Howdy all,

my 2000 7.3 F350 just got out of the shop.

replaced both vacuum pumps. 4x4 pump had no vacuum and heat pump was ticking.

problem is, my ESOF still doesnt work. So the problem IS NOT vacuum. I can still manually lock my hubs and get into 4x4, but I was wondering what the next thing to look at would be.

And will it be expensive?

thanks

 

Have you checked the hoses to the hubs and the hub seals??

 

Does your ESOF switch have any lites as you switch it?
on my 03 F350 7.3 no lites, but with engine off, key out, put ESOF switch INTO 4 H, then start engine and it will go into 4 H, but to get it back out, I have GROUND momentarily the relay in relay box, inside engine compartment, drivers side corner, mounted on inner fender, next to firewall.

I know that sounds crazy, but it works on mine. On mine, the ford shop manual/ and my trying to decifer it, lead me to believe it’s the vacuum pump system- nope, further tracing schematic led me to believe it’s the ESOF switch- nope, more tracing and reading led me to pull my hair out( the little that’s left) because the schematic is wrong, it’s for an 04, note an 03, then I narrowed it down to the 4x4 “brain”, passengers side dash, take glove compartment out, swear lots, and remove little black box, it only has about 23 wires going to it(LOL) it’s expensive, ford was $400, auto wreckers was $100, nope, same thing. After that, seriously thinking about giving- selling- ( to someone I wasn’t happy with-LOL) but after settling down, next test- according to ford schematic, was test electric motor (4x4) on side of trans, could not find good used , so another $300 and put in new, and holla- nope- so after much talking to the big guy upstairs,
taking stock of what I had done- relays, making sure I had 12v to ea relays ,1 for in, 1 for out of 4x4, vacuum pump relay, ESOF switch, 4x4 brain box under dash, ign switch, 4x4 switch motor on trans, finally found GROUND wire for ea relay in engine compartment, I could momentarily ( no more than 3 secs) I could put it into , or out of 4x4 , yup, pain in ***, but can be done, if needed.

After many hours soul searching and studying, the not very good schematics in ford manual, figured there has to be a broken wire somewhere, probably between ESOF brain box under dash and relays in engine compartment. It was after all this, that I lucked out and found that if I put ESOF switch into 4x4 H, before I turned key on, that it would go into 4x4 when I started engine. So when I followed elec path on start, on schematic, there is a different path on start up, but not for shut off by ESOF switch, or ignition switch off.
I know this is “heavy”, but consider my “brain” finding all this out( LOL )

So if anyone knows which wire is the culprit , pls let me (us ) know. I am sure there is other owners out there with same problem.
Good Luck!!

 

OK. ESOF= Electronic shift on the fly. In order for anything electronic to work properly, it needs a COMPLETE circuit. Make sure everything is properly grounded. Many times in my 74 few years chasing electrical issues it has turned out something was not grounding right.

 

For sure, thank you . I plan on finding all grounds points from that circuit, starting under dash. It’s hard on my head fumbling thru those schematics when I have to keep in mind they might not be right (as I have already found out- and in this circuit)