MY HEATER WILL ONLY BLOW HOT AIR AT THE FRONT ...

  • Tiny
  • henryr79
  • 2007 Saturn Relay
  • 93,000 miles

My heater will only blow hot air at the front while driving and the rear never gets hot, but once I stop even for a red light the front turns cold. What could cause this?

Sunday, October 28th, 2012 AT 8:06 PM

17 Answers

  • Tiny
  • saturntech9
  • Expert
  • 28,246 posts

Sounds like you have a restricted heater core possibly.

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Sunday, October 28th, 2012 AT 9:18 PM
  • Tiny
  • henryr79
  • Member

I am guessing that this vehicle has two heater cores. Am I correct with this guess? I am assuming after readingyour answer that both are restricted, with the back one being totally blocked. Is this a correct thought, since the back seat never gets heat, and the front is hot only while driving and gets cold rather quickly when you stop.

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Monday, October 29th, 2012 AT 1:19 AM
  • Tiny
  • saturntech9
  • Expert
  • 28,246 posts

Yes there is a front and rear heater core after the engine warms up heres what I want you to do. Set the front heater to the hostest temp setting with the lowest fan speed. Then see if both heater hoses to the front heater core are getting really hot?Then do the same with the rear heat and see if both heater hoses to the rear heater core are getting really hot?Let me know what you find.

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Tuesday, October 30th, 2012 AT 4:57 AM
  • Tiny
  • henryr79
  • Member

Both hoses for the front get really hot if you rev the motor up, if you leave it at idle only one gets hot. At the rear both get hot only if you rev the motor, otherwise both hoses at the rear are cold.

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Friday, November 2nd, 2012 AT 11:00 PM
  • Tiny
  • saturntech9
  • Expert
  • 28,246 posts

I first check the front heater core for blockage start there. Have you ever used stop leak in the cooling system since you have owned it?

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Saturday, November 3rd, 2012 AT 12:40 AM
  • Tiny
  • henryr79
  • Member

I have never used stop leak since I bought the van with 43000 miles, of course I don't know the history for the first 43000 miles.

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Saturday, November 3rd, 2012 AT 1:45 AM
  • Tiny
  • saturntech9
  • Expert
  • 28,246 posts

Have you checked to see if the front heater core is restricted or clogged?

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Monday, November 5th, 2012 AT 2:58 AM
  • Tiny
  • henryr79
  • Member

Not yet, but should I just pull it and try to shoot water through it in both directions from a water hose nozzle? It will be at least next weekend before I can try anything.

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Monday, November 5th, 2012 AT 3:09 AM
  • Tiny
  • saturntech9
  • Expert
  • 28,246 posts

You can do that but I wouldn't remove the heater core to check it I use compressed air to check them.

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Monday, November 5th, 2012 AT 5:16 AM
  • Tiny
  • henryr79
  • Member

Iuntil you rev the motor?I took the hoses loose from the rear and flushed water from both directions. I saw nothing but clean antifreeze come from the heater core, then I took the lines loose up front before the wyes and flushed from there, still nothing but clean antifreeze. I then put everything back together, started the van, got no heat after warming the engine until I reved the motor. The lines at the back of the van never got hot until the motor was reved up for a while, then they got hot and I could feel heat, but after returning to idle everything got cold again. Do these vans have a problem with the water pump possibly not pushing the water through the heater cores

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Friday, November 23rd, 2012 AT 11:22 PM

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