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No cabin temperature...

1475 Views 17 Replies 4 Participants Last post by  amc49
So after a full hose check, rad flush and new coolant, I can get at best 'warm air' into the passenger cabin - which with -5 already and -40's around the corner is not good.

The engine is producing good heat, everything seems to be flowing as it should but none of that lovely heat is getting into the cabin.

As an aside, last winter we thought the fan speed resistor had quit as only the high speed setting would work, so we bought another one, installed it, switched it on - all 4 speed settings worked fine for the first 3 days after which - same as before only the high speed working. If the one fan speed is working - what is causing the others not to work?
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There is also an a/c bypass door that if open will do same thing, it has to be the opposite or closed to work. So, two doors there. That a/c one is exposed when the glovebox is opened then fully dropped to dump its' contents on the floor. Look at blower and the small slits in box there, the slits should have the door behind them blocking the slits from passing air, if the slits open up into deeper area the door is still open and needs shutting. The shaft to that one is known for stripping to not work, you can make a hook out of coat hanger to reach inside slot to pull door back down closed.
The blower switch as well can fail to give only high speed, happened to mine.
These are full flow to the heater core all year long (again for sure on the earlies, I have '00 and '02) and why generally most of the time the core does not plug up, that is much more likely on old school cars with water control vales that cut off flow to the heater core. That is what allows them to plug when the sediments settle to stagnate and clump. Clogged core on these is pretty rare.
FocusKnot I owe you and others here an apology, I'm an idiot. Your surmising was correct on that a/c bypass (recirc) door not affecting heat output.

Something about what I posted (I've wiped it now to be gone) kept gnawing at the back of my mind and I went out to the car and directly checked that door action for heating effect. I was DEAD WRONG THERE. The door open or closed effects the air output only slightly and the temperature not at all. I apologize to Vision1961 if he actually worked on things under my assumptions, which apparently were that ONLY.

So where did that idea come from? Part of the digging in the cobwebs that are my brain at 60+ years old now. I know for sure I fixed an AMC Concord once closing that door when it wouldn't heat and instant heat doing so. I locked that into my head good back then and it has probably polluted more recent thinking. Like so many other things do when you assign them as firm rules only to have them shattered to pieces with the next car's design changes. Digging in the rubble there was what got me to thinking I thought I knew when I really didn't and only one cure for that. Test the idea NOW. I failed.

Again I apologize if I misled anyone incorrectly.

Looked at heater core supply path as well. When stat is open or closed the core is supplied pressure by part of the bypassing water from the small hose on back of stat housing. The suction side of it is the hose running from core all the way up to the plastic manifold at top of radiator. The other water flow either uses the small hose on front of housing to bypass radiator when stat closed or goes through stat when it is open to go to radiator. The disc on back of stat makes a clean switch between the two loops there when it closes at stat fully open. The bypass loop heats the water up faster until car is warm. The heater core itself has full flow at all times. This is on zetec engine.
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I'm speechless..........................and that's pretty damn rare. Maybe another condition has to be in place at same time. I thought it changed it years ago but when I did it like two days ago nothing, no change at all. I swear I'm not crazy (DON'T START!!!) LOL
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