[cmayer]

So, my ESOF is doing the typical switch to 4x4, hubs do not engage, and AC diverts to safety mode through the defrost system.

Transfer case shifts and all dash lights are functional. Vacuum pump works and appears to operate correctly.

Tested the HVAC vacuum lines and did not find a leak. Also the HVAC system works perfectly up until I switch to 4x4. Check all connections behind the glove box and everything appears correct.

Tested each hub individually and they locked up with 12-14 Hg and held vacuum.

Tested the ESOF vacuum lines from the PVH Solenoid and they held 14 Hg and locked the hubs.

After these steps, the only thing I can think of is the PVH Solenoid. I see there's a way to test the PVH for vacuum leaks by applying 20 Hg to the circuit, but I'm not sure where to apply the vacuum.

Is there anything else it could be at this point other than the PVH Solenoid? :dunno:

Thanks!

 

[NYC F-350]

Check out the pdf file I have attached. It has all the pinpoint tests for the whole system. Everything you ever wanted to know about the ESOF system, and more.

 

[cmayer]

Thanks! Printed it and will diag. this weekend.

 

[robsranger]

Just found. Thanks for the PDF NYC, Helped me!

 

[gbalaz]

Page 308-07A-15...i'm working on diagnosing my PVH solenoid, section I1, it says check if the solenoid clicks when either wire is grounded. On my truck, one pin clicks when grounded but the other one doesn't. Does the PDF mean to indicate that when one outer pin is grounded, it will click then checking the other outer pin when grounded it will click? Or one or the other?

 

[ZMANN]

it means with + to center the grounding of either outside wire should make an audible click

the ground is the signal to engage disengage so either one should make a sound

I prefer to test the actual Vacuum

 

[gbalaz]

I figured grounding the wires, doesn't matter which one should cause the solenoid to click which simulates what the ECM does when signals are sent to those wires. I think i've determined my solenoid is faulty.

My 4x4 system works sometimes but not all the time so I think the vacuum system is working fine. I always get the front diff to engage but the hubs are not always locking.

 

[06kingf350]

Not to hijack the original post, but i have a similar / related question and thought better of starting a new thread.

My ESOF stopped working a few days ago and defrosters came on full time (whether switched to 4WD or not). After some troubleshooting with a vacuum gauge and fixing a few questionable hoses, I found that the PVH solenoid inlet (the lower vacuum hose connection connected to the vacuum reservoir through a red hose) simply vents to atmosphere all the time. Attaching a MityVac or even sucking on it the old fashioned way, and I can draw air right through the PVH solenoid.

As a result, the vacuum pump can't build vacuum, and ESOF and HVAC doesn't work.

Fine, I think, and pick up a new PVH solenoid at the Ford dealer. Back at my shop, it holds vacuum at the inlet, like I imagine it's supposed to. Pop it on and voila, everything works... For about 30 minutes. I stopped for fuel and when I restarted, same old symptoms returned. Checked the PVH solenoid and once again, I can draw air unrestricted through the inlet port.

I worked around it by disconnecting and plugging the hose that normally connects to the PVH solenoid inlet and just manually locking my hubs. HVAC now works fine and the vacuum pump goes off a minute or so after startup, both of which mean that the rest of the vacuum system is sealed and working properly.

Here's the question: Could I possible have a brand new PVH solenoid that failed just like the old one? Could the very cold weather here lately (-9F or so in the mornings) be causing even a new PVH solenoid to misbehave? Has my wiring harness gone funky and started nuking the PVH solenoid somehow (it passes the normal 'check for clicks by grounding the outside terminals' test). My spidey sense is tingling. It doesn't seem likely. What am I missing?

2006 F350 King Ranch 6.0L CCSB