Instrument Cluster

[66Bronco]

Truck in sig. The problem I have is that my speedo stopped working, which means, no cruise control. That said, no blown fuses and I already replaced the VSS with no change. As per the factory service manual, that means I have to now replace the cluster as a whole. Ford no longer makes them new and I don't want to run the risk of putting in junkyard electricals. Has anyone seen/heard/done their own repair to this issue? None of the repair companies I've found have a solution. One has to exist because the speedo signal is what the autos use for shift points.

[351fifty]

Any broken wires from vss back to speedo? And y not just replace speedo alone? Or try changing the wire screen thing on the backside of cluster to keep your mileage correct

[66Bronco]

No broken wires, and if the speedo isn't working, the whole cluster has to be replaced. It's the ONLY part of the modular dash that can't be replaced by itself. Trust me, that was the first thing I thought of.

[JSchuricht]

You don't have to replace the whole cluster. Any cluster from a 92-97 150-350 or bronco should work, you just need to swap the actual speedometer portion. If you want to try to repair it yourself, start simple and relow any broken joints. From there isolate and test all the components till you find the one that is misbehaving. You can rig up a bench test cheeply, just need 12v and a signal generator. You can also use a oscilloscope to test the signal from the VSS.

Here is a video of one I bench tested a few years ago. I used a tone generator software on a computer connected to a larger amplifer for the signal. Video just shows a sweep but you can feed it a steady signal to test a particular speed. Don't remember the signal I fed it but you should be able to dig it up on google.

[66Bronco]

The whole idea is to not replace anything because the odometer i stored on the cluster. At this point I'm getting really tempted to just do a custom dash. I had the assembly out and apart this weekend and there weren't any breaks, so I cleaned the contacts and put it back together; nothing changed. Square one.

[madpogue]

Does the odometer still show the number, or is it blank? If it's showing a number, is it counting up?

[66Bronco]

Odometer still works, as do all other gauges. Speedo is the only thing that doesn't work, and even it tries to read, just bounces and is inaccurate. I'm sure that it's not the ABS tone wheel in the diff because it started going crazy suddenly, not over a period of time. And when the tone wheel is the culprit, the speedo still has intervals where it reads correctly. Worked one day (on a roundtrip to Nashville) and the next day it didn't. Any thoughts?

[madpogue]

If the odometer is counting up the miles correctly, then everything up to the PSOM is good. This must be a physical problem with the speedometer needle. Have you checked to see if it's not just a bent/displaced needle, dragging on the gauge face?

You don't have a "Magnetic Mary, ridin' on the dashboard of yer car", by any chance, do you?

[JSchuricht]

The PSOM could still be bad. If the speedometer is jumping around the odometer will still be counting up, it will just not be as accurate due to intermittent signal loss. You really need to test everything so you can know where the issue is. Jack the truck up and hook a oscilloscope up to the VSS feed. If the signal is smooth while the speedometer is still jumping around than it's not the VSS. Also pull the PSOM and bench test it by feeding it a signal, if it jumps around then it's bad. Another thing to check is the RABS module. The VSS wire splits and goes to the PSOM and RABS, the RABS module can cause weird intermittent issues. I actually have mine disconnected because of it, just pull the glove box out and disconnect the plug in the black box.

[madpogue]

That's why I used the word "correctly". OP has to measure odometer accumulation against a known distance or GPS.

RABS interference is a good call, and an easy thing to rule out (or in).