Manual A/C Heater Problem

[TonyC]

Hi, all,

I have a problem, and it's gotten to the point that I want to reach out to see if veterans have any experience with it. Frankenstein's heater has started malfunctioning. Now, I'm talking about a manual A/C setup, NOT automatic. Here's what I've determined so far: The blend door is operating normally with adjustments to the dial. However, cold air blows out the ducts most of the time; for short, sporadic moments the air is warm but then switches to cold. This tells me there is something wonky with the controls, so now I'm focusing my hunt on that. There is a vacuum regulator attached to the dial assembly, and that is also working normally. There is also an electric contact-point switch attached at the same spot as the vacuum regulator, which the manual refers to as a "water valve electrical switch"—it's basically a spring-loaded contact point with two purple wires that plug, presumably, to the control box on the firewall. This is the primary focus of my attention right now; unfortunately the manual does not give a whole lot of assistance where its function is concerned.

Here's what I know about it: It has an insulated rubbing point that is supposed to rub against a dowel in the dial; that dowel pushes against the rubbing block when the dial is rotated to the "COOLER " end of the scale, releasing when the dial is turned towards the "WARMER" end. In its free state, the sprung contact point is touching a stationary contact point; when the dowel rubs against the rubbing block, the spring pops that contact point away from the stationary point. I'm presuming this switch is supposed to command the control box to switch to heating mode, but the way this switch is operating sounds backwards. I would think that when the points are touching the control box will be in the heating mode, and when they are not touching the box is in cooling/vent mode. Something else I noticed in my diagnosis today: At the "COOLER" setting, the air seemed a bit on the warm side, but when I turned the dial to the "WARMER" side the air got cold. One would think I just have that switch on backwards, but it installs properly in only one direction. So, the $64 question is, what am I missing here?

Or...maybe I'm not understanding what that switch does, actually. Maybe the controls are all fine, and it's the control box itself that has the gremlin?

Or...something I noticed in diagnosing the heater valve: It's supposed to open at 5" Hg. I applied a vacuum pump directly to the valve; I attained 5", but it didn't stay at that level. It dropped to about 2 to 3" when I stopped pumping. I'm thinking that it should stay at 5" once I got to that level. Maybe in fact the heater valve is malfunctioning?

Maybe this question is best directed to one of the Johns—either Brewer or Cashman—but I want to see if anyone here has had experience with this system. I know it's a long shot, since most cars were fitted with the ATC option which does not have this setup.

---Tony

FOLLOW-UP, 29 December 2020: I have the dash partially taken apart right now, trying to yank the "brain" from its mount. It is not easy, with such a bulky shell jammed up against wiring and ducts. The box has exactly the same shell as the ATC brain, but it's not an ATC system; in fact, I shined a light into it, and I noticed that at least 75% of the inside is empty space! What I don't get is why the engineers would use an ATC shell to house the "dumb" components of a manual system—I mean, seriously, what's the ruddy point of that?!

But now, I'm wondering if I may be chasing the proverbial wild goose by going after the box. Note what I stated about the behavior of the heater valve; I'm beginning to wonder if that may be the cause? If it is, that means another replacement; but this one is only two or three years old. Well, defective parts can be had, I guess...

UPDATE, 31 December 2020: Well, I aborted the removal of the brain yesterday, based on the behavior of the heater control valve which came to mind just yesterday. To recap, I applied a vacuum pump directly to the valve to see how it behaved. I only got to about 7" Hg when I pumped it, and when I stopped the vacuum dropped to about 2 to 3". I don't know why it didn't occur to me immediately that the valve had a potential problem, which may be why nobody answered my request for input. I can understand that; after all, I'm supposed to be the field expert on these cars and know this like second nature. Anyway, on a hunch, yesterday I put the dash back together and went to buy a new heater control valve at O'Reilly. It came in today, and I decided to test its diaphragm to see how it was supposed to behave. I got to nearly 20" on only three pumps, and it held when I stopped. So that tells me right away that the heater control valve must be the cause of my problem.

There's something else I noticed as well: I may have routed the old valve wrong three years ago, which might explain why it failed after so short a time. The routing I have right now is as follows: The outlet hose from the rear junction block is attached to the valve's side fitting, and the hose to the heater core is attached to the longitudinal fitting. I am not 100% sure whether the hoses need to be reversed; if so, that means I had that old valve routed wrong for three years—big goof on my part. The shop manual does not give clear guidance on how the heater control valve is to be installed, save for one drawing which suggests that the current hose routing is in fact correct; I still need input from someone to know if it is. I've replaced the visual aids of this message with new shots to help explain my current theory.

