86jeep Posted December 2, 2011 Posted December 2, 2011 I bought my mj and the heat don't work it blow cold air out of the ducts please help. i went and bought a new thermostat. when i took the old one out it was open but i just drove the truck all day. it closed when i took it out. i went ahead and put my new one in. what could it be please help i put the old one on the stove it open up and close when i ran cold water on it so it was good please help
Akula69 Posted December 2, 2011 Posted December 2, 2011 If you have a sufficently warmed up engine and the blower operates you are probably looking at the heater control valve. This valve is vacuum operated and located up by the firewall on the passenger side. It is in the group of lines that go to and from the overflow tank. You may need to either check the vacuum supply at the valve or the vacuum line that comes out thru the firewall by the heater core connections. The other possibility could be that the valve is broken or debris has clogged it - in which case you might need to replace it. Some folks have cut the valve out and connected the lines straight thru, allowing the coolant to flow through the heater core full time. In any case, do not mess with it when hot. The valve body is plastic and will break, spewing hot coolant all over the place. Good luck!
cruiser54 Posted December 3, 2011 Posted December 3, 2011 Agreed^^. They stick shut from lack of use during the summer. You can eliminate it if you wish with no repercussions.
86jeep Posted December 3, 2011 Author Posted December 3, 2011 which side do i eliminate both side has something there like 5 hoses my is a 86 2.5 auto
Akula69 Posted December 3, 2011 Posted December 3, 2011 which side do i eliminate both side has something there like 5 hoses my is a 86 2.5 auto Take a clear picture of that area and post it here. We will show you what you can safely remove. Best I can do at the moment unitl I can search for the pics of the valve on the forum.
flint54 Posted December 3, 2011 Posted December 3, 2011 http://comancheclub.com/forums/viewtopic.php?t=11077
64 Cheyenne Posted December 3, 2011 Posted December 3, 2011 Look at the underside of the bell shaped actuator, there is an "arm" that moves to open the valve. Try to turn heat on see if this valve moves. On my old 86 2.5 I used to just push it with a screwdriver to get heat, wasn't worth the time to tear apart. Worse case scenario, could be a plugged heater core.
jeepcoma Posted December 3, 2011 Posted December 3, 2011 What's the purpose of this system anyway? Faster warmups when the heater is off? If the heater core leaks the flow can be stopped? Seems kinda like the CAD... interesting in concept but no real point :hmm:
86jeep Posted December 3, 2011 Author Posted December 3, 2011 there no arm to move why can't i just take that hose that goes to that bell shape thing ad just bypass it
cruiser54 Posted December 3, 2011 Posted December 3, 2011 There is an arm. You're just not seeing it. It's on the firewall side of the valve.
86jeep Posted December 3, 2011 Author Posted December 3, 2011 i see the arm after i took it off it was froze so i just bypass it i will just block off the little vacom hose
Akula69 Posted December 3, 2011 Posted December 3, 2011 Your welcome...but more importantly - do you have heat now?
64 Cheyenne Posted December 4, 2011 Posted December 4, 2011 there no arm to move why can't i just take that hose that goes to that bell shape thing ad just bypass it Take an inspection mirror and look on the other side. And you could just remove the valve, but what a PIA trying to get the heater working when the weather gets cold, go figure... :dunno: Me, unless I had a garage, I'd push the actuating arm, see if it works then leave it till spring.
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