Speedometer problem
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Speedometer problem
I have a 1999 Econoline 5.4 (custom day van). Clowns at my last service returned the van with the speedo not working (claiming it wasn't working when I left it with them!).
Trying to figure out what's happened. ABS, Odometer, even cruise all still work. Only the speedo is reading zero (at any speed). Gear change is fine, engine runs fine, only the speedo is non-functional?
From what I can read the VSS (on the diff) must be good or the cruise/gear change would be wrong. Also the odometer is working, so I guess something must be reaching the instrument cluster?
I've checked all the contact and woring in the cluster, but can't see anything (I've re-soldered most joints - I'm an electronics engineer!). However, without any schematics I've no idea what is what, or what to look for.
Any pointers?
Thanks
Allister
Trying to figure out what's happened. ABS, Odometer, even cruise all still work. Only the speedo is reading zero (at any speed). Gear change is fine, engine runs fine, only the speedo is non-functional?
From what I can read the VSS (on the diff) must be good or the cruise/gear change would be wrong. Also the odometer is working, so I guess something must be reaching the instrument cluster?
I've checked all the contact and woring in the cluster, but can't see anything (I've re-soldered most joints - I'm an electronics engineer!). However, without any schematics I've no idea what is what, or what to look for.
Any pointers?
Thanks
Allister
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Joined: Jun 2002
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From: Atlanta GA
It would help to know what service was performed, because that is the area they most likely damaged the wiring. That being said, I would look at the rear VSS in case the harness got jerked from them lifting the vehicle incorrectly.
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120000 mile service
I've looked at all the wiring, including that to the VSS on the rear diff. Looks good, although I'd be more suspicious of that area if the cruise or abs didn't work (but they do).
Does you know how the speedometer/cruise/abs/odometer work? What are the common components (rear diff VSS sensors?) so I can eliminate them from suspicion.
Thinking of disconnecting the rear diff VSS to see if things change (cruise fails. etc.). It's most likely a wire/connection, but without the schematics I don't know how to follow (check) the signal along to the instrument cluster.
Cheers
Allister
Does you know how the speedometer/cruise/abs/odometer work? What are the common components (rear diff VSS sensors?) so I can eliminate them from suspicion.
Thinking of disconnecting the rear diff VSS to see if things change (cruise fails. etc.). It's most likely a wire/connection, but without the schematics I don't know how to follow (check) the signal along to the instrument cluster.
Cheers
Allister
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Joined: Feb 2007
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You claim to have "looked at all the wiring". Can you say Programmable Speedometer Odometer Module (PSOM)? These Black Boxes can be linked to FORD software & many performance chips to monitor what's happening & reprogram the speedometer. Just a guess, but hooking up to the PSOM may diagnose your problem.
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I've nothing but a multi-meter and a knowledge of electronics. If I knew how it's supposed to work I think I could find the problem.
Does anyone know if the VSS is good on account of the cruise, transmission, and odometer working? If so, I can rule that out.
Is there an ECM that takes the VSS signal and then independently drives the said systems, or is the problem more likely in the instrument cluster?
As the problem appeared while being serviced I'm hoping to find a broken connection, but don't know what to look for where.
Does anyone know if the VSS is good on account of the cruise, transmission, and odometer working? If so, I can rule that out.
Is there an ECM that takes the VSS signal and then independently drives the said systems, or is the problem more likely in the instrument cluster?
As the problem appeared while being serviced I'm hoping to find a broken connection, but don't know what to look for where.
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cluster
I've managed to get the workshop manual (although not circuit diagram) and worked through their diagnostic procedures.
All indications are the cluster, so I've ordered a new one. Will let you know if this is the cure when I get it.
All indications are the cluster, so I've ordered a new one. Will let you know if this is the cure when I get it.
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