Heater will only keep blowing warm with high RPMs

Tiny
OLDSCHOOLMUSCLE
  • MEMBER
  • 1992 CHEVROLET CAMARO
  • 265,000 MILES
I am having issues with my heater blowing hot. It will work as long as I maintain at least 1,500 RPMs and a decent speed but if it drops then it starts blowing cold air and the engine starts to overheat. I have a feeling it has something to do with the vacuum that controls the heater but not sure if it would be just a line or if it would be the heater control box itself.
Thursday, January 12th, 2012 AT 10:47 PM

3 Replies

Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
With the engine idling and at operating temp, grasp the 2 hoses going through the bulkhead for the heater core. They should be HOT. Check thermostat, make sure it's opening properly. Make sure you can see coolant flowing in the radiator.
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Friday, January 13th, 2012 AT 12:29 AM
Tiny
OLDSCHOOLMUSCLE
  • MEMBER
  • 2 POSTS
All of that is working properly. It just doesnt want to stay on heat. I just dont know if it would be the selection box or a vacuum line to the box
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Saturday, January 14th, 2012 AT 1:21 AM
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Use brake cleaning fluid or carb cleaner to check the vacuum lines for leaks. Make sure the actuators are moving the blend doors properly.
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Sunday, January 15th, 2012 AT 5:18 AM

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