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No Heater Control Valve '93 see photo

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Old 09-06-2012, 05:23 PM   #1
bruce119
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No Heater Control Valve '93 see photo

OK seems that some have a heater control valve some don’t I have a 93X. From what I found it should be located near the firewall as the hoses enter the heater core. As you can see from the photo there is nothing it is a straight hose from the core to the block and pump.

Now the reason for concern, I just rebuilt and converted the A.C. to R134 replaced everything but evaporator and condenser. The air blows kind of cold just a little better than it did. With the control on Max A/C and the fan on high (#4 position) it blows kind of cold BUT as I drop down to #3 fan speed it blows a good 10 deg. colder even more as I drop the fan down to low (1) and 2.

Now my thought if there is no heater control valve my thinking tell me the heater core is flowing with hot water and hindering the A/C.

I am thinking of putting a manual shut off valve on the heater hose to bypass the heater core. I am in Florida after all and don’t use heat much. It wouldn’t be that bad to open and close a valve say in the Fall & Spring.

How about some of you guys chime in with ideas, thoughts and/or suggestions.





Thanks
Bruce from Florida




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Old 09-06-2012, 07:13 PM   #2
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if there's no heater control valve, then there must be a door separating the heater core and evaporator inside the heater box, no?

i think the reason it blows colder at lower fan speeds is that you're giving the air flowing through the evaporator longer to get cold. it should also be noted that R134a refrigerant is designed to work at a different pressure than R12 (higher pressure required for R134 as i recall). this means that when you convert an R12 system to R134a it won't get quite as cold. did you install a R134a rated compressor and pressure switches?

one last thought, how are you measuring how much refrigerant you've put in? outside temp effects how much pressure you should have. oh, and did you use a vac pump on the system before putting refrig in?
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Old 09-06-2012, 07:31 PM   #3
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if there's no heater control valve, then there must be a door separating the heater core and evaporator inside the heater box, no?

i think the reason it blows colder at lower fan speeds is that you're giving the air flowing through the evaporator longer to get cold. it should also be noted that R134a refrigerant is designed to work at a different pressure than R12 (higher pressure required for R134 as i recall). this means that when you convert an R12 system to R134a it won't get quite as cold. did you install a R134a rated compressor and pressure switches?

one last thought, how are you measuring how much refrigerant you've put in? outside temp effects how much pressure you should have. oh, and did you use a vac pump on the system before putting refrig in?
I replaced everything hoses, compressor, dryer, orphas tube, the only thing I didn't do was evaporator and condenser and I flushed the heck out of them. I had an A/C shop do the recharge. I made sure they put a good long vacuum on it and they said all the pressures looked good.

So not sure how the blower isolates the hot from the cold. The best I can tell is there mite be a door in the blower box. Maybe it's not closing all the way. Don't know and don't sound like it would be an easy thing to check. That's why I'm thing of a manual bypass.
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Old 09-06-2012, 07:50 PM   #4
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1994 is when they added the heater control bypass valve. Without it you will get hot water into the heater box and NO you cannot just block off the line.

On the 4.0 OHV you need to let the water get from the intake to the water pump. If you just block off the line you won't be getting the bypass you want. I've seen some people just loop the hoses together which is fine, except you won't have heat.

This is the thread you want to read about installing the heater control bypass valve. Its easy to do, and helps.

http://www.explorerforum.com/forums/...t=heater+valve

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Old 09-06-2012, 09:16 PM   #5
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1994 is when they added the heater control bypass valve. Without it you will get hot water into the heater box and NO you cannot just block off the line.

On the 4.0 OHV you need to let the water get from the intake to the water pump. If you just block off the line you won't be getting the bypass you want. I've seen some people just loop the hoses together which is fine, except you won't have heat.

