heater core valve vaccum issue

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Rick Byrne

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Mar 18, 2010
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Back in September I posted a problem I was having with my heater no working. After some investigation I am not getting any vaccum to the heater core valve but everything else that is vaccum works. Also when I open the valve manually both heater hoses get super hot but it will not blow hot air. I pulled the cover off and exposed the temp gauge and there are no vaccum lines to it. The vaccum line that comes from the heater core valve goes to no mans land behind the center of the dash. What can I do with out removing the dash? :banghead:
 
I'm not quite sure what your problem is because unless the ac is on there is no vacuum to the heater control valve. With no vacuum to the valve it should be in the full heat position. When the ac is turned on and vacuum is supplied to the valve the flow of hot coolant through the valve is cut off so the ac system does not have to overcome a hot heater core.



So can you explain a little better what your problem is. You said it will not blow hot air but does it blow any air at all? Do all of the blower speeds work? Do the vent positions change accordingly to where you put them? And last but certainly not least do you have automatic temperature control?
 
Similar question as l1tech: Do you have electronic HVAC setup or the analog? If electronic take a look at my writeup for replacing the Electronic Fan Controller in the Maintenance section of Projects. I had lost all control of modes/temp/fan speed in my 07 Limited. It was an easy fix once I zeroed in on what/where the faulty part was. You might want to check site sponsor Fast Parts Network's website for an HVAC diagram.
 
It blows air on all four speeds. The vent positions all work. Everything works like it should, except the temp control. It is an analog system. Also whether or not the ac is off or on, the heater core valve does not move.
 
Like I said earlier if there is no vacuum to the heater control valve it defaults to the fully open position so I don' think that is the source of your problem however if no vacuum gets to it when the ac is turned on that in itself is an issue.



I suspect that you may have an issue with the temperature blend door actuator. It is located just off to the right of the gas pedal and a little towards the rear of the vehicle. To access it remove the kick panel that is by your right foot and you should see the actuator, it will be a about a 3 inch square box with a plug in it. On that box you will see a white circular area with a square hole in it, this is the drive for the actual door. Change the temperature from full cold to hot or vice versa and see if the circle rotates, if it does this means that the actuator is working if it doesn't chances are that the actuator is bad however there could be another problem. If it doesn't turn you could also try giving it a little tap with the handle of a screwdriver, sometime they get a little stuck.



If the actuator moves and you still do not get any change in temperature the door inside may be broken.
 
It WAS the actuator! O'Reilly's had it for $50. Pulled the kick panel and the panel below the steering wheel. 3 (7mm) bolts and it was fixed. I appreciate the advice guys! :banana: :driving:
 
rickyb, thanks to l1tech you just saved $200+ and hassle of a shop visit. He gave it to you on a platter - after he got the full details of your problem. Pretty nice advice, wouldn't you say?
 
l1tech probably hit that on the head. I had to change the temperature blend door actuator on my 2001 and also on my 2007. So far my 2010 is ok but I sometimes the fan speed blows slower out of now where then goes back to normal.
 

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