DEFROSTER ONLY BLOWS COLD AIR

  • Tiny
  • Reggie101
  • 2002 Nissan Altima
  • 112,989 miles

Defroster only blows cold air. Only get warm air out of vents. Changed my thermostats and heat increased a little

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Monday, December 24th, 2012 AT 12:05 AM

6 Replies

  • Tiny
  • KHLow2008
  • Expert
  • 41,997 posts

Is your HVAC manual or automatic?

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Monday, December 24th, 2012 AT 12:58 PM
  • Tiny
  • Reggie101
  • Member

It is a manual

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Monday, December 24th, 2012 AT 2:02 PM
  • Tiny
  • KHLow2008
  • Expert
  • 41,997 posts

Refer to diagram

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Monday, December 24th, 2012 AT 3:17 PM
  • Tiny
  • Reggie101
  • Member

Lower radiator hose is cold. All other hose work properly

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Monday, December 24th, 2012 AT 3:48 PM
  • Tiny
  • KHLow2008
  • Expert
  • 41,997 posts

Lower radiator hose would be colder than upper hoses until the thermostat opens.

The hoses refered to are the heater core hoses, are both hot or one is colder than the other?

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Tuesday, December 25th, 2012 AT 2:07 AM
  • Tiny
  • mxvet21
  • Member

On these Altima's, the heater core is physically higher than the radiator. Air can and will get trapped in the heater core, leaving you no heat.

Ensure radiator is topped off with anti-freeze.
I disconnected BOTH water lines to the heater core.
Holding both lines vertical, I poured anti-freeze into one line until it flowed out the other.
As Quickly as I could, I plugged end of hose with thumb, and reattached to engine.
Ditto with the other line.

If you search around, this is not uncommon.
Typically it is referred to as "burping" the engine.
Others have parked on a hill, engine high, pulled cap (WITH ENGHINE COOL), fired it off and let it run. Hopefully air in heater core can work its way back to radiator.

I DID try this, but did the hose thing to make it quick and easy.
I have never had problems since.

WATCH YOUR RESERVOIR - These Altimas (Nissans) seem to develope leaky head gaskets. I had a slow leak, and just kept on topping it off reservoir.
I finally bit the bullet and pulled the head, had an entire valve job done, and reinstalled using new gaskets. Job sucked, and it took me 6 days, trying to do all my other required tasks as well. I WOULD do it again though, now that I know the ins and outs of my Altima.

NOTE: Altimas have TWO thermostats on engine. One is for heater core, and the other for the engine block discharge to radiator >> this one is the one facing the radiator, midway down your engine.

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Friday, February 1st, 2013 AT 3:08 AM

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