This is the thread you want to read about installing the heater control bypass valve. Its easy to do, and helps.

http://www.explorerforum.com/forums/...t=heater+valve

~Mark
I saw that post. How about this below is a rough drawing. I understand you can't just can't close it off. But with two Ts and two shut off valves I would think I would be able to make a simple manual bypass. With the intake closed and the middle (in-between) open it would loop no hot water into the core. And with the middle (in-between) closed and intake open the heat would function normal. I realize I would have to lift the hood to make the switch but it would be seasonal Spring and Summer. Seems pretty simple to me see any problems with this.
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Old 09-06-2012, 09:24 PM   #6
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As long as you never have both valves closed at the same time, that will work..

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Old 09-06-2012, 09:32 PM   #7
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if you want to just try keeping the hot water out of the heater core w/out stopping the water flow, you can buy a plastic hose splice from any autoparts store (they come in a variety of sizes and combinations) and just attach the 2 hoses together. shouldn't cost you more than $2 to find out if this is the problem and by connecting the 2 hoses together you won't stop the flow. if this solves the problem you can try adding a valve (as per your diagram) later. tip: mark the hoses before you disconnect them

from looking at your "temp" control, it looks like its cable operated. if so, can you follow the cable to the heater box and make sure the door is closing all the way. the blower doesn't isolate hot/cold. it's the "temp" control slide and "max a/c" is "recirculate" = no fresh air.
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Old 09-06-2012, 09:35 PM   #8
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Your temp setting controls a blend door that either sends some or all of the air flow through your heater core. It should be able to completely isolate your air flow from the heat. It`s been a while since I`ve been digging around in the guts of my 93 heater/AC system, but I am certain I was able to see the blend door either from removing the fan cover under the hood, or possibly even removing the heater core cover under the dash. I would check to see that it is closing all the way, and that the sealing surface is intact. When my AC worked (sprung a leak a couple years ago, and I haven't got it fixed) it worked fine, especially after I switched to the new coolant and recharged it. I am skeptical on the need to bypass the heater core, EXCEPT to mickey mouse a solution to an existing problem... Or to help get cooler air flow thru a non-AC system.




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Old 09-06-2012, 09:37 PM   #9
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As long as you never have both valves closed at the same time, that will work..

~Mark
I will post photos when I do it. Will make some sort of label/diagram and attach to the area making it clear what positions the valves should be in for heat and bypass no heat. I will be the only owner I run my vehicles till you can't get anymore and they wind up in the junk yard.
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Old 09-06-2012, 09:38 PM   #10
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Over the years, the doors don't seal near as well. Our poor '92 a/c gets about 10F cooler when I have the heater control bypass valve in.

Its actually a common mod.. Especially since Ford started using it in 1994 and they didn't change the heater/ac box between 1993 and 1994.

~Mark




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Old 09-06-2012, 09:45 PM   #11
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Your temp setting controls a blend door that either sends some or all of the air flow through your heater core. It should be able to completely isolate your air flow from the heat. It`s been a while since I`ve been digging around in the guts of my 93 heater/AC system, but I am certain I was able to see the blend door either from removing the fan cover under the hood, or possibly even removing the heater core cover under the dash. I would check to see that it is closing all the way, and that the sealing surface is intact. When my AC worked (sprung a leak a couple years ago, and I haven't got it fixed) it worked fine, especially after I switched to the new coolant and recharged it. I am skeptical on the need to bypass the heater core, EXCEPT to mickey mouse a solution to an existing problem... Or to help get cooler air flow thru a non-AC system.
Well before I do my mod. I will just loop the hoses and see if it really makes a difference. Now I see you are in Canada and little cooler there heat would be more important to you. Here in Florida 90 plus 80% of the year I mite use heat just a couple times a year. Micky mouse yea but seems like a simple quick cheap fix for now.
.




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Old 09-07-2012, 07:53 AM   #12
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Being in hot humid FL I just took the 2 hoses & used a hose coupler & by passed the heater core totally. I don't need heat where I live.
My 94's had the valve & I still did the same thing.




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Old 09-07-2012, 08:11 AM   #13
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Being in hot humid FL I just took the 2 hoses & used a hose coupler & by passed the heater core totally. I don't need heat where I live.
My 94's had the valve & I still did the same thing.
I don't think I want to eliminate the heater core altogether. And I will fix it proper when I have time.

