Manual A/C Heater Problem

[Dan Szwarc]

66s require a normally closed heater valve.
I though I had pics of heater hose routing in my sig.
I think the side port goes to the junction block (intake) and the bottom port goes to the heater core.

[TonyC]

Yes, and that is how the hoses are routed. For a while I was not sure if that was right, but more intense studying of the shop manual's pictures and assistance from a few other Forum vets confirmed this to be correct.

Now, routing of the vacuum lines was not correct, and I have since fixed that. But that made no difference; in fact, even when it was wrong the heat used to work properly until now (except for draining vacuum from the cruise control if I tried running both those systems at once). The problem has to be in the controls, specifically the control panel.

---Tony

[George W]

If you use foam then I'm pretty sure it would need to be open cell, not closed cell. The cloth you mentioned would likely work fine as would a thin piece of felt. Maybe you could use some of those felt, stick on anti scratch pads for furniture legs that you see sold in hardware stores. Just cut some of the adhesive out from the center with an Xacto knife and stick them on.

Regarding the "water valve" electrical contacts. This seems like an odd description since the water valve is vacuum, not electrically operated. Could there be an on/off vacuum solenoid in series with the vacuum line feeding the water valve ?
Could these contacts have some effect on the operation of the a/c compressor clutch ?

[TonyC]

Yes, George, it does sound odd, doesn't it? It's even more odd that the shop manual shows that switch to be exclusive to the manual-A/C system, not shown or even referenced in the ATC option or the standard non-A/C system. But here is what I've figured: The solenoids that distribute vacuum to the entire system are electrically-operated. That switch is tied in somehow to the solenoid in the control box that operates the heat, and when the contacts are closed, that solenoid is energized, channeling vacuum to the blend door and coolant valve, permitting heat flow. When the contacts are open, that solenoid is de-energized, cutting off vacuum supply to those components to kill off heat flow. That switch is supposed to be open at the coldest setting and closed at the warmer settings. My switch is acting backwards. One would think that it's just installed backwards, causing the stop pin to operate it the wrong way...but I cannot see any other way that switch goes on, it looks like it can only go on one way. My assumption is that the switch, specifically its spring-loaded operation, has gone defective, meaning I'd need a replacement. I'm searching all over for somebody, anybody, who happens to have a manual-A/C control panel of my year to offer.

But I still have problems. I placed new covers over the solenoid holes, using flex bandage material the hospital conveniently gave me after they needled me up in my last visit; it's pretty filter-like, but it doesn't really clog up air flow. Since I did that and did a road test, the heat is gone again, completely. IF I ever do end up curing this problem, chances are I may not even know how to explain it here. This whole thing is getting really frustrating; I just do not need this happening to me, having to suffer heat failures in the dead of a Kansas winter, no matter how relatively mild it's been! I'm seriously thinking about resorting to drastic measures, like cutting the hose that feeds the blend door and heater valve, splicing it directly to a constant vacuum supply at the engine, and running that way to at least get through the winter.

---Tony

Follow-up, 5 February: Never mind that; I did that and it made no difference. So, today, I just put all the vacuum lines I rerouted back in their original places and went in at another angle: I disconnected that "blend door and water valve switch" and inserted a jumper wire to its connection. I haven't bothered to test it, aside from making sure it did not cause a short-circuit, because with all the frustration this problem has caused me I don't really want to know today that that won't make any difference. I just have to wait until I'm able to throw more replacement parts at it until I finally fix it somehow...or ride out this winter so I don't have to think about it anymore.

[George W]

Is it possible that the blend door is stuck in a position that is preventing heat from escaping from the heater core ? Once the engine is warmed up do the heater core input and output side hoses feel equally hot indicating that you have water flow through the heater core ?

[TonyC]

No, George, that isn't the problem. The blend door and heater valve both operate as they should...except for one thing: Vacuum supply. The controls don't route vacuum to those two components at all, unless I bypass the regulator and hook the two vacuum hoses at the control panel directly into one another. When I do, the heater works...but if I travel above 60 mph, the heat is then cut off, coming back on when I drop below that speed. BUT, vacuum supply to all other systems is just fine even at those higher speeds; the cruise control holds steadily, the washer circuit moves the wipers with no problem. If it were an engine issue, all those other systems would also be affected, and they aren't.

It has to be a problem in the controls. I'm trying to find a replacement control panel at this point.

---Tony

[TonyC]

Although a bit premature, I'm bumping my thread to give updates to this epic mystery. My last post was on the day that the engine went into its coma, so naturally this went to the back of the line of priorities; now with the engine revived, it's back as the top priority. The problem as of today is still not solved, but I'm letting everyone know what I have done about this over the past three months.

