about.



What I highlighted #1 in the pic is the air recirculation. When it is off, air will come in through the vents while you are driving (think of it as wind blowing in when you have the window open, but from a door somewhere in the vent system). I'm hoping that is what's going on from your last reply. I believe the defrost button will turn off recirculation by default too.

Nissan calls #2 the fresh air inlet switch. I call it the heater core bypass switch because what it does is that when the lever is up, a door that is located right after the AC evaporator will open up and allow some air to enter the open duct, which bypasses the heater core, and exit through the vents. Make sure the switch is down if you want hot air.

If you have that switch down and you're still getting cold air, I would suggest looking at the cables that control the fresh air vent and temperature control doors. Another thing to look at is the heater control valve that is located right on the firewall. Make sure the vacuum hoses are attached and not craked. One of them should go into the intake manifold.

 

Now you can look at it yourself....http://www.nicoclub.com/FSM/maxima/1994/

 

I have the heater control valve bypassed, #1 is pushed in, and #2 is all the way down. Is air supposed to come through the defrost vents when the defrost button is pushed????

 

yes, it should.

now, you "bypassed the control valve", you mean the vacuum valve, right? (just to be clear).
when does it blow the warm air?
does the temp slider move freely, or offer some (slight) resistance?
your fan works, right?
who bled your coolant system, and how?

 

1. I bypassed the heater control valve. (water ****) - both heater hoses get extremely hot.
2. It never blows hot. Even when it reaches normal operating temp (halfway on the temp gauge) it will blow ice cold up until about 15 minutes of highway or city driving to get faintly warm. It seems like when I turn the fan on it will blow warm for about 10 -15 seconds, like it wants to blow warm, but the warm air goes away and starts getting cooler, not cold, but cooler. After I cut the fan on, I have to wait about 10 minutes before the air will get warm again and I can turn the fan on. If i leave the fan running the air never gets warm. The fan has to be cut off for the air to get warm again.
3. When I slide the temp slider toward the cold side i hear what sounds like a door closing. When I slide to the warm side, i don't hear anything.
4. The fan works (blower motor)
5. I bled the cooling system. I jacked up the front end, got the air bubbles out, (30 minutes or more), I opened the bleeder valve on the intake , topped it off with coolant, lowered the car. Whew, I hope this helps. Thanks!!!!

 

Have you taken the climate control assembly out of dash yet? I would be checking the clips/cables, air condition switch, wiring. I have the electronic push button system in my Max but the lever controlled system can be adjusted when you run into problems. It sounds like you have checked much of the engine bay part of this system and that's why I ask about the simple stuff like climate control panel, cables and ****.

 

I actually changed out the the climate control a few months ago because the number 4 fan speed stopped working on the previous one. I am going to poke around the dash this afternoon.

 

Ok, I flushed the heater core out yesterday with some vinegar and ran the water hose for about 30 minutes. I have heat now. Yay!!!!!!!

 

Good to hear.

 

You have heat and I dont! Im mad at that lol! Good to hear that man. I will be tearing down my dash today and installing a heater core, its getting to cold down here at night.

 

Ironically is was in the twenties the other morning and i also found myself without heat.

40 miles one way to work on the highway, I'll be needing heat.

The temp gauge never moved up at all.

 

I like the thread title
"another heater won't blow cold thread"

My refrigerator won't cook my food.

But I'm glad the problem is solved. In case it happens to me.