Also my concern would be if the core is cut off completely for a long period of time say a few years. Wouldn't that stagnate water in the core possibly cause corrosion and if you need your heat hooked back up could be trouble.
Just a thought.

Thanks all I think the quick and easy is to just do a quick bypass and test to see if there is a difference. If there is than I know latter on I need to dig into those doors in the blower box. That doesn't sound like a fun job though.

More updates to come.
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Old 09-07-2012, 12:33 PM   #14
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Buy and install a '94 heater control valve. Remove the vacuum actuator. Zip tie the arm in the open/ closed position depending on the season. You shouldnt be into it for much more then $25 with the valve and clamps.




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Old 09-08-2012, 10:31 AM   #15
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Buy and install a '94 heater control valve. Remove the vacuum actuator. Zip tie the arm in the open/ closed position depending on the season. You shouldnt be into it for much more then $25 with the valve and clamps.
you can probably just get a small ball valve for less. when the handle is in-line with the hose it's open, when it's not in-line with the hose it's closed.




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Old 09-08-2012, 11:21 AM   #16
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you can probably just get a small ball valve for less. when the handle is in-line with the hose it's open, when it's not in-line with the hose it's closed.
You can't just stop the coolant, it must bypass the heater core.

Quote:
Originally Posted by snoranger
Buy and install a '94 heater control valve. Remove the vacuum actuator. Zip tie the arm in the open/ closed position depending on the season. You shouldnt be into it for much more then $25 with the valve and clamps.
If your going to go that far, might as well run the vacuum line under/behind the glove box and t into the line that already gets vacuum when the a/c is set to max a/c.

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Old 09-08-2012, 01:05 PM   #17
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You can't just stop the coolant, it must bypass the heater core.



If your going to go that far, might as well run the vacuum line under/behind the glove box and t into the line that already gets vacuum when the a/c is set to max a/c.

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we are all aware that you can't just turn off the heater water flow (read previous posts). we're suggesting a valve in conjunction with the bypass depicted in the diagram




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Old 09-08-2012, 01:32 PM   #18
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we are all aware that you can't just turn off the heater water flow (read previous posts). we're suggesting a valve in conjunction with the bypass depicted in the diagram
I must be lost then. The hand drawn diagram above shows valves used as a bypass (2 valves) but then there was the much later post that just said to use a valve which implies that its something different than was already posted.. So, I took it as using just "a ball valve" as the suggested solution.

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Old 09-08-2012, 05:11 PM   #19
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I also have a 93 that did not have the control valve. I did add one to my truck and I can say it helps not a ton but every little bit helps when your talking out side temps of over 100 or better!

I ran the vac line from the pot that controls the max AC shut off to the valve so that the hot water flow is by passing the heater core when off and at Max AC. now the valve dose leak a bit as in some flow gets past it to the heater core but not much. Like Maniak I have seen at lest a 10 deg drop also.
Just remember that the defrost system also uses both heat and the AC. the AC when defrosting is for helping to dry the glass as with out it defrosting takes a lot longer and in fact can become worse.

Also over time the control cables sometimes can shift leaving the blend door not fully closing. you can drop the glove box and see the top of the air box and even adjust the cables there or tighten there holders if need be. I had to do that also as my had slipped and were holding the door part way open. As for the sealing ability of the door well wish I knew how to get to that and fix it easily as I am sure mine is gone but the way it is now is way better then it was. Still not like when I bought the truck at 60,000 miles but that was over 165,000 miles ago now and things do age after all it is now almost 20 years old. Plus R12 was way better then R132 is so just converting it you lose some efficiency.




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Old 09-09-2012, 10:22 PM   #20
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The valve is $30 at autozone or napa. Ask for one from a 94+. To install it you only need a T fitting for the vac line under the dash on the right side. Feed a vac line from the T to the new valve. done. No need to open your hood to get the heat. It will look stock, and you will probably have spent less time and money than if you try and piece together several valves and hoses.

Just use the Ford part.




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