I have a 95 Nissan Maxima. It has a manual climate control. Out of the blue my heat stopped working. Keep in mind the Heater core was replaced about a month ago. I was driving and it got too hot so I switched the temperature to cold all the way home. I got home car sat for about 15-20 min got back in my car was cold so I decided to turn the heat on. Now no heat! What happen? Ok so fine maybe my climate control unit is messed up I thought. So I figure ok maybe I'll just get a new one. The day before I get the new one all of a sudden my heat comes back on out of the blue. I'm like What the? Ok I was like I don't need a new one fine. Keep in mind I was able to put the **** in the middle to warm(I never tried to bring it to cold because I was afraid it would happen again.) STUPID ME! I was cleaning the dash what do I do? Freaking swipe the damn thing to cold by accident. Didnt think anything of it at the time because I didnt realize I did that. Get back in my car it's cold about to turn the heat on. OH **** it's on cold. I pray please work sure enough it doesn't turn on now I've been stuck with cold ever since and it sucks. Now met up someone on Nycsmaximas.org to buy a new climate control. Install it heat still don't work. On my previous climate control peice all i was able to do was turn the top vents on and the defrost would come on but wouldn't switch to the window vents and just stay on the top vents whatever button I pushed. So I get the new one install it wow cool now my floor air, window air, all of it works awesome, right! WRONG! Start seeing the thing start to smoke now you get this nasty burn smell. NOW it's freaking stuck on floor air and window air. Well obvisously I fried it and now it's stuck. Looked at all the wires and can't figure what happened. SO NOW, my dilemma is what's wrong with the heat and why is it burning out? Sorry for the long @$$ story. But figure into as many details as I can.

 

Sounds like your blending door isn't switching positions.

 

what is a blending door?

 

It a door that separates the air coming from the evaporator and heater core. It's usually controlled by a motor when you want to change the temperature in the cabin. When you want cold air from the AC, it blocks the heater core passage in your ventilation sysytem. When you want heat or warm air, it blocks off the AC evap section. If you want something in between, it allows flow from both areas at the same time.

 

How can I fix this? Is this the black box? Is it a electrical matter or a switch?

 

I have never fooled around with that part of a Maxima but most likely there is an electrical connector in the back of your AC controls that actuate the various motors that control the vents and doors. You should consult a service manual to help you understand the wiring. It could be several things wrong and it's better to go step by step in troubleshooting the system.

 

If it is a manual system, it could be as simple as a cable came off the water control valve! Earl

 

Do you know where that would be located?

I checked all wires behind the climate control they all seem to be intact and nothing disconnected. I really appreciate everyones help. Tomorrow I will be taking it out and analyzing it more. I can access the air mixer box under the dash if i take off the glove compartment right. I just hope i never have to take that whole dash off again like i did for the heater core.

 

what do i have to do to change it?