Alright, been chasing my tail for a while, replaced about everything I know how to, now back to the drawing board! this is not a vaccum problem, please do not ask if my heat is only defrost, etc, were way beyond that.

truck is a 2000 f250 7.3 6spd. 206k on the clock these days.

so about 3 months ago i ran into my esof switch no longer doing anything, so i ran through the basics of checking fuses, relays, etc, everything was all smiles. I did find I could randomly by pulling the GEM fuse get it to cycle into 4wd. but this was not very common. after a week of driving around in 2 wheel ,i pulled the tcase motor off, manually engaged 4x4 and locked the hubs in. bam, obviously it works, everything is mechanically locked. For ****s and giggles, I threw a new shift motor assembly on, still nothing. A week or so later, got a new switch, nothing.

after all that I was still not getting anything from the relays under the hood, no vaccum pump turning on trying to do the hubs, absolutely nothing was trying to do anything. a few more weeks of being pissed and leaving it in 2wd in MT winter, I finally broke down and bought a brand new Gem unit thinking it was the last straw.

Just got it put in tonight, and again, NOT A DAMN thing. when i first hoooked my t-case motor back up ( i had to manually do 4x4 again as we had some serious snow recently) I could here the motor zero out really quick and make a quick back and forth cycle. so something did try and happen, or who knows.

Flipping the switch i still get 0 reaction from the relays under the hood, vaccum pump, etc.

if anyone has any ideas of where to go from here, by all means, I have a nice multimeter and understand how to test circuits, components, etc.I just need some damn direction right now!!

so yeah,

new shift motor
switch
gem
no results.

 

Can you be more specific on your symptoms?

This doesn't tell me anything except your opinion. How do you know this isn't a vacuum problem?

Again, this tells me nothing. When you switch to 4H, what happens?

What does happen? Does the motor shift the transfer case? Do you have a 4x4 indicator light in the dash?

 

I had to laugh at that

Do you have access to the wiring diagrams ? Or the Ford diagnostic tree for the electric shift transfer case ?

If not PM me an email address and I will see what I can get for ya ..... sounds like your just haveing a control issue. Its a pretty simple system except the part about it being controlled by the created by satan GEM

 

also do you have a scanner that can pull codes ?

 

thanks kaz, shooting over an email adress to get the wiring diagrams.

redford,

it not being a vaccum problem is not an opinion, i have been through every part of the system up and down to everything besides checking out wiring harness issues is all i have left that i cannot confirm, the switch is not doing anything, the relays under the hood are not reacting, the vaccum pump is not being commanded to come on, no power is being sent to the t-case shift motor (obviously due to relays not seeing power) this system is not insanely complex.

im not trying to be rude, but its far from my first time diagnosing electrical problems, I build full custom turbo snowmobiles and have done electronics development work for a few years on them as well, so I more or less need some direction for my truck as I dont have all the wiring diagrams available right now and there are just 10x more piles of wires to wade throught then I am used to.

 

Google 2001 F-Super Duty 250-550/Excursion/F-53 Motorhome Chassis Workshop Manual You might find a link... (section 308-07A and don't ask how I know...)

I doubt if there is much difference between it an the '00.

Good luck

 

haha, i cant imagine how a guy would have such info logged in his head, maybe some troubles yourself eh?

that was easy once i had the name of what i needed to search for, favorited and reading up, hopefully this sends me in the right direction.

anyone know what kind of reader I would need to get codes out of the gem? i want to say i need like AE or something of that nature?

 

If that response was to me, let me assure you I have tons of "info logged in my head", much of totally useless! I admit I did a copy and paste on the title. It is bookmarked on my computer. That way it cannot be displaced by other useless information in my head!

I am going to see if I can pull codes this weekend, but don't have a reader, so will have to try to find someone with the right one. I do not know what to recommend for that, but others here can help.

Yes I too am having a problem with my ESOF. I installed a new Pulse Vacuum Hublock Solenoid (PVHS) last fall. it worked fine for a while but it failed sometime in November. The "engage" solenoid is shorted and stuck in the open position, putting full manifold vacuum to the hubs. They would not disengage. I've pulled the vacuum lines at the PVHS, reset the hubs and am engaging them manually when I need 4X4. Everything else works fine, and the hubs hold vacuum when tested with a vacuum pump.

I'm at step G5 now and will ohm out circuits #145 and #605 from the PVHS to the GEM this weekend, and check the GEM connector too. What I cannot find is any value for the ground resistance check through the GEM, other than "greater than 10,000 ohms." Mine showed 6.47 and 6.57 K-ohms, using a Fluke 87 autoranging multi-meter.

I'm hoping someone can let me know what a working system measures to ground through the GEM.

I don't want to sacrifice another PVHS if something else in the system is causing them to fail, so I'm still digging around.

Anyway, hope the link helps, and I am interested to know what you find. Good Luck!

BTW, where in MT?

 

ill be honest, looking forwards at this project, im not sure how much time and effort im ready to continue to dump into it. ive never been one to give up and drop it at the shop, but im not sure my mental stability is up to diagnosing this madness. we shall see.

and im right outside of bozeman montana.

althought no 4wd has been sort of a blessing, havent pulled the enclosed sled trailer all winter, been having others haul it for the first season now!

 

I know the feeling, but am also pretty stubborn about this kind of thing. I'm not ready to let it go, myself.

 

Last year when mine quit working, I had nothing happening with the switch. It turned out to be 2 problems. One of the relays was bad and the shift motor had a striped gear. I started having problems again Friday night. Post entitled "DTC P0603 & P1729." I'll be pulling the shift motor off again tomorrow. I think I may have gotten water, mud, etc. in it.