Western Star Gauge Problem-This is Bizarre!

I am not positive on your Western Star as I have little experience repairing Western Star (plenty of experience on their sister brand Freightliner as well as International) but it sounds like a multiplexing system which has become common in most vehicles over the last decade, each gauge has a unique address, you do not actually get the signal from the sending unit directly to the dash it goes thru the VPM or ECM first then the data is sent over a common information bus to several different systems and points in the truck at the same time. Gone are the good old days where you can easily trace a problem, for this system you need a logic probe, computer that can read the data bus, and the factory programming for the signal so you know what you are looking for.

 

look underneath the floor on your driver side from the firewall. You will see a box that the pyrometer probe wiring runs to. I've seen this being an issue on a couple trucks.

 

I doubt it. I think the gauges are specific to the multiplex system and the only way you could do that is if you used the gauge from the prior trucks like in my 2000. The gauges still look the same

 

This sounds like the beginning to a ground problem. If you start experiencing problems with all your gauges, the likely culprit is corrosion to the ground wires from the cab to the starter or frame. Check the resistance diffference at the the firewall cluster in the engine compartment compred to the large wire at the starter or frame ground.

 

YUP. what he said. go over ALL connections between batteries, frame, starter, everything. also, those data boxes DO go bad. dealer can check it for you. the solution you found by using a mechanical gauge is certainly the easiest.

 

I have a 2006 western star 4900sa, i am having issues with all the gauges not working, all of the grounds appear good and the gauges will light up and make the sound like they are cycling but none move except for air gauges because of air line pressure to the gauge. i am getting 4.7v on the signal wire to the gauges, im wondering if there is a ground somewhere that i am over looking does anyone happen to know were the gound for the gauges is located. We have spent a week banging our heads against a wall trying to figure this out. (Gauges worked fine untill we sent the truck to get painted, only thing we know is they unhooked the batteries, pulled the doors off and pulled off the hood. they climbed around the engine bay to paint the top of the cab but all connections look to be good. Gauges haven't worked since truck left the paint shop)