1994 f350 od light flashing, #8 fuse popping. need help please

[icemannocal]

Hello,
First time diesel owner and first post.
6 months ago I bought a 1994 f350 idi turbo with 100,000 miles. Nice truck, perfect condition looks new and all stock with the exception of 4 inch lift and banks turbo upgrade.
For 6 months it drove like a dream. Now I am waiting to have new injection pump Installed due to heat soak. I guess this is normal with these miles.

2 days ago my #8 fuse popped, od light came on, speedometer and odometer went out, and transmission went crazy on me. I think it's all the same problem (the fuse) but there must be a direct short somewhere because it pops instantly when I replace, and the truck is not turned on when I change fuse.
I hooked up diagnostic tool that I just bought and got fault code 29 (vss). When I unplug vss all power is restored to speedometer ( after New fuse is installed) and fuse does not blow. I replaced vss and it did nothing, I have same problem blowing fuse instantly when harness plugged into vss.
I need help on what to try next, where does the vss wire go to after it leaves the differential cover? I am thinking the wire is shorting somewhere? Or????
Thank you in advance for any help.

 

[crash-harris]

Welcome! Start pulling those 2 wires out of the loom and track them down. I bet either aomething has melted or just one is sticking out somewhere and rubbed through the insulation.

 

[FORDF250HDXLT]

PSOM & Odometer Not Working & E4OD Harsh Shift TSB 94-09-12; "...PSOM (Programmable Speedometer/Odometer Module) may be inoperative or not function properly and the #8 fuse may be blown. In addition, if the vehicle is equipped with an E4OD transmission, it may exhibit a harsh shift. These conditions may be caused by trim screws installed through the 17K745 visor wire between the left hand "A" pillar and the left hand visor bullet connector..."

Tape the damaged or exposed wire conductor and add scrolling to protect the wiring from trim screw shorts. Refer to the following service procedures for service details.
Remove the garnish moulding.
Inspect the wiring condition against the trim screws.
Check screws for burn marks.
If burn mark is found, use electrical tape to protect exposed/damaged wire. Add 1/4" (6.35 mm) scrolling to maximize protection.
Replace # 8 fuse.
Reset the PSOM to see if it is functioning properly.
Reinstall trim.
Recheck fuse #8 and PSOM final verification.
=========

and/or
ISSUE: Some customers may have concerns that the following features are inoperative:
All courtesy lamps
Map lamps
Engine compartment lamp
Glove compartment lamp
Odometer in the instrument cluster
Dome lamp
Power mirrors
Lighted vanity
Cargo lamp
Remote keyless entry

This is due to insufficient clearance between the outer roof panel of the cab and a map/dome lamp mounting screw, causing a short in Circuit 54, which causes Fuse 8 (15 amp) to become inoperative. This fuse protects the wiring for the above vehicle features.

Replace existing dome mounting screws with new, shorter screws. Refer to the following procedure for service details.

Three (3) screws (52814-S36) are required to mount the map/dome lamp to the inner roof panel of the cab. Two (2) of the three (3) screws are used to complete two (2) electrical circuits, 53 and 54. Circuit 53 is after the lamp switches and is "cold" ("cold" means that 12 volts are not present) and Circuit 54 is before the lamp switches and is "hot" at all times ("hot" means that there are always 12 volts present).

The 52814-S36 screw is approximately 25.4mm (1") long. When there is a sufficient amount of downward force applied to the outer roof panel of the cab, the panel will make contact with the screw that has Circuit 54 (12 volts) on it. For example: When the brushes and dryer pass over the roof of the truck in a car wash or when traveling at highway speeds. As the roof panel contacts the screw, it causes a direct short-to-ground. When this occurs, Fuse 8 will be overloaded (15 amp), open and disable the listed features.

Carefully pry pillar/dome lamp lens from interior lamp body.
Remove screws retaining interior lamp (map/dome) to roof trim panel.
Install new screws (52802-S36, 19mm).
NOTE: ANOTHER OPTION WOULD BE TO REMOVE OLD SCREWS AND CUT/GRIND APPROXIMATELY 6.35mm (1/4") OFF THE END AND REINSTALL.
Reinstall pillar/dome lamp lens.

PART NUMBER PART NAME
52802-S36B Screw (19mm)


upgrade the whole works;
http://www.oilburners.net/forums/sh...uck-pic-heavy)&p=775477&viewfull=1#post775477

 

[OLDBULL8]

My grandson had the same problem, blowing #8 fuse drove us nuts to find the problem. It was the damn dome light.

 

[icemannocal]

Great information, thanks, I am going to work on it now, I will post up what I find.

 

[icemannocal]

Well unplugging the vss plug at the differential did not have the same results as yesterday, fuse still blew with it unplugged so
That is odd. I checked wires in the loom running from pumpkin to where I think it goes to and that's the firewall. I found no problems that I can see, it's tight inside the loom.

I removed driver side viser and did not notice any of the 3 screws with burn marks, stuck my finger up in the hole and did not feel any wires where the screws were.
I removed the dome lamp and everything looked good, just incase I grinded the screws down about 1/4 inch. I pulled cargo lamp off and all wires looked good.

Anyone know how I can get a wiring schematic, I am curious where other end of vss wire goes, I believe it went up to firewall but it's tight in there. Wire color was green with a black stripe and other was red. I Had to call it quits due to I popped my 10th fuse and am stranded till tomorrow to get more. I don't want to take any chances and drive it.

 

[FORDF250HDXLT]

check your door jam switch too?

 

[icemannocal]

check your door jam switch too?

I will check everything you tell me to. It's going in on the 29th for an injection pump, just trying to save myself some shop labor for this added problem. Thanks for your time and help.

 

[FORDF250HDXLT]

if you can think back at the time you unplugged the vss........did you happen to leave the door closed? perhaps the fuse wont blow until you open one of the doors? if so then you'll know the issue is in the wiring at one of the door jam switches.all you need is a screwdriver.1 screw and comes right out.you might find a bad switch or chafed wires right there.
it's gunna be something kinda simple like this,most likely.
do you have the power mirrors? see the whole list there on the fuse and peak around at the wiring going to each thing.you'll find it.
most often it's in the dome light screws.you got unlucky lol.

All courtesy lamps
Map lamps
Engine compartment lamp
Glove compartment lamp
Odometer in the instrument cluster
Dome lamp
Power mirrors
Lighted vanity
Cargo lamp
Remote keyless entry

 

[riotwarrior]

I will check everything you tell me to. It's going in on the 29th for an injection pump, just trying to save myself some shop labor for this added problem. Thanks for your time and help.

Where is this truck going...check hall of shame.

Where is injection pump from...check hall of shame