So I was driving today and my ac decided it didn't want to go through any vents other than defrost, looked it up and everybody said check the vacuum reservoir, did this and chased the vacuum all the way to the hvac controller, the black vacuum hose has vacuum all the way there, is there anything else I can do or is it time for a new hvac controll unit?
edit: forgot to mention the white vacuum line that runs with the black line has no vacuum in any position

 

The black line that runs from the reservoir thru the firewall to the Controller is the Vacuum Source for the controller
The white line in the cab, turns to grey in engine bay is a controlled vacuum, so if there is no vacuum on the black line then there could be no vacuum in the white line, just FYI

So you found the Vacuum reservoir
It will have 2 lines, one runs to the firewall the other to the engines upper intake, this other line is how the vacuum reservoir gets its Vacuum, trace this line, or unplug it from vacuum reservoir and start the engine
See if this line has vacuum, put your finger on it should hold tight to your finger, if not then this line is disconnected or broken


The Climate controller for vacuum distribution rarely breaks in Rangers, and if it did you would notice a HISSING sound of vacuum sucking in air, so in the absence of that its more likely vacuum is not reaching the controller, so problem is in the engine bay

 

The line has vacuum at the reservoir, and then tracing it further up there's 2 places it has connectors, both of these have vacuum as well, where does the grey/white vacuum hose get its vacuum from? I notices it goes to a little controller type thing on the heater core hoses

 

Grey/white line gets vacuum from controller in the cab
The white line in the cab from the controller has a splitter(T) under/behind glove box where its connected to the Fresh Air vent valve in the cab, then goes out to the grey line and the Heater By-pass valve in the engine bay

When you select MAX AC on the controller the vacuum is applied to the Fresh Air vent valve, closing it, so the fan/blower then pulls in "already cooled" Cab air for re-circulation, and vacuum also closes the heater by-pass valve, in engine bay, so no hot coolant is circulating thru the heater core inside the cab, so less radiated heat in the cab

This vacuum can also be applied to the white line when selector is in the OFF position in some years

Diagram of the Cab control Vacuum system: https://www.ford-trucks.com/forums/a...ntid=517&stc=1

A bit hard to follow
When you turn the **** you are turning all 4 selectors at the same time, which connects and disconnects the red, yellow, blue and white vacuum lines to the Black line(vacuum) from reservoir

If you fold down glove box all the way you will see the Vacuum manifold on the left, the black, red, yellow, blue and white vacuum lines, this is another good test point

The Blend Door is electric, not vacuum controlled, it is operated by the separate Temp ****

 

Are the red yellow and blue vacuum lines in any way tied to the ones in engine bay? Other than through the blacks source vacuum? The reason I didn't have vacuum at the white is because I thought it would have vacuum in ac, at max ac it does have vacuum. Is there a fuse for the selector that controls where the air goes?

 

No, only the black line from reservoir connects engine bay to cab vacuum lines, with the exception of the grey line all the other engine bay vacuum lines are for engine controls, i.e. EGR and EVAP systems

No, there is no electrical component to the air direction vents in the cab, its all vacuum controlled

Just the Temp control is electric

 

What do you recommend I try to do? I have vacuum hose that's the right size so I think im gonna replace all of the black lines as preventative maintenance cause they're preeetty brittle

 

Is the air direction control working again?

The hard plastic vacuum lines do get brittle from the heat in the engine bay, especially near the exhaust system, they are usually OK in the cab
So sure, replacing this line and the line to the engine is OK as preventative maintenance

There is a Check Valve on the line from reservoir to engine, usually looks like this: https://i.ebayimg.com/images/g/66UAA...q/s-l1200.webp

 

Still not working, they were very brittle though, definately would've cause a problem some time soon. I am missing that check valve, what is it's purpose? Could that be my problem?

 

This is the closest i got, would the 4x4 model use this as a check valve?

