98 4x4 xlt no spedo

[Bigstick1973]

Hi i have a 98 ext cab 4x4 auto tras. the spedo will work for about 12 miles before going dead. i changed the vss in the rear end and still the same. i have no check engine lite or abs light on. when i got home today i pluged my scanner in and drove it around the block. the scanner showed mo codes but did show my speed as i was drivig even tho mt spedo was reading 0. any ideas?
Thanks

 

[RonD]

Problem will be the speedometer itself or it's wire on the back of the instrument cluster

Does odometer work when speedo is off, or do they both stop at the same time?
Odometer uses the same signal wire but different "motor"

VSS wire goes to ABS directly, but is spliced off to GEM(generic electronic module), the GEM is programmed with stock tire size, and corrects "speed signal" for tire size then sends out that VSS signal to computer, cruise and speedometer.

So computer, cruise and speedometer share the same signal from GEM
Computer is getting the signal, so VSS and GEM are working
Try cruise if you have it
But speedo is either not getting the signal or is broken
Speedometer is run by an electric motor, driven by the speed signal

Thread here on calibrating electric speedometers: http://www.ranger-forums.com/general-technical-electrical-18/calibrating-speedometer-needles-134925/

The speed signal wire will be a Grey/Black stripe wire in #1 pin on center connector on the back of the dash.
If odometer is working then this wire is OK, if both quit working then you will need to test wire and connection

Other pictures here: http://www.explorerforum.com/forums...orks-but-odometer-doesnt-i-fixed-mine.247368/

Check the worm gear it was a common failure for odo

 

[Bigstick1973]

YES Cruise works even with no speedo. and yes the spedo and the odometer stop working at the same time.. also it seems like it only happens afer i drive it for about 20 min. from a cold start. if i shut the truck off and let it sit for awile maybe a hour and get back in it it will work again for about another 20 mins.
Thanks for the reply. truck does have 268k on it.

 

[RonD]

Could just be corroded connector on the back of instrument cluster, as it heats up resistance goes up and it loses signal.

There are 3 connectors on the back
C214, C215, C216

Pin 1 on C215 is the speed signal, grey/black stripe wire

But could be other things as well, like the speedo/odo cluster itself, I would check around to see if you can find a replacement, don't get it yet but just find it in case you need it.

Speed signal is an AC voltage signal, only way to test wiring is with signal from VSS, and it generates it own AC voltage........
So only way to test it is to get rear wheels turning so VSS generates some voltage, i.e. jack up the back end and put it in gear.
And since it takes 15-20min for problem to show up.........that would make testing tougher.

The 1990-1997 Rangers used a gear driven VSS, like this: http://www.therangerstation.com/tech_library/images/speedsensor.gif
These were used with speedometer cables, AND had VSS for cruise and computer, 2 wire plug in
If you could pick one of these up at a wrecking yard, pretty much any Ford from early '90s would use this, then you could use a variable speed drill to generate VSS AC voltage to test speedo/odo

 

[Bigstick1973]

well if im going to take the one i have out to check the wires may as well replace the whole thing so i have one coming off of ebay. will update when i get it installed. thanks!

 

[Bigstick1973]

Ok replaced Gauge cluster and as of now it seems to be working fine. i got a used cluster off of ebay i guess i should have checked the bulbs looks like ill have to pull it back out and replace 3 or 4. i guess if the bulb is black it is bad? but my spedo seems to be working with the new used cluster.
Thanks!