93lightning2047

My speedometer is bouncing after the 50 mph mark. What do I do to correct this.

mr2medic

I'm having the same problem but mine doesn't start until after 60, I'll let you know if i figure anything out. I'm looking at a couple repair manuals at the moment.

mr2medic

Alright, i'll retype what i managed to find:
Issue: The speedometer needle may waiver and/or a light surge may occur on some vehicles when speed control is used at highway speeds between 50-70 mph. It can be caused by slight dents/chips in either the exciter ring or the Vehicle Speed Sensor (VSS) and air gaps between the VSS and the exciter ring.

Action: Replace the Programmable Speedometer/Odometer Module (PSOM) if required. New PSOM's come with increased immunity to system Variability. Refer to the following Diagnostic Procedure for details.

Diagnostic Procedures:
F-Series: Perform normal PSOM diagnostics per Pinpoint Tests "H" and "J" of the 1996 F-Series/Bronco Body/Chassis Service Manuak, Pages 13-01-30 through 13-01-32 and Pinpoint "B" of the 1996 Powertrain/Drivetrain Service Manual, Page 10-03-11

I think that would give you a good idea of what either you or your mechanic should be looking for, but i haven't figured out where those tests are yet in the manual. This was from a service bulletin dated from 7 OCT 1996.

mr2medic

Ok after reading that bulletin some more here is some more info about the problem:
1. Any slight dents, chips, etc., in either the exciter ring or VSS will create needle waver. Measure the air gap between the VSS and exciter ring, it should be no more than 0.38-0.51mm (0.015-0.020")
2. Check exciter ring runout, should be less then 0.1mm (0.004")
3. If the above items above check out good, then you will have to replace the Instrument Cluster Assembley. Also if they replace the PSOM it is rated at 0.6 hours of labor (36 minutes).

BigRedAlli

The problem with mine turned out to be the new (revised ) sensor. It didn't set deep enough in the housing which caused the gap to be too large.

I never had a problem till one day my speed-o stopped working and the ABS light popped on. Pulled a code for the speed sensor. No big deal, went to the parts counter for a new one and found out it had been changed. Dropped in the new sensor, test drove, and the light was out but the speed-o waved back and fourth so bad I couldn't stand to use the criuse. Constantly surged trying to keep up with the speed-o. Read on here one day about someone grinding on their sensor with good results, so I figrued what the heck! Went back to parts and grabed another sensor and took the die grinder to it. Probaly only took a couple of mm off the base area so it would sit deeper. Swapped it out and went for a drive. Has worked great ever since... Just wonder if it is because of the lighting's thicker rear end housing?

You could have other problems, but this is what worked for me.

Good Luck...

mr2medic

Would anyone happen to know where i can find the diagnostic tests for the PSOM in the Chiltons Repair manual? I would like to know what i need to fix before i start ordering any parts.