Quick recap of the symptoms: Heated air blows normally when dialed in, but only at low speeds around town. On the highway, once the car gets up to 50 or 60 mph (a few times a little higher, like 65, but usually by the lower speeds), and without making any adjustments to the controls, the heated air turns cold; I mean completely cold, as though the vacuum to the heater valve and blend door has been completely cut off. A few times the air would heat up again when I dropped back to slow city speeds; but more often than not, the air would not turn hot again unless I turned off the system and turned it back on after several minutes of city driving. A couple nights ago, when this happened again, I left the system on until I got home, popped the hood, and tried to examine the operation of the blend door, just to confirm that the vacuum supply was being cut off from it and the heater valve...but before I could get into position to observe, the vacuum supply returned and opened the blend door, bringing hot air back into the car. Quite a mystery, eh...? Enough to make Sherlock Holmes OD on Scooby-Snacks.

Previous diagnoses: I had made a little noise over the past several months in the "Wanted" category for parts, specifically a complete control panel and a flap servo. I managed to acquire all these parts (thank you again, Fraser, John, and John!) and install them. Although they did provide their own benefits (particularly the control panels—one from John Brewer, the other from John Lyman—between them I now have a much brighter display at night, and I learned how that sprung-contact heater switch is supposed to work), they did not cure the problem. I then inspected the entire plumbing, even replacing all the engine-bay hosing with new hosing for good measure. I tested each and every vacuum component associated with the system: Reservoir (both chambers, in fact), main-supply check valve, blend-door servo, heater valve, A/C-Heat flap servo (which needed replacement along with its associated hose, and the replacements are in ideal working condition), Heat-Defrost flap servo, and the vacuum regulator on the control shaft. Everything is in proper working order...yet the problem still persists.

My latest guessing venture takes me back to the control box, which I also had replaced with no discernable difference in results. On one of the Facebook groups, one member posted about having problems with his own car's manual-A/C system, although his problem was different from mine: His problem was that all the air would blow through the A/C ducts only, no matter what setting he chose. Actually, last month in the course of still trying to find that elusive gremlin in my system, I ended up with exactly that same problem; swapping control boxes cured it. This member also confirmed proper condition for everything around the system, deducing that the problem was with at least one solenoid in the control box, and chose to try something I never had the courage to do myself: Disassemble the solenoids inside the box. His latest posting indicated that his attempt to rewind one of the solenoids with new copper stranding failed, so he bought an aftermarket A/C solenoid to try and serve the purpose of that one. No further update on his progress on that...but, based on his postings, I had a hunch that I followed on my spare box. Being that a solenoid is actually a relatively-simple electric component, I focused my attention on them, which I had not done previously. I did not dare try to remove them from the box or fully disassemble them, but I did check on one detail which triggered concern. I removed the removable part of one solenoid's shell, and I saw that each solenoid is grounded to its shell with a metal tab coming out of the solenoid and aligned against a similar tab on the shell; they are coupled by a small rivet and then glazed over with solder. I noticed that the solder had broken loose on the solenoids in my spare box; that triggered my concern. Broken soldering can compromise the grounding of the solenoid, even if the rivet is still in place; I was able to move the solenoid fairly easily back and forth in place, which led me to believe that it could be a grounding problem that is the cause of all this. Today I removed the box that was in the car, and I confirmed that the solenoids in it were in the same condition as the ones in the spare: The very meager soldering at the ground tabs had in fact worn or broken loose. I applied a liberal amount of new solder to each solenoid, to ensure that they are 100% grounded, and reinstalled the box. Today the weather was really too warm to test the temperature adjustment (but which did help motivate me to get into the car and perform the surgery), so I cannot report yet whether this avenue I took will have any impact. The different ducting modes still work properly with the pushbuttons, but I did not try adjusting the temperature. I will try that probably tomorrow. that I see a difference. I'm not going to make any presumptions at this point, though; after over a year of having this problem and ruling out every other possible cause to no avail, I've learned not to be all that optimistic. But this does seem to make some degree of sense to me, that poor grounding can compromise a solenoid's normal operation.

Anyway, that's the latest on this mystery, just in case anyone may have been curious.

---Tony

[rick]

Tony, we already knew you were a gamer from past experience as we witnessed your dogged determination with regard to Frankenstein's engine rebuild. I would have given up. So I will not be one bit surprised if you pull off a solution for this heater problem. Double fingers-crossed that this latest fix is the solution you've been looking for.
Rick

[TonyC]

Thank you, Rick. I am indeed glad that my Aries nature does not believe in giving up that easily. Today, though, I didn't have much motivation to do a highway run, what with gasoline going up again after trickling down a few cents last week; so I still have no report on the results, except that the heater still works at low city speeds. So, at least, I did not cause any new troubles with that soldering surgery to the solenoids. With another cold blast rumbling through the area I probably won't be doing much driving for the next few days unless I have to, and then only remaining within town. Maybe come next weekend I'll give it that highway test.

