94 f350 speedometer failure.

[kendawg69a]

Speedometer failed due to rabs wires deteriorating. Started fluttering at certain speeds then stopped working at all causing limp mode every time I pressed the brakes. Disconnected abs and now runs. Wondering which of the 2 wires is causing this. there's red and then green with black stripe. Guessing red is power which it seems to have because odometer shows up but has stopped counting. would anyone know which wire is the problem and or will my speedo need replacing? Thank you

 

[madpogue]

Power to the cluster is completely separate from the sensor circuit. Is it the wires to the VSS that are failing?

 

[kendawg69a]

Yes and it's hard to trace I can only see about 4 ft of wire and I can't find anything similar besides old home security wire. Where does the vss connect to from the rear?

 

[madpogue]

There's one main harness running the length of the frame, and it includes the VSS wires. You're going to have to continuity test each of the two conductors, at each connection between the VSS and the PSOM. Typically, if there's physical damage, it's someplace visually evident; the hard-to-reach parts of the harness that run inside the frame c-channel alongside the front fuel tank, etc. are pretty well protected.

 

[kendawg69a]

Continuity tested good. Connector is good what else could be the issue?
Fuses are good

 

[kendawg69a]

Fuse is fine

 

[BDCarrillo]

Gauge itself?

 

[madpogue]

^^^^^ Or the VSS.

 

[cpdenton]

On this year model, here is how it works.

Vs in the rear end sends a signal to the Programmable speedometer odometer module, or PSOM, on the back of the speedo. This sends a speed signal out to the speedometer and also to the transmission control module. Also, to the cruise computer...

Sounds like a bad connection somewhere along the way, perhaps at the rear of the PSOM.

 

[BDCarrillo]

Where's the ABS module in that sequence?

 

[cpdenton]

Piggybacked in the rear end vss. Not really tied in with the speedometer working, but, if it is getting bad signals, and was activating the abs, it could be throwing off the shifting.

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[kendawg69a]

Vss is fine. First thing replaced even though I knew it wasn't the problem lol. Thanks for the diagram

 

[kendawg69a]

Cruise no longer works and also side mirrors aren't powered any more doubt both would go bad at same time. Don't think cruise control worked since ford put there abs attachment on there for recall. Mirrors are same fuse as speedo