How to install a heater core bypass valve

[sly]

Parts needed:
Dorman part # 74809
1/8 vacuum line
1/8 vacuum T
ultra-black or a body grommet with a 1/4 pass through for the vacuum line

Might need:
3/4 heater hose in case you cut something wrong like I did.

Tools:
utility knife to cut hoses
5/16 driver (who uses a flat screwdriver on hose clamps?)
5/16 drill bit (if not using a grommet - if using a grommet, get the right size drill for the size hole the grommet fits.)
handheld drill

There is no actual modification to the vehicle itself except for the hole to be drilled to pass the vacuum line through the firewall unless you know of another place to poke through that doesn't modify the firewall.

First cut the heater hoses about an inch past the angled edge they hang over and attache the bypass valve in-line at that point.
Here's a pic of it installed... not leaking, and in heating position (any position from HI-LO to DEF on the sliders)


Here's a pic in the AC position (VENT to PANEL) in bypass mode:


I drilled the hole above where the vacuum line for the brake release comes in:


and ran that over to the valve as you can see in the images of the valve.
Pull the BLUE vacuum line (may be black with blue stripe on older boxes) and install the T there with a little section of vacuum line and then attach the end of the vacuum line from the firewall to it.


Now the heater core will be completely bypassed in VENT and PANEL/MAX.

How the valve works:

[Ike Clanton]

Cool mod!

[kishy]

Awesome mod.

Also, a thought. If the line is still in good condition and you've disconnected your automatic parking brake release, you could re-use that vacuum line with a little re-routing, if only to get the vacuum through the firewall.

[gadget73]

What does that under-dash vacuum motor operate? Is that the one for the panel air door ?


I like the idea. Should help with AC performance for those of us who have imperfect seals on our blend doors, which is basically everybody now.


My concern when you mentioned something about a shutoff valve elsewhere was the ECT not having any flow, but this neatly fixes that issue. Whats this originally from, a Ranger I think you said ?

[sly]

Yeah, 96 Ranger.
Yes, full panel actuator is where the T is.

[86VickyLX]

Has anyone tried this with an 86? With the dual heater pipe?

[sly]

might have to create a loop with excess hose to get from the end of the pipe to the valve.

[86VickyLX]

that seems like it wouldn't look neat. I'll see what happens when I put the cobra lower on, since I'll have the upper intake off, I can see what will happen when I try to install it.

[sly]

make the loop go down against the plenum and come back up to the valve. good way to hide it that way.