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My opinion, and experience (different from some who also have equally valuable solutions) is that the inexpensive oldsmobile or whatever it was valve is the best value for time, money, and functionality. It works better than the original, is a direct replacement. I nearly froze to death driving a bought 928 across the Siskyous one January because the heater valve had been ziptied closed, and we had no tools to get to the valve on the drive home after purchase. Ziptie is at best a very temporary fix till you get a new valve in there.
Remember that ziptieing the broken valve also allows a vacuum leak which affects everything from ignition advance to HVAC flaps to automatic transmission.
Unless someone has been in the vacuum system and goofed it up, it will do no such thing. HVAC and Engine vacuum systems are totally separate.
Unless someone has been in the vacuum system and goofed it up, it will do no such thing. HVAC and Engine vacuum systems are totally separate.
And even then it’s the vacuum solenoids that switch and release vacuum not the rubber-diaphragmed actuators. The only way to create a vacuum leak by zip-tieing the heater valve is to remove the rubber vac line elbow in-process and forget to re-attach it.
The Ford Escort heater control valve (HCV) is a drop-in for the original, and requires only some minor electrical surgery with the relay and solenoid wiring to work with the original HVAC control. It swaps the HCV function to a "fail-closed" from the original "fail-open" configuration. The valve stays closed until the contacts in the setting motor close. With the relay inverting the logic, the vacuum solenoid actuates and applies vacuum.
At one point I had all of this sketched out, but didn't follow through since the zip tie was working just fine while we were in SoCal. "Heating season" there was maybe a month or two in the dead of winter, when morning temps might be a frigid 45ºF. The rest of the year is AC season with the the HCV tied shut. Now in the wilds of central Oregon, summer overnights are in the 40's so there's ample opportunity to use both heating and AC in the same day. No more zip ties, and everything in the system is working as originally intended. BTW, 42º overnight, headed for a dinner-time high in the low 90's. If the current temperature isn't to your liking, one need only wait an hour or three. Single-digit RH numbers in the afternoon so no steam-room effect either.
I am thinking that a manual heater valve (picture below) would provide a good solution? installed in line, reward of the current heater valve,
and simply shut off the valve, eliminating any water from entering the heater core. if the weather gets cooler (rarely here) simply open the valve.
has anyone done this? any downside, besides not having heat or defrost???
I am thinking that a manual heater valve (picture below) would provide a good solution? installed in line, reward of the current heater valve,
and simply shut off the valve, eliminating any water from entering the heater core. if the weather gets cooler (rarely here) simply open the valve.
has anyone done this? any downside, besides not having heat or defrost???
That's certainly an option. The hoses to and from the heater are accessible where they make the turn into the heater core. Be sure to install the valve in the same hose that includes the current valve, as that's the most direct path for heat to migrate through from the top of the engine. Put the valve where you can most easily access it between seasons.
Just received a PM from a user asking about the Escort valve function. My original suggestion was to add the "normally-closed, vacuum-to-open" Escort valve in series with the factory valve. Connect the valve to manifold vacuum. That's the same vacuum used for the fuel pressure regulator and dampers. That vacuum goes away instantly when the engine is stopped, causing the Escort valve to close at the same time the factory normally-open 928 valve is opening as its solenoid valve relaxes.
PM question was around the effects of varying manifold vacuum as you drive. We are really most concerned about the Escort valve closing when the engine stops. In between, the manifold vacuum varies inversely with engine load. Under high load, vacuum goes low enough that the Escort valve might close. For us drivers in America, extended high-load operation isn't realistic. High loads are short bursts of acceleration, then cruising at whatever the speed limit might be, give or take. During those brief high-load periods, the valve would reduce or eliminate coolant flow through the heater. Flow would come back as soon as the throttle was no longer on or near the floor. I'll speculate that you wouldn't notice the momentary reduction in hot water flow. But you might.
