So I know that there has been threads on this mod several times in the past years, but when I went to do a search on it I didn't find anything. So with summer approaching I thought it was worth posting again for newbies and share my method of doing this mod with pics. The reason for doing this mod is to shut off the flow to the heater core while the A/C is running thus allowing for cooler A/C . I was fortunate I saved a PDF file that Pete FTE member "F250_" ( Also known for making the infamous Pete's Cover you see in folks sigs @ TruckMods ) had done, Thanks Pete. Also want to give Neal FTE member "nlemerise" credit too for he had added much info that I used. Here is what I put together using Pete's PDF file.

I started with a '97 Ford Explorer V-6 Heater Core Bypass Valve shown above. Auto Zone P/N 74809, you can also order from Ed a Motorcraft F87Z-18495-AA valve

I Then spliced the valve into the heater hoses near the passenger side firewall, shown here.

[FONT=Calibri][SIZE=3]The heater core Bypass valve that I used is vacuum operated so I needed to splice into the A/C vacuum supply line using a vacuum "t" and 1/8 inch vacuum hose. If you push in the rubber bumpers on each end of the glove box it will swing out of the way and you can easily access all the HVAC vacuum lines just to the left. I chose to use the white hose (which is the Max A/C setting) to splice into, under the premise that when you first start your vehicle on a hot day the A/C setting is used first due to the fact that it draws outside ambient air over the evaporator which is typically cooler than the inside of your trucks cabin. Once the air in the cabin begins to cool to a level that is at or below the outside ambient air temperature you should then switch to Max A/C so the air being drawn across the evaporator is recirculated cabin air which helps the system work more efficiently. You can however splice into the red vacuum line if you want the bypass valve to work in both the A/C and Max A/C settings with only one drawback which is it prevents the A/C to work with defrost.

My results were a solid 10 degree drop through the dash vent, I was at 48 degrees before this mod, I am now at 38 degrees, I am tickled pink over this result.

My parts cost less than $25 bucks, I spend more than that to get my truck washed, and was easily installed within an hour or less. Above is a pic of all the parts I needed to do this mod:
1.) Auto Zone P/N 74809 Heater Core Bypass Valve for a 97 Ford Explorer V-6
2.) Five feet of 1/8 inch vacuum hose
3.) Four 7/8" thru 1" screw hose clamps
4.) 1/8" vacuum "T" fitting
for additional information you can try The" Roadside Help Network" list of mods and "GUZZLES" mod page. Thanks to all members that helped make this mod possible for me.

 

added to my to do list. great walkthrough too. you da man.

 

I love this mod, being in hot/humid central TX. I'm sure it works the same both ways, but I remember there being arrows on the valve for flow direction. Wouldn't the one in that pic be upside down? My vac canister is up. Also, I tied into the white line where it connects to the cannister at pass. floorboard. I guess that's the blend door maybe.? Put 1 1/2" piece of vac line on the nipple, plugged T into that, plugged white line and line going to ranger valve into T. Little shorter route and I didn't want to cut the white line. I'm really no good at this stuff or I'd put up some pics. I've also noticed out of the 2 ranger valves I've used, they both leached a little coolant by making the lines to the heater core quite warm. In my case it's certainly worked better than nothing, though a valve that shuts completely off would be better. I do like the ranger valve setup, maybe I just got unlucky with the two I've purchased.

 

Another detailed DIY mod with pics, priceless, nice job and glad its working for yaa..reps sent.

 

There were no arrows on my valve, I based the poisitioning on a pic Neal posted, you could be right. I will have to double check that, thanks for pointing it out. As far as the ranger valves leaching, its too early for me to tell yet, But I wish I would've ordered a Factory Ford part from Ed, because I never have good luck with AZ parts. But, I wanted to get this done today because its hot temps here on out in Vegas, from today on through the rest of summer and into next fall.

 

You've got an awfully good point about getting the factory ford parts. I got both from Autozone. That prob. tells you something right there. Maybe I should contact Ed and go for the "full effect"!

 

38 degrees? Wow that is cold! Probably too cold for my blood. Feels like I can hang meat in my cab with the A/C on max, I can't imagine what it would be like if it were any colder. I'd probably need to wear a coat even during the summer.

 

reps sent, nice job documenting this mod!

 

its 38* just stepping out my front door right now,,lol nice job Dan..both work and write up...

 

I keep intending to do this mod. Thanks for the reminder. I'm gonna use the red vacuum line because I probably don't use the defroster more than 6 times a year but there are LOTS of times when the ambient temp is OK but I have to run the A/C because the damned vent setting blows friggin' HOT AIR even with the temp on it's coldest setting. Anyway, nice writeup.

 

Thanks Kent,
It's quick, easy and cheap. On the defrost, I've heard that one reason the A/C runs with the defrost mode is to keep the seals in the system oiled for longevity when the A/C hasn't been used in months, could just be an Old Wives Tale though, Im not sure.

 

I had always heard that it was to dehumidify the air being used to defog the windshield. Hmmm......... Either way, I guess its true.

 

The reason the A/C compressor and system work in defrost is so that the air moisture content goes down. As the temperature of air drops, the moisture holding capacity goes down, and allows condensation to occur if the moisture content were to stay constant. Cooler air cannot hold the same amount of water vapor that warm air can. Think of a cold ice filled drink or beer on a hot day. The air surrounding the container has moisture drop out, on the container walls. The a/c is used to keep the air dryer as moisture is kept down. A lot of the Ford compressors or rather computer systems have an anti slugging strategy built in so that if the compressor is kept off for long periods of time, especially when parked, it willl be commanded on automatically and in a pulsed manner in order to prevent damage from liquid accumulation. If you hear a gas motor Ford start after being parked or not having the A/c compressor used for an extended period, you will hear a loud ratcheting noise. That is the anti slug strategy built in doing its thing. Almost sounds like it is going to grenade, but it doesn't haha.

 

Sheldon Plankton beat me to it...

 

I keep thinking that I want to do this mod, but I would rather have a switch in the cab to control the flow so that I could turn it on and off at will, rather than just when the selector was in certain positions. I've been trying to come up with a solution, but have not found anything at this time.