[TonyC]

Bumping for attention; updates included.

---Tony

[papawayne]

Tony, I'm replying to you just to be friendly, and because no one should not get a reply. Stuff like this is way beyond my skill level. Magic boxes and the such absolutely mystify me. It is time like this when i need professional help. (Just ask my wife, she's been trying to arrange professional help for me for years!) I have faith that you will eventually figure this out, so best of luck to you, have at it, you will get it...Wayne

[rick]

Tony, I too have been following along with interest.

It seems as though you may have solved your own problem. Hope so. Looking at the way my '61 is configured there is a similarity to the hose routing to the heater control valve. But the '61's system is a different animal. Let us know how it works out.

[LC67Vert]

Tony, I have a '67 with a manual HVAC system as well. I think the routing of the hoses in your photo is correct. I just went to the garage and took two photos of mine, one from the left side (like yours) and the other from the right side. Aside from the embarrassingly corroded condition of mine (!) I think the hoses are hooked up the same way as yours is in your photo and my heat works fine. I can easily regulate from cold to warm and back by turning the temperature knob.

[TonyC]

Thank you, Wayne, Rick, Jeff. At least now I'm 100% confident that the heater control valve is installed properly. This mystery is really aggravating for me, but I do have confidence in my stubbornness, so I will figure this out one way or another.

But that has to take a back seat now; today I had something else pop up, literally. I went to put in a bit of gas to replenish what I burned last night looking in vain for a drinking establishment to toast the passing of 2020, and when I got to the station a huge cloud of steam came billowing out of the engine bay through the hood and grille. The coolant bypass hose blew out. I'm thinking that maybe the thermostat must have seized up in the closed position, causing too much pressure and causing the hose to pop; that is usually the cause of that sort of thing. But, at least that happened at my regular gas station this afternoon, and not in Salina last night!

I did not have everything I'd need to do a full repair, so I had to resort to a field-repair. Thankfully, the hose burst at an end point and not right in the middle; I was able to remove the popped end from the intake manifold fitting and re-clamp the rest of the hose. But it's seriously bloated and spongy-feeling, which means I need a new hose. Thing is, I can't remember the diameter of that hose; anyone know if it's 3/4" or 7/8"? I know it's one of the two. If it's 3/4", then I have that on hand; if it's 7/8", then I need to make a trek to get some. Actually, I'll have to make a trek anyway, as I'll need a new thermostat gasket (I have a new thermostat already). Still grinds my gears that I had to spend $42 on new antifreeze (the diluted version, on top of that!), but it is what it is.

I don't know whether a jammed thermostat would have any effect on the heater; I doubt it, at least until the bypass hose pops...but the heater failed me over a week ago, so I doubt that had anything to do with totally unheated air being blown into the cab. After I repair that engine problem properly and put in an order for new med supplies, then I'll get back to diagnosing the heater. I'll go by the shop manual's instructions for that.

---Tony

[action]

Thankfully, the hose burst at an end point and not right in the middle; I was able to remove the popped end from the intake manifold fitting and re-clamp the rest of the hose. But it's seriously bloated and spongy-feeling, which means I need a new hose. Thing is, I can't remember the diameter of that hose; anyone know if it's 3/4" or 7/8"? I know it's one of the two. If it's 3/4", then I have that on hand; if it's 7/8", then I need to make a trek to get some. Actually, I'll have to make a trek anyway, as I'll need a new thermostat gasket (I have a new thermostat already). Still grinds my gears that I had to spend $42 on new antifreeze (the diluted version, on top of that!), but it is what it is.

---Tony

MPC says C3TZ 8555 A Water by-pass hose is 7/8" X 1 1/2"
For all 65 to 68 430 & 462 engines

A stuck thermostat usually results in the cooling system over heating as very little coolant leaves the engine to go to the radiator. Would show up as the warning light coming on at the instrument panel.
Since a closed thermostat is a normal position when coolant is not up to temp, excessive pressure is not possible. The system was designed for the pressure of a closed thermostat.
Spongy hose is well past it's service life. This is the cause of the concern. Time to check other hoses as well. And fan belts.