Adding an inverting relay to the mix allows you to replace the factory valve with the Escort valve. The valve would be closed until the system demands heat, and be closed at all other times including when the engine isn't running. The Escort valve may or may not be more robust than the factory valve, of course. Having the two valves in series would do nothing for leakage through the factory valve. Inverting the signal to the solenoid would place all the sealing duty on the Escort valve of course, since the factory valve wouldn't be used at all. I guess we'd find out if it leaks, the same way we find out with the factory valve. I'd be adding a small SPDT relay inside the control head for this modification, by the way.
not sure I am comprehending the logic in using the manifold vacuum as opposed to either the booster vacuum OR using a Tee in the heater
valve vacuum line. if I use the heater valve vacuum source, wouldn't the solenoid bleed off all vacuum with key off?? and then the OEM valve
would be open, and the escort valve would be closed??
It will have vacuum while the engine runs, and it will open. The factory valve will open and close as needed to regulate cabin temp. When the engine stops, manifold vacuum immediately goes away. the Escort valve will close, isolating the heater core from the engione while the engine is stopped. With key off, the factory valve opend. The closed Escort valve will block heat migration into the heater core.
Under certain very limited high-load circumstances, the Escort valve may go partially of even fully closed as manifold vacuum drops. But it will come right back, usually faster than you npotice the momentary reduction in heat from the heater.
If you want to make it technically pure and have a S4+ car, add a T and a short section of hose between the brake booster and the little check valve to the rest of the accessory vacuum system and the reservoir. Connect the Escort valve to that T. It will have full vacuum to open whenever the engine is running, and will go closed on engine stop. That particular place has the benefit of the venturi between the throttle body and the intake, so vacuum is maintained by velocity even under high engine load. IMO this isn't necessary.
I’d like to add a flappy type solenoid valve in series to the vacuum feed to the water valve (between the AC solenoid valve & the actuator). Important to understand that these valves (like the AC solenoid valves) are 3 port devices: vacuum in, actuator connection & bleed port.The actuator is then connected either to the vacuum source or to the bleed port (usually open to atmosphere) depending if the solenoid is activated or not respectively. With a series flappy type solenoid you can quite easily plug the bleed port which creates potentially a 'vacuum sustaining' valve. However for it to really work this way you also need a way to ensure it turns off before the main AC solenoid for the water valve turns off.
Practically this is most easily accomplished by controlling the series (flappy type) solenoid with an ignition source, and modify the HVAC head unit (blower relay) to turn off with accessory power. With this configuration (assuming the heater valve actuator diaphragm doesn’t leak) when the car turns off the heater valve will stay in whatever mode it was in before the car shutdown. In winter heating mode it will stay on, and in summer max cooling mode it will stay off. Given some vacuum leakage the valve may eventually open after some hours - but by then the engine will be at ambient temps anyway. The beauty of this is you don’t need to change the stock valve or solenoids, and this new valve is easy to add in the middle of the regular line routing - say in the bulkhead area. But you will need to change the control of the HVAC/Blower Relay from ignition off to X-Bus off. A good thing is that the default failure mode behavior (e.g. no vacuum or a dead HVAC system) is still to allow heat - as in the stock case.
I haven’t done this mod yet - but I think it’s the best solution overall. Works well for winter or summer modes without any manual seasonal user intervention, the summer or winter mode is just based on how you are currently using the HVAC system - you will just naturally get the mode you'd most likely want.
What you describe would work. The little solenoid valves typically seal pretty well. If there's a concern about it leaking down too fast. add a reservoir of some sort between your new solenoid and the valve.
This is all in the quest to find something that's minimally invasive and easily reversible. As EE's we migrate towards electrical solutions. In my spare time I do a little process work, so I also get to look towards valves and "plumbing" solutions. Ultimately it will come down to how comfortable an owner is with the work needed.
I dunno. Call me a simpleton. Get it working as it should from the factory and go forward from there.
Sean - ahh no! - it's just too too hot in Phoenix to want to get blasted with more warm air. It DOES already work as it should from the factory - and I really don't like that...so I did indeed go forward from there.
08-13-2018, 03:16 PM
