ConcoursMustang Forums
1st Generation 1964 1/2 - 1973 - Questions & general discussions that apply to a specific year => 1968 Mustang => Topic started by: 68 GT on April 04, 2024, 03:36:25 PM
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My 68 coupe came with factory AC. I do not have the AC hooked up, but I do have a vacuum operated water valve mounted on the firewall about where the heater hoses connect to the heater core. I have a vacuum canister mounted inside the passengers front wheel well. I'm replacing all of the hoses and installing a 24? 3 row radiator with a clutch fan and shroud. A cooling system upgrade kit I bought from West Coast Classic Cougar. Since I don?t have AC in my car now, should I not even hook up the vacuum operated water valve? Just connect directly to the heater core?
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No you cannot delete that valve. It is needed to turn off the heater.
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My 68 coupe came with factory AC. I do not have the AC hooked up, but I do have a vacuum operated water valve mounted on the firewall about where the heater hoses connect to the heater core. I have a vacuum canister mounted inside the passengers front wheel well. I'm replacing all of the hoses and installing a 24? 3 row radiator with a clutch fan and shroud. A cooling system upgrade kit I bought from West Coast Classic Cougar. Since I don?t have AC in my car now, should I not even hook up the vacuum operated water valve? Just connect directly to the heater core?
No you cannot delete that valve. It is needed to turn off the heater.
You might be able to temporarily remove the valve during the time you have no AC, but as Royce says, "it is needed to turn off the heater", at least in the future. There are a lot (yes boys and girls, it IS two words) of plumbing drawings in the "1968 Mustang Chassis Assembly Manual" you can refer to. At the least, replace the valve with a piece of copper pipe and some hose clamps.
Jim
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If you don't care about correctness, concoursness (Jim, is that a word?) and other nesses, you can delete the valve. After all, cars without AC don't have them, right? In modern terms, the valve is a "A/C max cool" function.
A car that originally had factory AC would take a lot to completely remove all parts that are part and parcel of the AC system. You've mentioned a few things (water valve, vacuum tank vacuum hoses) that you still have. I would guess that you have the AC plenum, AC duct/vents, AC control panel, and other AC gobbly gook under the dash. If you leave the vacuum line to the heater valve hanging like a chad, when you move the cable operated blend door position to full cool, a vacuum switch (which is one of the items probably still under the dash) will port engine vacuum to that hose, so you will want to put a cork in it - figuratively.
It is a challenge to determine where to stop for something like this. Jim referenced "the future", so you might want to consider someone down the road that might want to undo the voodoo that you will do. So if you remove the valve and bracket, put that and the mounting screws in a quality zip lock bag or box, with label and keep it in a place to remember.
To reiterate - the valve does not "turn off the heater" per se. For AC cars, on max cool, it will interrupt engine coolant flow to the heater coil...if everything is working correctly after 50+ years. On cars without AC, which is what this car effectively is at this point, when you move the blend door to full cool, it is bringing in outside air through the cowl vent. There is still hot fluid going through the heater coil. With imperfect seals, some of that heat will leak by. The answer is to shut off the blower and open the windows. Heat still circulates through the heater coil.
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To reiterate - the valve does not "turn off the heater" per se.
Indeed, that is all the valve does. It has not one thing to do with the AC working.
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If you don't care about correctness, concoursness (Jim, is that a word?)
It is now.
- the valve does not "turn off the heater" per se. For AC cars, on max cool, it will interrupt engine coolant flow to the heater coil...if everything is working correctly after 50+ years. On cars without AC, which is what this car effectively is at this point, when you move the blend door to full cool, it is bringing in outside air through the cowl vent. There is still hot fluid going through the heater coil. With imperfect seals, some of that heat will leak by. The answer is to shut off the blower and open the windows. Heat still circulates through the heater coil.
Water always flows thru the heater cores on Fords, whether you have the heater controls on "heat" or "defrost". The valve does stop that flow because your A/C uses the same ducting.
Jim
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Water always flows thru the heater cores on Fords, whether you have the heater controls on "heat" or "defrost". The valve does stop that flow because your A/C uses the same ducting.
Jim
For Fords with factory equipped AC (from and including the 1967 MY and later, possibly earlier on A and B cars), when the cable-operated temperature blend door is moved to the max cool position, a lever triggers a "water valve vacuum switch" (see the attached). This ports vacuum to the "water valve motor" , which closes off engine coolant flow to the heater core. It does not depend on mode (floor/vent/defrost). It does not depend on whether or not the AC mode is active. It depends solely on the blend door position.
Indeed, that is all the valve does. It has not one thing to do with the AC working.
I agree. But since non-AC equipped cars did not have the valve, my point is that it is not required to keep. If it were me, and if it were not failed closed, I would keep it.
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For Fords with factory equipped AC (from and including the 1967 MY and later, possibly earlier on A and B cars), when the cable-operated temperature.......
Actually the valve operates any time the temp control is moved to the HEAT position. It is the only thing that shuts the heat off and turns the heat on. It is necessary and has nothing to do with the AC operation.
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Actually the valve operates any time the temp control is moved to the HEAT position. It is the only thing that shuts the heat off and turns the heat on. It is necessary and has nothing to do with the AC operation.
I'll respectfully disagree with you on this one. Here is why:
1. Logically speaking, if the valve operates when the temp control is moved to the HEAT position (with the way this is written, I take you to mean the "full heat" position) the valve would have to open or close. Of course open to allow flow through the heater coil must be the case in this "HEAT position" scenario. The problem with this is when you move the control slightly away from HEAT in an attempt to temper the air bit, the valve would binarily change state, closing to restrict flow, and you would have ambient (outside) air flowing through the vents. Once the latent heat is removed, there would be no vent discharge temperature difference between "Cool" and "not quite full" "Heat". To summarize, any function if closing the water valve must occur at full cool, not full heat, in order to make blending functional.
2. I found, in the shop manual on page 16-11, and attached here, clearly supports my understanding that the vacuum switch porting vacuum to the water valve is actuated "when the temperature lever is in the maximum cool setting"
3. The second picture is one of a table from the vacuum book, page 1-1, which in chart form says the same thing.
One additional comment is that the shop manual indicates that the water valve will close if, in addition to the cable position (max cool), "the A/C-heater, air distribution control lever is in either A/C position". I read this as though there are some stars that need to align to actuate the valve - namely cable position and control head vacuum control assembly position. That is not my experience on working on these systems and that is not how I interpret the vacuum diagram. The third picture highlights engine vacuum in red, up to the switch that is triggered by cable/blend door position. After that, I change to blue to indicated "switched vacuum" which ends up at the valve. There is no way to influence this signal from the vacuum regulator on the control head.
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You are dreaming. The valve does nothing other than turn the water off and on.
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You are dreaming. The valve does nothing other than turn the water off and on.
+1. Sometimes things can be too simple to comprehend.