I'm working my way through this write up: 1989 Ford Truck F 250 4WD Pickup V8-460 7.5L - Diagnosis of the Electric Shift 4 X 4 But struggling. The system is totally dead. Here is what I have:

Check fuses: I read elsewhere the fuses to check were 10, 12, 17, 18 - all have continuity and correct amperage rating
Check grounds: I read elsewhere the three locations: are radiator core support by windshield fluid reserve, next to battery, next to control module behind passenger kickplate. All there ground 0 ohms to battery.
Module passes self test.
Switches have proper continuity and lights work when grounded verified = switches ok
Does have new shift motor

Issues
Check power sources: i have near 12 v to p1 & p2 but p3 I can't find anything. I am probing the light blue/red wire on the switch harness and grounding to ground location by control module and getting no voltage dcv?

Black switch wire 57 to G3 testing wire to ground by control module reading moves around 110 ohms best I can tell

Trans Sensor: testing at module b2 light green 774 wire to b3 light blue 77 wire getting Open line with truck in park (only supposed to be open line in neutral?)
Speed Sensor: testing at module red/white wire 77 how to test? was testing to ground and getting 22.5 ohms
Motor Test: no voltage spike during switch activation testing between A4 and A5 for DCV
Motor Position Sensor: In position edge 2 best I can tell truck is mechanically in 2h Not sure if I can test this way as it doesn't match the chart but get closed readings at B7 B6 B5 open B4 which matches edge 1

I'm sure I'm making errors in where/how I am testing. Be nice if there was someone had made a walk through video to go along with the write up for guys like me. Might be alot to ask for help as this might require alot of homework even if a person knew exactly what they were doing.

 

Does that 4x4 module have self test mode?

 

Yes and it passed.

 

I put it back together after all my testing, cleaning contacts etc. The system is no longer dead my new symptom is the module clicks repeatedly when I push the 4h switch the transfer case motor pulses but doesn't turn (i do have it off of the transfer case to verify it is turning). Any ideas?

 

If the transfer case shift motor isn’t doing anything but you have power there then most likely the motor is bad. Back when I worked at the Ford dealer in the 90’s, they would go bad all the time from not being used. We would let them hang from the harness and have someone push the shift button. You could easily tell if the motor was working since it would flop around when shifting to the next position.

 

I took apart the motor and found nothing remarkable. The brushes suck to put back in fyi. After going through everything in the previously mentioned write up as best I could I put it all back together without finding an issue. Lots of contact cleaning and etc tho. What do you know it works! Hopefully it stays that way.

 

Probably was just stuck from not being used.

 

You really need to activate those little buggers every so often. They are not much bigger than a wiper motor but is required to live in the harsh environment under the truck.

 

It's actually a power window motor but with extra seals to keep out the crud. I used to have to take the motor off of my Bronco every now and again and "reset" it with respect to it's orientation on the transfer case. Then it would start working again.

 

This is the best advise I've read! Since the last post I reassembled the whole system and it suddenly worked after finding no issues. I used it all hunting season this fall without issues until last week it stuck in 4x4 and the whole system was dead. After checking the fuses I pulled the transfer case motor to manually switch it to 2wd and what do you know the transfer case was not fully shifted into 4x4. So to move the transfer case motor back to the 2wd spot I applied 12v to the large yellow wire coming from the motor (I think that is pin 3 circuit 777 or so said another forum) and grounded the large orange wire (pin w circuit 778?). I just used a 12v battery I had laying around theoretically you could use the truck battery in a pinch. If you switch the wires the motor rotates the other direction. The motor has a built in stop at the 2wd position so I powered it up and let it rotate till it stopped, manually switched the transfer case to 2wd bolted it back up and suddenly the system works fine! I'd bet that was my original problem too. To bad I spent hours and hours testing everything in the whole system. Apparently when the system sees the transfer case is not fully shifted it displays as a dead system. I thought I had read somewhere when there is a bad shift it will default back to 2wd. My system just dies. I hope this helps someone out. In the mean time I'll just carry the tools to realign the transfer case and motor in the truck with me.