knoslf
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Hey xeqshnr I know this is old but did your heat work before you connected that vacuum line? And do you know what the line on top of the one you connected(to the piece on the firewall) goes to?
Vacuum line help
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Hey xeqshnr I know this is old but did your heat work before you connected that vacuum line? And do you know what the line on top of the one you connected(to the piece on the firewall) goes to?
My heat worked months before. I had just got with replacing the intake gaskets and it was the middle of summer so Idk if the heat worked before I reconnected that line. And I really dont know for sure what the other one is for, sorry
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Harry Hood
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Just replaces this HVAC valve on my Tahoe and with the line connected my heat does not work.
With it disconnected it works perfect.
Anybody an idea of why this is?
With it disconnected it works perfect.
Anybody an idea of why this is?
east302
Full Access Member
The vacuum line on the heater control valve connects to a solenoid on the firewall. From what I gather, when the solenoid is energized vacuum is applied to close the control valve, closing off coolant flow to the heater core. I've read that this is supposed to happen when the a/c is on, but I'm not seeing that on the wiring diagram. It looks like voltage is applied when the temperature dial is set to the cold detent (max) setting.
Maybe someone else knows, but I'd look to see if you're getting 12V to that solenoid with the temp dial not set at the cold/max detent. If you are always getting voltage and energizing the solenoid, then the problem may be in the hvac control panel.
Also, with the temp dial not set in cold detent, unplug the solenoid (with vacuum line connected) and see if you get heat. That, to me, would indicate that the solenoid is bad.
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Maybe someone else knows, but I'd look to see if you're getting 12V to that solenoid with the temp dial not set at the cold/max detent. If you are always getting voltage and energizing the solenoid, then the problem may be in the hvac control panel.
Also, with the temp dial not set in cold detent, unplug the solenoid (with vacuum line connected) and see if you get heat. That, to me, would indicate that the solenoid is bad.
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