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Old 04-11-2000, 09:26 PM
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Default my heater is always blowing hot air!

It just started doing this, why? It runs all the time out of the defrosters...

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Old 04-12-2000, 08:58 PM
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Default Re: my heater is always blowing hot air!

I believe that the doors in the heat system in the dash are vac. controlled. Sometimes you have to put a mini (size of dime) diaphram into the vac lines going into the dash. This may not be your problem at all but one of my mechanics used to work for dodge and said that they had a recall on caravans I think and this was the solution. During acceleration the lack of vac causes the vac operated doors to open allowing air into the defroster. Like I said, this may not be your problem but good luck. SKEETER

89 XJ chevy 350, 700r4, 231c, 4.5 Rough Country
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Old 04-12-2000, 11:58 PM
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Default Re: my heater is always blowing hot air!

Another thing to check is the operation of the vacuum operated valve in the heater hose in the engine compartment. This valve is normally closed, meaning it needs vacuum to open. When the engine is running and the cabin control is not calling for heating, vacuum closes the valve, stopping flow thru the heater core. When the engine is shut down, the lack of vacuum allows the valve to open therby allowing coolant to flow bypassing the closed engine thermostat. This allows the pressures to equalize and prevents an air bound system. If the valve fails in the open position, you would get hot coolant through the core at all times. Good Luck!![img]/wwwthreads_images/icons/smile.gif[/img]

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Old 04-13-2000, 11:17 PM
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Default Re: my heater is always blowing hot air!

That was it, stuck valve!
Thanks!

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Old 04-13-2000, 11:31 PM
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Default Re: my heater is always blowing hot air!

[img]/wwwthreads_images/icons/smile.gif[/img]You're welcome!![img]/wwwthreads_images/icons/smile.gif[/img]

My post is somewhat inaccurate, however. Upon reading it again, I realize that the open heater hose valve doesn't bypass the engine thermostat. The valve will let the pressures equalize across the water pump, not the thermostat.[img]/wwwthreads_images/icons/crazy.gif[/img]

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