But as for Bazil LaRoche's case, he did report on the Facebook group last night that his custom-installation of an aftermarket solenoid worked like a charm, curing his problems completely. That is good, at least for him. So, here's hoping that my own diving into the solenoids makes a difference and expels that gremlin. If it doesn't, then at least I have an idea of what type of solenoid to hunt for on E-Bay (Bazil gave me the Amazon listing he used for the solenoid he installed, but I use E-Bay, not Amazon)...or, if I dare try to make the road trip to Florida with an ice-cold heater, maybe I'll carry the spare box with me, swing by LincolnLand and see if they can refurbish the control box. I figure that, if they advertise refurbishings for the smart boxes of the ATCs, they ought to be able to refurbish the dumb boxes of the manual systems.

In any case, I am now convinced that the cause of the problem has always been inside the control box itself; in fact, both of them, my original-original and the replacement I got. Whether it's fixed now or not remains to be seen; I hope so, as I really have no desire to try driving 1,100 miles with no heat, as I don't want to suffer a second fatal heart attack, this one caused by hypothermia.

---Tony

[TonyC]

Highway test done today. Bottom line: Nothing has changed.

However, I did make some detailed diagnostic observations, which now make me wonder if I should look elsewhere. When the hot air went cold again, I turned around and went back to town, leaving the system on the whole time. When I parked in an empty lot, with the air still ice-cold and the controls set to max heat, I opened the hood to observe the vacuum operation (or lack thereof) of the involved components. To my surprise, the blend door was fully opened to the heater core; yet the air was still ice-cold. On a hunch I pulled the hose to the heater valve, which then depleted the vacuum supply to the blend-door servo, plugged the fitting with my finger, and watched the blend-door servo open the flap again. I then refastened the vacuum hose for the heater valve, and the air started to get hot again. It is now making me allude back to George's last suggestion; he asked if the two hoses to the heater core felt different, but I never actually tested them...and now I know I could have and should have, not by touching them but by pointing a thermometer at them (I keep forgetting that I have an electric thermometer on hand for just a job like this). It now appears that the problem is not vacuum cut-off or depletion through a defective solenoid in the control box, but instead through the heater valve. Being that this valve is new-ish (I bought it and installed it over a year ago, when this problem first started up), I have to question whether it may be defective, or it may be installed wrong...but with the latter thought, I did install it the same way the old one was installed. Of course, that may not necessarily mean that it's correct; but the way I have it installed now is the way Dan had specified a year ago: The perpendicular side fitting on the intake junction block side, and the main straight (or bottom) fitting to the heater core. With the former thought, the diaphragm for the valve takes and holds vacuum at a high level....but, could there still be a further internal defect jamming the valve mechanism?

So, what to do about it now...? Get another heater valve, just in case this one has internal defects? And why does this happen only when I build up to highway speed??

---Tony

[tomo]

I would connect my vacuum gauge to the hose going to the heater temperature valve and drive the car at highway speeds to see what is going on.

The squirrels running around in my head are telling me that the heater valve is closing partially highway speeds and then sticking in that position. When you removed the vacuum source, the valve closed fully and then opened fully when vacuum was restored.

[frasern]

My squirrel is thinking weak spring or diaphragm in the valve, or it was designed to flow the opposite direction from the factory one. The water may be closing the heater valve at higher RPM, causing it to bind up until both water and vac. drop. To isolate the valve from other influences, perhaps try driving with your vac. pump attached to just the valve, holding 12". If it goes cold, release vac, then re apply. If that doesn't help, try it again with the trans in neutral and the eng. at idle. If it works, you could make your trip like that, and fix it properly in the spring.
Edit; Or just reverse the valve and try that.

[TonyC]

Good conjectures, both...just what I was thinking myself. I was also thinking of another means, a bit more involved, to confirm a defective heater valve: Drain enough coolant to remove the valve from the car without extensive mess, remove it, cap off the vacuum tee, connect the hose to the heater core directly to the junction block, refill the coolant, then do another highway run. Take it completely out of the equation, in other words. If the hot air stays hot then, that would certainly confirm a defect in the heater valve. And if that works, maybe that is something I could learn to live with for a short while, like for that road trip, then see about applying a proper fix when winter putters out.

