heater coolant disconnect

[delco1946]

I know a lot has been written on this, but i still can't seem to find an answer to my question. In anticipation of summer, i want to be able to stop the flow of coolant into my heater. My 1955 ford has a similar problem in that already warm outside air flowing into the cabin gets hotter. Its very unpleasant! I want to avoid this on my truck. I have the basic heater system. Do i put an open/closed valve in the heater hose line? Which one? both? do i have create a system to allow continuous flow through the hoses for the engines health (but effectively allow the heater to be cut off? What valves will hold up to the fluid corrosively, pressure, and hot temperature?

Finally, is it possible to add actual ac in the future? I don't really care if it comes out of the defrost/floor vents ( i don't have face vents).

[jstone4646]

I do not know if this can be done easily per say, but instead of adding bypass valves that could potentially fail, you could just completely disconnect (and plug to keep debris out) the hoses running to the heater core and use a joining connector to just completely bypass it.  Then when the cold begins to come back around just normal it all back up?  Just a thought!

[delco1946]

That is a thought. I wonder though, to do that, id have to drain the coolant each time right? Also, i admit as low tech as I'm trying to go, i would like to simply be able to pop the hood and turn the system on or off depending on weather.

[jstone4646]

Well I do not know for sure if you would need to drain it.  Assuming the motor was cold when you do the swap you may not need to flush the coolant.  You would probably spill or loose a little, but again if the motor was cold, and since you are on the top end of the motor, if you keep the hoses as elevated as possible, gravity should keep it all in place.  But you do bring up a good point, you would not want to leave stagnant coolant in the heater core all summer long, so you would likely want to put some low pressure air through there to clean it out?  Sorry I do not want to give bad advice, but it was just a quick thought!

[delco1946]

i hadn't thought of that. I wonder if disconnecting the heater could hurt it? If i drained it, could its guts rust?

[Gary Lewis]

You might want to check out this thread which discusses that.  And then this page: HVAC Systems and the Heat Shut Off tab and then the Vacuum tab, which is the only one I've populated.

But there are manual valves that will easily do the job.  I'll try to remember to put some info and pictures on the Manual tab on that page tomorrow.

And all of the engines have a bypass system in the cooling system, so you can just put a valve in one of the heater hoses, and it doesn't matter which one.  

[Frank Wyatt]

I agree with Gary in I like the Four Seasons valve{http://www.napaonline.com/en/p/BK_6601294} which recirculates the coolant when bypassing the heater core. It can also be found on some Fords like the Explorer if I remember correctly. When ever I finaly get around to replaceing my heater core, I'm thinking of useing an electric vacuum control vave like this one to operate it http://www.summitracing.com/parts/vta-11542-vus. You can get the bypass valve here also http://www.summitracing.com/parts/fss-74809. they also list the Motorcraft one http://www.summitracing.com/parts/mof-yg350?rrec=true.

[Steve83]

delco1946 wrote

Do i put an open/closed valve in the heater hose line? Which one? both?

The 4-way valve in both lines is best, for several reasons.



But there are many others available.

delco1946 wrote

do i have create a system to allow continuous flow through the hoses for the engines health (but effectively allow the heater to be cut off?

That's what the 4-way does, because modern vehicles require flow through that circuit any time the engine is running, for several reasons.  To determine if yours requires it, just look at what's in that circuit.  If you see any sensors, then they can only work when coolant is flowing past them.

delco1946 wrote

What valves will hold up to the fluid corrosively, pressure, and hot temperature?

Any of the dozens of valves made for that purpose.

delco1946 wrote

Finally, is it possible to add actual ac in the future?

Of course.  There are many options, including several configurations that Ford offered from '80-96.

jstone4646 wrote

...use a joining connector to just completely bypass it.

It's easier to just disconnect opposite ends of the hoses, and then connect one of them back to the open nipple on the engine.

delco1946 wrote

...id have to drain the coolant each time right?

No, you'd barely lose any coolant each time, once you practiced your technique a few times.

jstone4646 wrote

...you would not want to leave stagnant coolant in the heater core all summer long...

Stagnant or flowing is irrelevant - coolant ages at exactly the same rate no matter what (when it's in contact with metal - not in the plastic bottles).

delco1946 wrote

If i drained it, could its guts rust?

