Vacuum Controlled Heater Core Valve

Gary Lewis wrote

Yup, I have A/C.  But, when it is in the 60's outside I don't see the need to run it.  However, with coolant to the heater core the air temp is way too warm on Vent.  As for needing warm air then, just move the lever to Heat.  

I think you just answered your own question, Chief!

If the air temperature is too warm on VENT because of the hot coolant in the heater core, why not turn on the A/C?  

Doesn't that qualify as a need to run it?  

Nope.  I don't like to run the A/C when it isn't needed.  And, when the outside temps are in the 60's it should not be needed.  But, because Ford didn't spend the money to put a valve on our trucks, like they did other vehicles, then we have to turn the A/C on when it isn't needed.  I'm just fixing what Ford was too cheap to do right in the first place.  

Gary Lewis wrote

Nope.  I don't like to run the A/C when it isn't needed.  And, when the outside temps are in the 60's it should not be needed.  But, because Ford didn't spend the money to put a valve on our trucks, like they did other vehicles, then we have to turn the A/C on when it isn't needed.  I'm just fixing what Ford was too cheap to do right in the first place.  

Ford and every other manufacturer *wants* you to use A/C more often.

If you use it more often, the A/C system is less likely to leak and give you less problems.  The old "use it or lose it" expression applies here.

That is why the A/C mode is never at the end of the climate control selections on the control panels.  If you notice, it is always at the beginning - you have to go past it in order to get to heat.

Apparently there were engineers that didn't understand that.  Otherwise, why would there be so many applications for valves to turn off the water to the heater core?  You can go back through this thread and see the many that others have posted.

Anyway, I've already made the mod and plan to put it on Dad's truck when the time comes - and enjoy nice cool air when in Vent.  

Gary Lewis wrote

Apparently there were engineers that didn't understand that.  Otherwise, why would there be so many applications for valves to turn off the water to the heater core?  You can go back through this thread and see the many that others have posted.

I suppose so the MAX A/C mode will be even cooler?  

If the MAX A/C isn't cool enough, there is nothing else you can do.  So that valve helps, if you live in a hot area.  I live in the South, which is why I put one in Lucille.

Where there ANY applications that had a valve that blocked the coolant flow when the VENT mode was selected?  

Okay, I apologize that these pictures are not the very best since I was photographing inside the dash, but they should suffice to explain the differences:

1980-1982, early style vacuum switch and cable attaches by looping around a post on the lever arm and is secured by a screw in tab (red)


1983 only... both the cable and controller are unique to this model year. The vacuum switch is the newer style and has the newer face cosmetics. But the lever is offset and has a post similar to the 80-82 system. The cable end loops around the post but the sheath is secured by a square plastic block that snaps into the controller body (black)


1984-1986, late style vacuum switch and a completely flat lever with a small hole in it instead of the post. The cable sheath is secured by a a round (black) cable end that snaps into the controller body. The cable end engages with the lever by dog legging through the small hole. (Same picture already shared but repeated for completeness)


I pulled one of the new style cables for Dave, and I can post up a picture if the bare cable ends, but I didn't photograph that in the junkyard. I wanted to extract a 1983 cable for photographic purposes, but I had limited time and it takes quite a while to get one of those cables out in one piece! Hopefully the en situ shots get the idea across. Basically if you have a 1983 controller you need the 1983 cable for it. The lever/cable system is unique and not compatible with other years.

Jonathan - Those are very good pics.  Thanks!  So, there are indeed three different cables: 1980 - 82; 1983; & 1984 - 86.  I'm going to guess that they had some problems with the 1983 cable or it wouldn't have been replaced so quickly.

Three different cables and three different controllers. Note in the three pics the differences in the white plastic controller body and the three different styles of levers. Here is a pic of the 84-86 style cable ends:

Cool!

If, some day when you have nothing better to do, you were to pull one of the 1983 controllers out and get pics of it and the cable ends we'd have a complete set.  But, just when you have nothing better to do, and I know that's not any time soon.

Gary I will certainly do that. On this trip I had a strict time limit. The main purpose was to cash out the transfer case core charge and grab a late style cable for Dave. On a more leisurely trip I will document the 1983 cable

Gary Lewis wrote

The problem we have is that we would like the valve to work in both Vent and Max A/C. Unfortunately our control doesn’t give a vacuum signal for both of those situations and not others, as shown by a table from the 1981 shop manual, below.

My plan is to use connection #1 on the HVAC control, which isn't used. As shown below it provides vacuum on both Vent and Max, but not on Norm. The plastic on the control isn't drilled, and there's no hose on that port of the connector, but I think that should be easy to fix  However, that is for a 1980/84 control, and I haven’t looked at a 1985/86 control to see if that is possible with them.

