Loss of heat when you turn to defrost position

Tiny
LUTHARTHEGREAT
  • MEMBER
  • TOYOTA COROLLA
Hello,
I have a 1999 Toyota Corolla 4 cylinder 3 speed auto transmission with around 112,000 miles.
This thing will run you out in zero weather when you use dash or floor or combination. As soon as you turn it to defrost, it kicks the AC on ( I know this is normal in order to remove moisture from the cab) the thing will start blowing cold air out vents. Turn it back to dash or floor and it will take 3 min to become hot again. I replaced the thermostat and flushed the cooling system to ensure it is good. I ran the engine to get it to cycle the engine fan and it cycles fine and coolant apears to be circulating fine. I touched both inlet and outlet to heater core and they are hot to the point you cant hold them very long.
Im not sure what to check next. Is there a ambient temp sensor that senses outside air in order to control the AC on heat? Anyone have any ideas?
Thanks in advance.
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Saturday, October 20th, 2007 AT 1:58 PM

9 Replies

Tiny
MERLIN2021
  • EXPERT
You need to get under the dash and check the operation of the blend door, it may be binding. This balances the hot and cold air entering the car.
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Saturday, October 20th, 2007 AT 2:26 PM
Tiny
LUTHARTHEGREAT
  • MEMBER
Thanks for the reply, I have the complete dash out and everything appears to be working and opening and closing as it is supposed to. Not sure what to look for next.
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Saturday, October 20th, 2007 AT 3:54 PM
Tiny
MERLIN2021
  • EXPERT
Look far a leaking servo, tht's the vacuum motor. Does any of them reopen after they have moved? It sounded like you said it took 2-3 minutes, then the cold set in? Also when it turns cold check the water inlet to see if it has cooled. If there is a valve in the waterline it may be closing the water flow off!
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Saturday, October 20th, 2007 AT 4:14 PM
Tiny
MERLIN2021
  • EXPERT
Here are some test proceedures to follow!


http://www.2carpros.com/forum/automotive_pictures/62217_Heat1_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_Heate1r_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_Heat2_1.jpg



http://www.2carpros.com/forum/automotive_pictures/62217_Heater_1.jpg

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-1
Saturday, October 20th, 2007 AT 4:23 PM
Tiny
LUTHARTHEGREAT
  • MEMBER
Thanks for your quick response, I will check the things you have suggested and go from there.
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Saturday, October 20th, 2007 AT 5:26 PM
Tiny
LUTHARTHEGREAT
  • MEMBER
I have to borrow a volt meater but I don't see any inline valves or none of the servos seem to be moving once they are in position.
Something new today.
Well my son informed me this morning that his car is not getting very warm going down the road. So it appears that as you go down the road it is cooling off and he stated the heater gauge remained in the same location. So now after I have flushed and replaced the thermostat and coolant it has gotten worse even off of defrost.
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Tuesday, October 23rd, 2007 AT 9:16 AM
Tiny
MERLIN2021
  • EXPERT
See if you can disconnect the heater hoses at the core inlet, then make an adapter for your garden hose with the flush kit, hook it up to the core and flush it real good, both ways! Heater cores are not built like radiators, they are a honeycomb type flow.
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Tuesday, October 23rd, 2007 AT 2:00 PM
Tiny
LUTHARTHEGREAT
  • MEMBER
Looks like I found my problem. Now I cant decide if I should change the radiator in order to keep the trash out of the new core? Holy smokes $200.00 and no one keeps it in stock.
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Saturday, October 27th, 2007 AT 10:56 PM
Tiny
MERLIN2021
  • EXPERT
You can take the radiator to s radiator shop and have them boil it clean. Won't cost as much as a new one.
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Sunday, October 28th, 2007 AT 7:51 AM

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