QuestionQUESTION: My 1999 Yukon (with 5.7L engine) heater valve solenoid allows vacuum to pass through at all times....always open...even with electric connector unplugged. Thus, the heater valve modulator "thingy" is always pulled tight which is apparently the mode for coolant to bypass the heater core. I have no voltage at the female end connector on the wire harness to the solenoid when the AC controls are on heat - or any other time that I can tell. I assume that something is supposed to send a signal to the solenoid closing the valve and restricting the vacuum to the heater valve when heat is called for. That signal does not seem to be making it to the solenoid at any time.
1.) Should I be able to read any voltage at the female connector, and if so what voltage and at what dial selection on the AC/Heater controls?
2.) Where does the signal come from? I have three knobs on the dash: Fan. Blue/red. Vent positions.
3.) If I plug the vacuum port from the solenoid going to the heater valve, and allow the heater valve to pass coolant to the heater core at all times, will that affect the AC's ability to cool? All mixer/blender doors appear to work fine.
Thanks in advance. Your help is greatly appreciated, as I've already learned a TON from reading your past posts.
ANSWER: Hi Ben
Please follow post back, if possible. I can find NO information AT ALL about the vacuum solonoid on the heater control valve.
Please follow post back
Pawl
---------- FOLLOW-UP ----------
QUESTION: Thanks for looking, Pawl. Maybe I'm calling the vacuum solenoid the wrong thing. There's a vacuuum line that goes through what I'm calling a vacuum solenoid on the Passenger-engine side -firewall, and it terminates at the heater valve. When the vaccuum is on(engine runing) it pulls the modulator on the heater valve tight, closing the flow of coolant to the heater core. I've got the vacuum disconnected now for winter (plugged so the engine doesn't know the difference), which allows the heater valve to remain open and pass coolant through the core. I would like to just leave the vacuum line plugged, and the heater valve open, but don't know if that will make it harder for the A/C to cool in the summer time. The temp switch (blue/red switch in middle)seems to control the heat an cool air OK, now. What do you think?
AnswerHi Ben again...
OK I understand your question better now...( I thought you where having a prob with the valve opening)
You are going to be OK in this as the temperature control doors inside the vehicle will open/close according to the input of the switch. So if you have it on full cold, one door will close off the heater and open the A/C Evaporator. If you "blend" the temp, eg...say 70*F, the door will open half way and allow cold A/C air to blend with warm heater air.
This is how most work anyway without the Heater Water Bypass Valve.(eg trucks and other SUV's with same HVAC system)
I have also seen others even eliminate the valve totally, due to cost of replacement part when it leaked.
You should never see a difference, UNLESS there is a problem with the door/duct system.
I REALLY hope this helps.
If you like, if you follow post back, click the private box, I'll send you along my email addy, so you can get in touch with me directly, if and when needed.
I still am looking for this......and if I find it out, I'll SURELY let you know.
Again, I hope this helps
PAwl