I hate to bring this up being so old but it is time to do this to my truck and have a question.
First I could not find this in Documentation did it get left out? Maybe in the "up grade: area?

If I under stand the control using the #1 port we have the water shut off in AC max & vent, is this true?
What would happen if we tee'd into port #3? We then also have the water off in normal would this be a issue?
I am also thinking if the water was off in any of the control settings moving the temp control would do nothing right?
Dave ----

No problem bringing it up.  If you tap into #3 then you won't have any temp control.  And, as you said, the temp lever would do nothing.

And it is in Documentation/HVAC/HVAC Systems and on the Heat Shut-Off tab.  Is there a better place?

Gary Lewis wrote

No problem bringing it up.  If you tap into #3 then you won't have any temp control.  And, as you said, the temp lever would do nothing.

And it is in Documentation/HVAC/HVAC Systems and on the Heat Shut-Off tab.  Is there a better place?

I must not have looked that good sorry.
That is a good place as any I guess. I just need to open my eyes is all.

I do have a add on for the vacuum valve part number.
You list a 2 port valve and that would be good for 99% of the trucks but I am that 1% it does not.
Because I have a 300 six and running EFI exh. manifolds I need to heat the intake manifold so a 4 port valve that bypasses the heater core but keeps the hot water flowing is what I need.
The valves below will do this.

PN: 74809 Four Seasons
or
NAPA PN: BK6601294

I hope to pick one up ASAP as the vents are blowing hot air and don't need AC that is not working yet.

Thanks again
Dave ----

I added that valve to that page.  Thanks!

Your the man
Dave ----

My truck is a 1981 but has a 1985 complete factory A/C system in it. I had considered doing this but haven't as of yet. My plan was to get a vacuum to close valve and to tee into the black/white vacuum line on the outside recirculate door vacuum motor which is already right there where you would need it to feed the heater valve. It would only shut off the water in the Off and Max A/C mode only. But as Gary mentioned he wants it shut off in the vent mode also so not good for that. Myself I did not want it shut off in the vent mode as I use mine a good bit when it is cold out to blow heat through the panel vents so was not wanting to keep the hot water out for that reason on vent. Here is a link to some of the vacuum to close valves I was considering.

https://www.4s.com/en/ecatalog?part=Vacuum%20Closes%20Non-Bypass%20Heater%20Valve&type=p

On my 1995 Ranger this is how the heater core valve is used... only closes when the system is off or when Max AC is on, just like the recirculate door. Pretty sure they are on the same vacuum circuit.

The heater hoses are the same size too... so such a valve would be a direct fit (when closed, it allows the coolant to circulate, so one always has coolant flow). They do tend to blow up and leak if the rad cap doesn't properly regulate the pressure though (they're plastic).

81f100custom wrote

My truck is a 1981 but has a 1985 complete factory A/C system in it. I had considered doing this but haven't as of yet. My plan was to get a vacuum to close valve and to tee into the black/white vacuum line on the outside recirculate door vacuum motor which is already right there where you would need it to feed the heater valve. It would only shut off the water in the Off and Max A/C mode only. But as Gary mentioned he wants it shut off in the vent mode also so not good for that. Myself I did not want it shut off in the vent mode as I use mine a good bit when it is cold out to blow heat through the panel vents so was not wanting to keep the hot water out for that reason on vent. Here is a link to some of the vacuum to close valves I was considering.

https://www.4s.com/en/ecatalog?part=Vacuum%20Closes%20Non-Bypass%20Heater%20Valve&type=p

Well ran into a problem like you my controls are from a newer truck and I forgot that till I pulled the dash & part of the HVAC controls apart and could not figure what port had to be hooked up.
When I check here it all turned to
But unlike you I don't want heat out the dash vents when on vent as I don't have AC installed in the truck yet and the real reason I was doing this.

So now I got to figure out what to do to make this work like the early trucks?
Is there a pin out of the ports for the later trucks like the 80-84 trucks?
I know it is posted I can swap in the early controls but it took a while to find this with a lot of help from Jonathan and it works like it should so hate to go changing it.
Dave ----

To bring this later picture to the end here of the 85-86

So it looks like if you have the 85-86 control you can only tee into the white line and supply vacuum to the valve when only in MAX AC
So guess that is what I will do as the AC is not working at this time I can use MAX AC to blow air into the cab. It is better than what I have now as hot air blow in all the time.
Thanks guys
Dave ----

I do not know if this will help, but I installed an vacuum controlled cutoff valve in the heater circuit on my son's 1984 F150. A "T" was installed in the vacuum line which feeds the servo controlling the door for allowing fresh air [near the passenger inner fender]. The heater is "on" except when the A/C is placed on "MAX COOL".