Looking at my ignorantly presumptuous posts at the beginning of this thread, I now feel like I've come full circle, and continuing that never-ending ride. But, maybe, had I thought about removing the heater valve completely from the equation in the first place, then this thread might have been limited to one page, like it should have been. Also this has made me realize that my reading comprehension is at an all-time low, that I have to read recommendations several times before I can really give better responses. Embarrassing.

---Tony

Follow-up, 25 Feb: Today I bought a brass 5/8" splice at the hardware store. An elbow would have been nicer, but they did not have any elbows of any kind in 5/8". This splice should work, though, if I remove the heater valve from the short hose at the junction block, keeping that hose in place...which I want to do, as making that hose watertight on the block fitting is always an issue after every removal. I intend to do that job tomorrow; since it will be a bit warmer than it has been, I'll do it at home instead of paying extra for a bay at the auto center. This job will not require any special conditions that only the auto center can provide; besides, I prefer to go there only once this weekend, for a job I do need their services for, unrelated to the heater issue. on my latest plan of attack...which still feels like I've come full-circle, even though I did not think of doing exactly this sort of thing last time I was there.

[TonyC]

26 Feb: Bumping again, new update.

Well, all, as previously advertised, I took the heater valve completely out of the equation today and did another road test. As Anakin Skywalker once said, "It's WORKING!! IT'S WORKING!!!" I did a 60-mile round-trip, cruise set at 65mph most of the time; the hot air stayed hot, except for when I adjusted the temp dial for cooler settings to test the operation of the blend-door servo. Air went cold at the coldest setting, warmed up at halfway setting, then back to hot at the hottest setting, just as it should. So, I found the gremlin's hiding place: The heater valve.

I still cannot quite figure how this valve, which is just over a year old, could have such an internal defect that it would close off the coolant flow at highway speeds despite vacuum pulling on the diaphragm as it should. But, it did. When I got it out, I even took it indoors to give it a bench test: I connected my vacuum pump and ran water from the kitchen tap into one end of the valve. With no vacuum, the water poured out of the one end but not the other. When I applied vacuum, the valve opened and sent the water out the other end. Reversing that test, running water into the other end, yielded the same results. Anybody with good mechanical background would come to the conclusion that the valve is operating properly, right? Well, in my case, wrong. This thing certainly has an internal defect, one which I doubt anyone else may have experienced. Now we all know that heater valves can have even worse defects besides (and beyond) a faulty diaphragm, to cause trouble.

I think my next step might be to buy a new piece of heater hose to run between the intake junction block and the heater core, just for peace of mind for the upcoming road trip. I did notice that the short hose that went between the junction block and the heater valve has some bloating to it, and I do not want to be worrying about a potential bursting while on the road (although I think that a constant, full-time flow of coolant would mitigate that risk, why gamble on that?). I won't worry about getting a new valve right away, since this mad-scientist cobble-fix seems to work just fine as-is; besides, right now, I don't need the worry about a new valve having exactly the same defect. I've been without proper heat in the car for too bloody long, so I'm going to milk this success for all it's worth. The styrofoam insulation I glued to the blend door, when I replaced the heater core several years ago, seems to do a very good job at keeping hot air from bleeding through at the coldest setting, so I really should not need the heater valve to do that job.

Final thought on this, just in case anybody in the future suffers the same problem I did, I do think that all the other avenues I pursued to dead ends could in theory cause or contribute to this sort of problem. Diagnosing all the vacuum components and inspecting all the vacuum hoses connecting them is a wise move. If anything comes up as faulty, fix or replace it. If you can remove the control box and get into it, it's also a good idea, at least to see if anything is visibly faulty inside and needs fixing or replacing. I think even checking the electric controls is a good move, considering what I discovered regarding that sprung-contact "heater switch" at the control head; I now know what it's supposed to do and how it does it. But, actually, with my own experience as a guide, I would recommend checking the operation of the blend door first, see if it is in fact wide open with the system on, set to max heat. If it is and the air is still ice-cold, then that should tell you that the control components are in fact working, meaning that the heater valve is most likely the cause of your problem, even if a vacuum test seems to indicate that it's working as it should. Remove it, literally, from the equation just like I did; the air should finally stay hot by this step, regardless of speed you may be traveling. If it does, then you've found the problem. Just remember to cap off the 1/8" tee fitting for the valve's diaphragm if you run without a valve, even temporarily; if it's left open, the vacuum supply to the blend door will be depleted.

---Tony

[TonyC]

Bloody server, duplicating stuff. But something just occurred to me: Today marks the anniversary of the engine's coma. What a way to commemorate it! Engine is running again, and today I found the gremlin in the heater that was aggravating me even before that coma.

---Tony