Hi All

2010 Ford Ranger 4.0L

I noticed yesterday that when I'm driving up a mountain and have to really push the peddle to keep my speed the ac air that comes out the vent changes to the defrost.
As soon as I let off the gas it changes back to the panel vents. I am assuming this is related to manifold vacuum.

Is this normal?

Thanks

 

Normal, unless you opt for Max AC.

 

No, not normal

Your Vacuum reservoir has a leak, or one of its vacuum lines does

The vent doors, defrost, panel and floor, are operated by vacuum "motors", yes that's what they are called, lol, motors
Anyway, a steady vacuum is needed to hold the doors in place, defrost is the "no vacuum needed" setting, so the default setting if no vacuum is available

There is a "black ball", a vacuum reservoir, that is used to hold a steady vacuum regardless of intake vacuum, looks like this: https://www.ranger-forums.com/attach...0reservoir.jpg

Power brakes have similar reservoir, that's why power brake booster is so large, it holds enough vacuum for 3 "assisted" pedal presses if engine should stall while driving.

When you accelerate vacuum level in the intake drops low but because of the "black ball" holding reserve vacuum that wouldn't bother your Vent settings
But in your Ranger it does change Vents, so you don't have any "reserve" vacuum, you are running straight off intake vacuum so varies with throttle position

As seen in picture the black ball is usually located in the front of passenger side wheel well, so down low at right front of vehicle

There are two hard plastic vacuum lines in the engine bay that come out of the firewall on passenger side, they look like wires because they are hard plastic hoses
There is a GREY one that runs to the Heater hose By-pass unit, this is the easiest to find
Find it and follow it back to firewall, and you will find the BLACK hose there, coming out of firewall
The black hose runs to the Black ball, this is the vacuum source hose for the cab vent motors
Follow this hose, its not uncommon for it to melt or crack near exhaust, easily repaired with correct size rubber hose splice
If black hose is OK all the way to black ball then you will need to swap out black ball, its cracked or has a bad internal check valve

All Ford vehicles use a vacuum reservoir, so not hard to find them at wrecking yards
There is an IN and OUT port so keep hoses in order
IN comes from engine/intake
OUT goes to cab

 

Hi RonD

While doing the O2 Sensor I did remove the inner Plastic fender. I did unbolt the reservoir. It's bolted to the plastic wheel housing.
When I bought the truck (2 months ago) the 2 bolts that hold the front part of the Plastic wheel housing were missing and the
Vacuum Reservoir was taking a beating as the plastic was bouncing all over the place. I knew it was a vacuum Reservoir but I
didn't know what for. Now I do.

I will do the check on the lines to see if they are broke.

Thank you!
Your knowledge on the ranger amazing.

 

Good stuff

Thank you

 

Hi RonD

You mentioned that the Vacuum ball had an internal check valve. I did find a Check Valve between the manifold and the ball. It does seem to be sticking.
Does this mean there is 2 Check valves

Thanks

 

Your year may not have internal check valve on the ball
But having an external check valve won't hurt anything if it did, as long as it is in correct direction

Ford would often add EGR valve vacuum to the Reservoir system, but instead of tapping vacuum hose after reservoir they would just add external check valve and tap the vacuum between intake and reservoir to have shorter vacuum lines
Automotive engineers have their own way of doing things
There should be a vacuum hose diagram on the rad support plate and it would denote a check valve