No, for several reasons - primarily because only Iron/steel "rusts", and the heater core is brass (Copper/Zinc alloy).   It would only corrode (VERY slowly) if you left it open to the elements for years.  If you connect that 2nd hose back to the heater core, it won't corrode (internally) fast enough to detect at all; whether full of coolant, or dry.

Gary Lewis wrote

And all of the engines have a bypass system in the cooling system...

I'm not sure what you mean, or what you're saying gets bypassed.  But simply blocking the heater loop on a 300ci/4.9L will cause problems because the coolant will have nowhere to flow when the t'stat is closed.

Gary Lewis wrote

...you can just put a valve in one of the heater hoses, and it doesn't matter which one.

It's always better to put it on the high-pressure side; putting it on the return side will cause high pressure inside the heater core, which will lead to leaks.

[delco1946]

So i think this is the same kind of valve linked to before. I don't think i can use this - its vacuum operated and from what i can tell connects to your dash ac controls - which i do not have. I was hoping someone knew of a mechanically actuated valve to be simple. e.g. i pop the hood and turn a knob or two.

And I know AC can be added  Anything is possible. I was hoping to get an idea of what level of effort is required. Can i just switch out some parts or is it going to be major headache?

[Steve83]

delco1946 wrote

...its vacuum operated and from what i can tell connects to your dash ac controls - which i do not have. I was hoping someone knew of a mechanically actuated valve to be simple. e.g. i pop the hood and turn a knob or two.

Why wouldn't you have the knob in the cab, so you don't have to open the hood?

Vacuum IS mechanical.  But if you don't want to run a vacuum line (which is pretty simple, cheap, effective, & reliable when done properly), you can simply cut/break the vacuum motor off that valve, and hook a cable to it.

Or a knob if you like opening the hood.

delco1946 wrote

...what level of effort is required. Can i just switch out some parts or is it going to be major headache?

IDK how to answer that - it depends on how you define your levels, and whether you consider switching some parts to be a major headache.  But I don't know what tools you own & know how to use, or how much work area you have available, or what experience you have.  Parts DO have to be added & or switched - yes.  None of them require heavy lifting or advanced skills.  You might also have to cut some thin sheet metal - I can't say for sure because I don't know exactly how your truck is built, or what condition it's in right now.  If you get a complete working sealed refrigerant system from a newer donor truck, you don't even have to pay a pro for evac & recharge.

I've swapped a whole A/C system on an F150 in my driveway in ~1 hr using cordless tools.  Read this caption, and follow the links in it for more info & pics:

[Frank Wyatt]

I was hoping Steve would comment on this. And I agree, why wouldn't you use the vacuum controlled bypass valve? It's easy to install in your your heater hoses and with the electric vacuum switch and a toggle switch, you'll be able to operate it from inside your truck. The vacuum switch isn't necessary but it's a way to have in cab control of the bypass valve if your truck does not have factory air like my truck. That's the way I'm going when I fix my heater. I was going to use manual shut-off valves until I learned from Steve about that super nice heater bypass valve used on the Ford Explorer and likely other top of the line vehicles. I think it's a super slick solution and will look more well thought out as opposed to looking jerry rigged together.

[Gary Lewis]

Steve83 wrote

I'm not sure what you mean, or what you're saying gets bypassed. But simply blocking the heater loop on a 300ci/4.9L will cause problems because the coolant will have nowhere to flow when the t'stat is closed.

Good point. I'd forgotten that the 300 doesn't have a bypass in the cooling system as the V8's do. And it would certainly cause a problem to prevent the coolant from circulating in the block prior to the thermostat opening. Thanks for correcting me.

But, on a V8 you can put a valve in one of the hoses as they do have a bypass that will still circulate coolant when the 'stat is closed. In fact, that's why the bypass is there.

Steve83 wrote

It's always better to put it on the high-pressure side; putting it on the return side will cause high pressure inside the heater core, which will lead to leaks.

However, I disagree on this. The pressure in the system is the pressure in the system since the cooling system is a closed, pressurized system

[Gary Lewis]

I agree.  But there's a possible upgrade: If you have a single tank get the correct HVAC control for a dual tank and use the tank switch to control the vacuum valve.  What better place to have a switch that controls part of the Heating Ventilation & Air Conditioning system than in the Heating Ventilation & Air Conditioning control panel?  