 

No, that's the PVH(pulse vacuum hub) switch but can cause vacuum leak for the reservoir
There should be a "T" on the line from reservoir to cab that connected the PVH switch to reservoir vacuum

Reservoir-----------------(T)---------------------------------------cab
PVH switch----------------/

PVH switch sends pulsed vacuum to the front hubs to engage 4WD, so needs a steady vacuum source when in use
This setup was only used from 1998-2000 Rangers/B-series 4x4s
Many removed the PVH system/hubs in favour of Manual Hubs which were way more reliable


Engine vacuum is 18-21" of negative pressure at idle and when cruising, but when accelerating it drops close to 2"
Vacuum reservoir is used to maintain a steady 16"(or so) of vacuum regardless of engine vacuum at any given moment

The Check valve is there for that purpose, its on the line that runs from the reservoir to the engine's upper intake, where vacuum "lives", lol
It allows air from the reservoir to be sucked into the intake, which creates that 16" of negative pressure, but doesn't allow air to flow in the opposite direction when intake vacuum drops during acceleration
So basically a "flap" that limits air flow in one direction only
Without it your air direction vents should work at idle, but as soon as you were accelerating(vacuum dropped) the vent would change to Defrost until you got up to speed and were cruising, steady engine RPM
No vent control means no vacuum at all at the cab control, or very weak vacuum so a leak

Your Power Brake Booster has a Check Valve for the same reason, the Booster part is large because it is also a Vacuum reservoir, so even if engine should stall while driving you would still have 3 or 4 power assisted brake pedal pushes before assist was lost

 

I'll have to see if napa has that check valve tomorrow, til then I'll have to find my vacuum gauge and see how much vacuum the cab is getting. If I were to bypass the vacuum ball and connect cab straight to engine for testing purposes nothing bad would happen right?

 

No, nothing bad would happen

You can test vacuum at the grey hose in the engine bay, just put the selector in the cab on MAX AC or OFF, and it will show you vacuum AT the selector since it is passing thru the selector

 

Alright so I think I've narrowed it down to the vac ball, I have 20 inhg of vacuum at the red off the engine, 20 inhg at black at vph thing, then 2 hg at the black hose going into cab as well as at the grey in the engine bay

 

Ball must be cracked
Used are a safe bet since you can test them before buying, see if they hold pressure, new from Ford they are $25us so not too expensive

 

Thank you for all the help! You're great man, I didn't think it was the vac ball cause spraying it with carb cleaner the engine didn't rev at all, but thank you again!

 

Once you have it out put a hose on it and put finger over the other port and blow, should hold pressure of course, might be able to fix it with JB weld or similar hardening mixture, its a "vacuum" ball so sucks IN, if doesn't try to blow OUT patches, it tries to hold them in place
Its why the smaller vacuum lines don't use clamps, no reason to

 

The vac ball only hold vacuum going one way, the larger Id hose holds vacuum no matter how hard I suck, if I go to the smaller id hose it sucks air from the other one. If I plug it when I stop sucking the small id hose nothing happens, then release large id and all pressure releases. This has me confused now

 

It has a built in Check valve, some did, wasn't common on Rangers, so your ball is OK if it holds pressure

 

Interesting, so then maybe the 4x4 **** is leaking, I'll have to search through that

 

PVH switch has 2 vacuum lines, one goes to the hubs, other goes to vacuum line from reservoir, unplug that line and put a screw/bolt in the line or tape over it to take it out as a possible leak

 

Putting o2 sensors in after work then I'll do this. Shouldn't it only let vacuum through with 4x4 on though?

 

Yes, but valves leak

 

Sorry for the late update, some **** came up, but it is the 4x4 actuator thing leaking, so I routed the vacuum excluding the 4x4 and will just get manual locks, is it able to go into 4x4 with no vacuum? Just unlocked front axle right?

 

Yes, you can shift in to 4high or 4low but won't actually have 4 wheel drive until you can lock the front hubs