Action

[frasern]

Happy new year Tony, and all others.
My Lincoln has heater, without air, so I have remained silent, however, I am now thinking your problem is in the heater. Both systems are rather simple, but blending them isn't, so that is naturally where you first look. It could be that the heater is marginal, and as it fluctuates, it feels like a blend issue.
I would try back flushing the heater core, by itself, and see what comes out. Go back and forth between the two hoses. It could be mostly blocked, and in your climate, that hasn't been an issue. (We sure notice it up here!). Go slowly at first, it's possible to rupture a seasoned core. Also, if your hoses are weak, they could be collapsing, due to the resistance of a slow flowing heater core, making it feel even more like a wonky valve.
Another thought is a vacuum leak in an unrelated system, bleeding off your vacuum, seemingly at random.
Just some ideas I'm floating out there, not something I have experienced. Good luck.

[tomo]

If my memory is correct, the hose going to the heater core connects on the port going to the side and the hose coming from the heat source goes on the port that you can see the actuator. This allows the actuator to control the flow of coolant. Hooking it up backwards would not affect the vacuum diaphragm life, just make adjusting the heat more unreliable.

The hose going into the control valve looks like it is ready to fail also. Notice the bulge behind the clamp and what looks like a tear in the bulge.

[TonyC]

Thank you again for all the input, if at least well-wishing in solving the mystery. If/When I do, I promise to post my findings, just in case somebody down the road suffers the same failure for the same reasons...which is not likely, I know, all the weird s**t has to happen to me.

MPC says C3TZ 8555 A Water by-pass hose is 7/8" X 1 1/2"
For all 65 to 68 430 & 462 engines

Thank you, Action, for verifying that. That confirmed my measurements yesterday for the I.D. of the bypass hose; so, that means I have to risk another local trip to get some.

A stuck thermostat usually results in the cooling system over heating as very little coolant leaves the engine to go to the radiator. Would show up as the warning light coming on at the instrument panel.
Since a closed thermostat is a normal position when coolant is not up to temp, excessive pressure is not possible. The system was designed for the pressure of a closed thermostat.
Spongy hose is well past it's service life. This is the cause of the concern. Time to check other hoses as well. And fan belts.

I have to partially disagree with that. The system generates pressure just by the water pump, and adding extreme heat to that only generates more pressure; that's simple physical science, and excessive pressure is possible, otherwise hoses would not burst even when they're ten years old. When coolant is up to temp, and the thermostat remains closed, that's a recipe for disability (or disaster for someone who has no tinkering skills and who tends to panic at ever unpleasant surprise in life). I have no doubt that the system itself is designed to well withstand that sort of situation, but hoses are not included in that. As for the other checks, that's an academic critique, as I have already checked and replaced every hose and belt within the past year, save for the bypass hose...oh, and the lower radiator hose, which does seem to be getting on in years .

---Tony

[action]

I have to partially disagree with that. The system generates pressure just by the water pump, and adding extreme heat to that only generates more pressure; that's simple physical science, and excessive pressure is possible, otherwise hoses would not burst even when they're ten years old. When coolant is up to temp, and the thermostat remains closed, that's a recipe for disability (or disaster for someone who has no tinkering skills and who tends to panic at ever unpleasant surprise in life). I have no doubt that the system itself is designed to well withstand that sort of situation, but hoses are not included in that. As for the other checks, that's an academic critique, as I have already checked and replaced every hose and belt within the past year, save for the bypass hose...oh, and the lower radiator hose, which does seem to be getting on in years .

---Tony

You can disagree but do follow the simple science. The burst strength of a standard heater hose approaches 100 PSI.
While the pressure cap allows system pressures to 14 or 16 psi, if the pressure got to that point, the cap would release system pressure down to a couple of PSI for the whole system.
I am pretty sure the water pump can not generate anything over 5 PSI, if that. The pump is not sealed like an oil pump and the thermostat even when closed, still lets some coolant pass. And most of thermostats have a bleeder opening.
Which leaves heat that can generate some pressure, but you did not state the engine coolant warning lamp came on. Which would indicate excessive heat. But let's say the warning lamp doesn't work in your car and it was possible that the cooling system pressure got over 25. (it's not possible) The heater core can not handle that kind of pressure. It is only designed to handle about 15PSI. Neither can the radiator. The weak link in well maintained cooling system as far as pressure goes is the solder joints of the heater core or the radiator, not the hoses. A hose will expand under pressure. A solder joint just breaks.

Link for heater hose PSI
https://ph.parker.com/us/en/heater-hose-series-7186-1

Link for heater core removal and states operating pressure of heater core
https://ricksfreeautorepairadvice.com/h ... er%20hoses.