(I've always thought Ford's placement of the tank switch questionable.)

[delco1946]

Well I guess I can’t disagree with that logic, But I am very unfamiliar with doing this sort of work so I would need some pretty detailed instructions on how to wire a switch through the firewall, where to mount it, and the actual products needed them selves much like was done with the vacuum four way switch. For example I am not clear if a switch mounted in the cab has a vacuum line going all the way to the switch or if the vacuum hose terminates somewhere in the engine bay where the signal is transferred into an electrical signal and Carried into the Cab via a wire.still learning hear....

[grumpin]

I read that the valves can leak, and noticed mine is seeping. Just ordered this improved valve.

https://www.amazon.com/gp/product/B07GT22JTC/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1&pldnSite=1

I have this switch, never installed it as I have A/C and when I go to Max A/C the valve bypasses. Plumbed into the same line that closes the Max A/C door.

https://www.summitracing.com/parts/vta-11542-vus

Edit: Corrected link.

[Steve83]

white knite wrote

...use the vacuum controlled bypass valve? It's easy to install in your your heater hoses and with the electric vacuum switch and a toggle switch...

Why use an electric switch to control a vacuum valve to control a vacuum motor?  It's simpler to use a vacuum valve, which was standard equipment on '87-early '88 F-series & Broncos; and it would probably fit where the tank/rear window switch goes on a bullnose A/C control.



The top Left slide is the blower speed switch; the top center button is the compressor clutch switch & indicator; the bottom Left slide is the recirculate vacuum valve (the target of this pic being in this discussion); the other 2 control the temperature & diverter door cables.  You'd just remove that valve from that panel, mount it to the bullnose panel, and install a matching knob.  Changing the label on the panel would be difficult to make look right, but doable.

Gary Lewis wrote

The pressure in the system is the pressure in the system since the cooling system is a closed, pressurized system

That would be true if there was no circulation, like in a tank.  But since there's a pump forcing the fluid to move, there MUST be suction (lower pressure) on the inlet side of the pump, and higher pressure on the outlet - otherwise, the fluid wouldn't move (Newton's 1st & 2nd laws).

Note service procedure #1 in the first TSB in this caption:

delco1946 wrote

...a switch mounted in the cab has a vacuum line going all the way to the switch...

That wouldn't be a switch; it would be a manual vacuum valve, as shown above.

delco1946 wrote

...or if the vacuum hose terminates somewhere in the engine bay where the signal is transferred into an electrical signal and Carried into the Cab via a wire.

Yes, that's what white knight described, but it's unnecessarily (IMO) complicated.

This shows how the '80-86 & late-'87-96/7 HVAC vacuum system is built:



For each vacuum motor diaphragm (one of the motors has 2 diaphragms), there's a corresponding section of the mechanical valve in the control panel.  You'd just add another mechanical valve to control the vacuum motor on the heater hose valve.

[grumpin]

Steve83 wrote

white knite wrote

...use the vacuum controlled bypass valve? It's easy to install in your your heater hoses and with the electric vacuum switch and a toggle switch...

Why use an electric switch to control a vacuum valve to control a vacuum motor?  It's simpler to use a vacuum switch, which was standard equipment on '87-early '88 F-series & Broncos; and it would probably fit where the tank/rear window switch goes on a bullnose A/C control.

To me it's easier. Wire in a switch and use it when I want to. Do you mean to get this vacuum switch and install it where convenient?

Edit: Add question.

[Frank Wyatt]

That's my plan when I fix my heater Grumpin. Steve, that would eliminate the need for the toggle switch and electric vacuum switch, but the OP, IIRC, and my truck does not have the HVAC vacuum control panel, they are heat only, no factory air or the accompanying bits and pieces. My truck has two cables, one for the underhood blend door and the other switches from defrost to floor heat.

[Steve83]

white knite wrote

...my truck does not have the HVAC vacuum control panel, they are heat only, no factory air or the accompanying bits and pieces.

That vacuum control valve could be mounted almost anywhere - maybe where the factory fog light switch goes, or just to the bottom lip of the dash.  If you're good with a dremel, you could put it into your heat-only control panel.