I think this is a great summary post and should be somewhere so that it is easier to find. I added my own thoughts which I more or less concluded yesterday.
https://www.sportsmobileforum.com/fo...tml#post327888
Quote:
Originally Posted by arctictraveller
Installing a shut off valve has proven to improve A/C performance for lots of us. In a fit of desperation, (it was about 105deg's in the shade and I was suffering badly) I simply clamped the hose shut and the difference in cooling was quite noticeable. As you may know, this issue is caused by the heater core being right behind the blend door, next to the plenum where the evaporator supplys cold air. If the blend door leaks even a little, hot air from the heater core mixes with cold air, raising the outlet temp.
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The Climate Control system from Ford is designed for perfection. If the A/C and the flap doors are perfect and you don't overheat the engine (and on and on) it all works adequately.
Quote:
Originally Posted by arctictraveller
Even if the blend door doesn't leak air, eventually that plenum will heat up the whole box, again raising the outlet temp, although not as much. It might also depend on how well your A/C is working. If it's a little low on refrigerant, or the condenser or evaporator is partly blocked, cutting off heated coolant will make a bigger difference.
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The problem with using the heater core as an on-demand heat source is that the energy going in is too variable based on all conditions and engine/build configurations. If they had designed the CCS with a thermostatically controlled bypass valve then all conditions of operation could have been automatically accounted for.
Quote:
Originally Posted by arctictraveller
As for a bypass valve verses a shut off valve, I have to believe Ford used a bypass valve for some reason. I had no problems for the short time I had it clamped off , but I can see how a reduced or eliminated coolant flow could cause a hot spot in the head somewhere. It might not become obvous for some time though, and a small area of excessive heat would probably not be picked up by any sensors unless they were quite close to the spot. Then again, perhaps it doesn't matter, but why did Ford use a bypass valve rather than a less expensive shutoff valve?
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I have to agree it is unknown whether a block-off will create a long-term hot spot. Even more so how that restricted flow might affect a 4.6L/5.4L vs 6.8 V10 or 7.3 diesel.
Further, I read the exchange with JWA and can not see that monitoring OBDII is sufficient visibility into the block/head temperatures to identify any localized heating/not spots even setting aside the fact that these tests were on a 5.4L vs the bigger engines.
If you bypass the flow and return it to the block, then you are maintaining the same flow patterns through the engine. If you block off that flow then you are altering that flow. It probably doesn't matter but under extreme duty (bigger engines in heavily loaded 4x4 to trailer conditions) it might matter enough to cause a problem (e.g. blow head gaskets).
I posted this yesterday. The video identified the same bypass solenoid as artic traveler., my only contribution is where to install the bypass to control both front and rear heater cores.
Using this valve you are pretty much stuck with adding a vacuum switch to control it
https://www.sportsmobileforum.com/fo...tml#post327891
HOWEVER, Scalf77 previously posted using the BLUE vacuum control line for controlling a heater core block off.
This works well with a bypass valve as well.
When you use the Sol #2 BLUE (control line) = VACUUM, then you get a bypass cutoff signal for all hot to moderate conditions including MAX AC (recirculation), NORM AC (fresh air), and VENT (fresh air).
When Sol #2 BLUE = No Vacuum then coolant flow is restored for cooler but normal operations in OFF (recirculate), FLOOR (Fresh), MIX (Fresh) and DEF (fresh).
In this configuration the only difference between VENT and FLOOR is that VENT has no heater core flow and cooler air comes out through the dash registers (top drop) while in FLOOR there is heater core flow and the hotter air exits from the floor (to rise).
Remember the blend door works in all modes and that it is intended in FLOOR mode the dial will be adjusted in the HOT range. When in VENT it will be adjusted in the COOL range (but now with no heater core flow with negligible effect).
If you find the HEAT mode getting too hot even with the blend door all the way to COOL, you can then switch to VENT (blend door will become less effective as the heater core cools off). If it gets too cold, switch back to HEAT and re-adjust the blend DOOR. To put it simply, switching between VENT and FLOOR on the dash will open and close the Flow through the heater core giving you complete control at the only time you need it.
This thing should have come from the factory this way (coolant bypass valve controlled off same BLUE control line to #2 vacuum motor.
Linear Mode