Action

[TonyC]

Well, academics aside, here's the latest on that story. The bypass hose blew out again today, but thankfully not before I was able to get a new hose. There was a bit of a complication with that: No parts store carried bulk 7/8" hose, not even NAPA; they had 3/4" and 1", nothing in between. The attendant at NAPA was, however, able to sell me a piece of shaped 13/16" hose that applies to a different car; it had just enough straight hosing to it that I could trim and use, although I had to spray some white-lithium grease onto the fittings to coax the piece on. So that issue is temporarily fixed; I also added the new thermostat I had on hand while I was at it. E-Bay does have sellers of 7/8" heater hose, so I put in an order for a foot of that. It doesn't help me today, but it will help when I am ready to perform the cylinder-head swap in about a month...and since I only need about 3" of that, I will have a very good stock of that size hose for a long time. If anyone is ever in need of 7/8" hose for the bypass route, go to E-Bay.

---Tony


FOLLOW-UP 1, 5 January 2021: Well, all, I finally succeeded in pulling out the control box; although a bit of a bear, I'd say that it was more of an adolescent cub. I do have pointers for those out there who may consider a similar job. First, the shop manual states not to disconnect the vacuum hoses or electric harness from the engine-bay side of the box until after it's pulled off its anchor point. I can tell you that those instructions should not be followed; you do need to remove those first, or you'll never get the box off. The three hoses are all of different sizes, so there should not be much confusion in reinstalling them; however, you can do what I did to make it easier: Number the hoses. The big one at the top of the triangle configuration I numbered "1"; the smallest hose, at the lower-left of the triangle, I numbered "2; the second-smallest hose, at the lower-right of the triangle, I numbered "3." Yes, there is also a wiring harness on that side, right under the triangle of hose fittings, which was not very easy to unplug with the brake booster still in place, but possible. Once I got that off, which took me a good 45 minutes of incremental pulling, the "brain" felt ready to slide off...except that a wiring retainer clip, which was attached by a bolt on the shell, was still interfering even with its attachment bolt off. I was able to wiggle it off the wires it was wrapped around, and I decided to just leave it off as it was more of a nuisance than it was worth. Then the box came out. I discovered that the screws that hold the shell together had really wonky-looking heads on them—three slots configured like a Benz ornament, with a raised section in the center. I mean, seriously, who has ever seen, let alone had, a screwdriver for such a screw head?! I did manage to get them off by pressing a flat-head against the slots and tapping them 'round with a hammer until they turned just enough for pliers to finish the removal. For good measure, I took my Dremel with a cutting wheel and cut in proper flat-head slots to make it easier to reinstall them...and for any future disassembly that may be necessary.

So, you know what I found in there when I got the shell apart? NOTHING. The setup is actually quite simple compared to the automatic brain (see attached pictures), and there was nothing inside the box that suggested a contributing factor to the failure of the hot air; all the vacuum hoses inside were not only fully secured, but also as pliable as if they were new. The wires were all intact and properly attached. I did notice a bit of depositing at the contacts, which would be natural to see after 54 years, so I took my cleaning wheel to the contacts, cleaned them off one by one, added dielectric grease to each, and reassembled everything. The box is now back in place; I haven't bothered testing the system today, but I have very serious doubts that will have made any difference...except at least in ruling out yet another component. If the heater still doesn't work tomorrow, then the next step will be to perform a vacuum test per the shop manual's guidance, then probably pull out the heater core and check it for plugs to the coolant flow (but that will have to be done at the auto shop because I don't have a garden hose to stick in it).

But, on a good note of news, the 7/8" heater hose I ordered three days ago arrived today, so at least I have that on hand for the next huge project.

FOLLOW-UP 2, 11 January 2021: I posted a request in the "Wanted" category, and then I came across a hit outside the Forum, via a Facebook group. So I have a replacement brain on the way. I did a bit more studying of the wiring schematics using my '67 shop manual (because the '66 manual does not have a listing for manual-A/C wiring schematics), and it looks like there is no discernable difference between the control boxes of the non-A/C system and the manual-A/C system. There is a difference in the two systems, naturally; but it looks like the associated wiring for the A/C goes entirely around the control box, not into it. Since the brain only regulates vacuum to the numerous ventilation hatches, and the hatches are exactly the same in both systems, that would make sense. Maybe that will expand my options, just in case the one I bought yesterday is also defective. But I'm fairly sure my guess on the cause of failure is in the brain: It regulates the flow of vacuum to the numerous hatches via solenoids, and the schematic indicates that one solenoid is committed to temperature regulation, likely supplying vacuum to the blend door and heater control valve. The schematic does not specifically label the solenoids, unfortunately, it only explains each one's purpose; so I don't know which is which...but it should make for an interesting mini-exploratory surgery when I swap the brains out and verify whether the problem has been cured.

