Thought I'd get some opinions on this before I go ahead and buy stuff, or mess with anything.

So to keep my heater core from bringing heat into the cabin when it's over 100° outside I've been contemplating putting in a valve to block off the heater core. I've seen where people have put valve in the heater hose to block it off, but I'm not happy with having to go under the hood and turn the valve.

What I've schemed up is getting a vacuum actuated valve that will close when a vacuum is applied to it. Based on the vacuum diagrams in the FSM I could tap into the dark green vacuum line (opens recirculation door) and connect it to the valve, so when the a/c is placed on max it will block off hot water from the heater core.

I've found what seems to be a valve intended for this exact purpose that I think will work. It's a http://www.ebay.com/itm/Four-Seasons-74857-HVAC-Heater-Control-Valve-VACUUM-CLOSES-5-8-X-5-8-/390569679970?pt=Motors_Car_Truck_Parts_Accessories&hash=item5aefc45c62&vxp=mtr. Then I'll just need some vacuum lines and a t connector to tap into the recirculation door line.

Here's the vacuum diagram from the FSM:

 

I like the idea. Alot of work but may well be worth it if you get it done before august really starts in.

 

Ok, so I think I'm going to end up using a instead because it not only blocks off the heater core, it also bypasses it. It's the same price too. The only difference is it is open when it gets a vacuum instead of closed when it has a vacuum, but I can just hook it to the light green vaccum tube (recircuation door close) instead and it will serve the same function since the recirculation door is only open when on max a/c or the system is off.

 

Make sure to take lots of pics and let us know how it works out. I am interested it this. When i first got my truck a few years ago i did the ball valve in the line but, when i replaced the hoses over the winter i never got around to re installing the ball valve. Cars back in the 80's and prior used to come with this standard... Mack trucks had done it since the 60's.


BTW, that is a FORD valve.... and Autozone stocks them in store.

 

I don't think this will be to difficult of a job. I think I can just put a t in the vacuum line going to to recirculation for actuator, then run a line through the firewall.

 

I like this idea. Which is the inlet to the heater core. Is it on the driver side of the engine or the passenger side. I assume one wants this valve on the inlet to the heater. as said above take lots of pictures because I would like to know where that vacuum hose for the recirculation door is.

 

Ok, got this done the other day. This valve does in fact block off the heater core when it gets a vacuum, not the other way around. The description is just weirdly worded. Anyway everything was pretty straight forward. The only issue I ran into was the heater hoses not wanting to come off the heater core, so I had to slit them to split them off, and then trim them back further some. I haven't had a chance to see if it makes a difference with the a/c or not yet, but it certainly does block off the heater core.

Here's the valve and the tee connector I bought at autozone. The vacuum hose I bought was 7/64" because they didn't have 1/8" and the tee was meant for 1/8" (aka 8/64", so barely a difference).




This is the dark green hose that I got the vacuum from. It's right there in the passenger's side footwell next to the kick panel. I just pulled it off, put the rubber elbow onto the tee, and then put another piece of hose from the tee back to the actuator.




I ran the hose along the transmission hump and out of a grommet in the firewall where the shifter cable goes through.






And here's the valve installed in the engine bay.




And here's a diagram of the cooling system in case anyone is interested.

 

Nice Job!

I think I may have to foolow your lead. I have had issues with the blend door in the past where it just switches to defrost mode and stays there. It makes me wonder if the door is not closing properly. That dash was had been taken apart once to replace the evaporator so who knows if it was put together correctly.

 

The blend door (cable operated) only controls the temperature, the diverter doors (vacuum operated) direct the airflow to various vents. The default setting with no vacuum is defrost, so I'd imagine you have a vacuum leak somewhere.