Jack Bradley

Hi,

I am having trouble diagnosing what is wrong with my Speedometer, at any speeds the needle will bounce. The needle fluctuates with no pattern and is completely random.
I did a test while holding the reset button and turning my truck on. The needle does rotate from one side to the other but it doesn't do it smoothly - it does it with hesitation, almost like its slightly sticking.
I am having trouble getting a clear answer from the internet or anyone local. If you are please able to shed some light on this, and maybe my cheapest way around it.
1996 Ford,
F150 XL
5L Manual

Thank you,
Jack.

Steve83

Click this & read the caption; especially the TSB near the bottom:


(phone app link)

I think you need a replacement PSOM, and they're common & affordable in junkyards (only). If you can't find one locally, e-mail me.

Jack Bradley

Thanks,

It's looking like i'll have to replace the whole cluster rather then just the PSOM module, all local wreckers wont part the two.
The new cluster reads 100,000kms less then my current cluster, is there anything i can do about getting the KM's changed?

Steve83

From that pic that I posted above, click the "PSOM" link at the top of the page to view the whole album; then switch to "Thumbnails with captions" or "Fullsize w/captions", and find the one that describes adding miles. Yes, it takes a while...

Jack Bradley

Hey again @Steve83

So I replaced my Anti locking brake sensor in the top of the rear diff, changed the diff oil in case there was metal flying around messing with the sensor (From my understanding that is where the speedo gets its signal).
I have tried 3 different clusters, all of which worked (Apparently) and are in good condition. Still no success with the bouncing needle, do you have any idea on what my next steps could be?

Thanks,
Jack

Steve83

Stop changing parts, and read so you understand how it works. There are only 2 moving parts in the system: the rear diff, and the needle; and they're directly connected by 2 wires.

Jack Bradley

Hi @Steve83
I'm so sorry to be a nuisance,
I am still having trouble pinning down my issue. I'm looking through all the information you have linked me, I understand there is only 2 moving parts in the system and it is ran through my RABS module which is said it will not interfere with the PSOM - Also having a hard time finding the RABS DLC under my dash, the picture I have found shows it's next to my brake controller, ashtray, and chime plugs. Maybe I need to pull more of my dash apart to get a better view of the wires.
And if its all connected by 2 wires what could be causing me to not get a steady needle? I can see what speed I'm doing because it will sit on the correct speed for almost a second but it drop and freak out every now and then, bumps don't cause the needle to move either.
I just hope I have been navigating the information you have sent me correctly.
Thanks,

Jack Bradley

Could it be as simple as replacing my RABS control module?

Steve83

Not "through" - the RABS simply shares the VSS.It doesn't seem like you understand it, even though you typed it.No, just fold the glove box down & unhook it from the dash. The RABS test connector is behind the glove box hinge. But it's not a likely cause for your symptom. Did you read TSB 96-21-11 in that first caption?