[TonyC]

Bumping my own thread to share my latest diagnoses. Unfortunately, the gremlin has not been expelled yet, but I did a bit of fiddling to get at least partial heat operation. After said fiddling, the current operation is as follows: With the dial set at the coldest setting, I get heated air when I'm driving around town. However, when I get on the highway, I notice that the heat starts to fade and get colder; when I reach 60 mph, the heat stops entirely and blows cold air. To get heat back, I have to drop back to city-traffic speeds, turn off the system for at least a minute, then turn it on again. This has to be due to malfunctions in the controls. Before anyone suggests a vacuum-supply problem, I have thought of that: First, I've had vacuum-supply problems for years and never experienced this problem with getting heat. Second, at highway speeds, everything else that is vacuum-operated (auxiliary power for wipers in the wash operation, brake booster, cruise control) still works as it should. Only the heater valve and temperature blend door lose their vacuum supply; the rest of the HVAC hatch servos are getting vacuum and operating normally.

I got a replacement control box, tested the reservoir, did a continuity check of the pushbutton cluster, and even did a necessary reroute of the vacuum plumbing in the engine bay, none of which made any difference to the issue. Right now, I'm focusing on the control panel, which I know has problems in it: The vacuum regulator on the control shaft was not adjusting vacuum the way it should, which doesn't make sense because it was a NOS part when I got it two years ago; I bypassed it, connecting the two hoses that go to it directly to one another, which helped a little bit but not completely. Also, the "blend door and heater water valve switch," a contact-point switch with two purple wires screwed into the same spot as the vacuum regulator, is operating backwards, switching on at the coldest setting and switching off when warmer settings are dialed in. I think what I need to do about that is find somebody who happens to have a spare manual-A/C control panel with its hardware attached, minus the pushbutton cluster (mine is working as it should), to sell to me.

Besides my hunt for a replacement control panel, there was something I discovered inside my old control box, which I know is also an issue with its replacement, and I need to know how big an issue that is. The solenoids inside the box were originally fitted with filters of some sort, a round disc over each hole in the center of each solenoid. They were not visible in the pictures I originally posted, so I'm posting new pictures to show what I'm talking about. Those filtering elements have deteriorated so badly that two of them are literally gone, and the other two cannot be far behind. I am wondering how much of a contribution to operation those filters provide—they must have been put there for a reason. If they do in fact serve a purpose and need to be there for the box to operate properly, that means I need to place new filtering over those holes, meaning I need to find appropriate filter material to do that job. If anyone knows one way or the other how important that is to proper operation, please chime in. Also, please feel free to chime in if you happen to have a spare manual-A/C control panel, either here or via PM.

---Tony

[action]

I believe those are vacuum bleeds.
Meaning when selected, those "valves" bleed off vacuum in those vacuum circuits as needed. Once a valve is turned to close a vacuum signal the bleed off valve lets in air so the vacuum signal is no longer available on that vacuum circuit.

The filters over the holes are designed to prevent dust from inside the vehicle from getting into the control system.
However I doubt the engineers considered these vehicle to be operating decades. The foam was likely expected to last 10 or 20 years.

If my assumption is correct, the old foam may now become the debris that it was designed to filter out!
Some disassembly and cleaning may fix that issue. And anywhere down stream (towards the engine) that has valves especially ones with small clearances may benefit from cleaning.

The interior of a vehicle does not have as much dirty air as outside of a vehicle. And after 5 decades of sucking air with some time of unfiltered air, there may be issues.

And all of that is a guess on my part as I have never disassembled a system.

Action

[TonyC]

Thank you, Action, that does make sense. Granted, this is also a first for me; although I'm pretty sure John Cashman must have had a great amount of experience with this sort of thing, trying to get his input will be difficult, I know. I'm wondering now if, after all that time, perhaps their deterioration may contribute to the problem I'm having especially with the heat cutting off at highway speeds (the solenoids which I suspect to be the heat activation are missing their respective filters in both boxes). Whether they are or not, I think it best to replace them with new filtering material. Cutting new discs and gluing them into place on the solenoids is not an issue. My current issue is, what to use? The originals were made of similar foam material used on some headphones for cushioning, or as air filters on older vacuum cleaners. Should I look for that, or would pieces of muslin work satisfactorily? I'm asking because I'm not quite sure where to find the former, although it should be commonplace just about anywhere. The latter, though, I have a very good stock on hand, used as repair material for torn leather.

---Tony