Western Star Gauge Problem-This is Bizarre!

we have tried a new ecc and still nothing

 

The ECC doesn't have anything to do with the gauges directly. From what you describe it sounds like their not getting their signal which comes from the RX module. The RX gets all the relevant information and sends that up using a dedicated databus to the speedometer, where it's daisychained out to each gauge. It's possible your speedometer can be causing it, no real way to test it unless you have another to test. I'd check your rx module, it sits on the engine side of the firewall below that clutch peddle. maybe they unplugged it.

 

We had one of thos rx modules sent to us by mistake when we ordered the ecc that the freightliner dealer said controlled the gauges, but they're not much help around here, we replaced the old rx module with our new one and still no gauges, ill try and see if we can get our hands on a speedo

 

I don't have any technical info on the Stars but most data bus setups have a terminating resistor on each end. When the resistors go bad it can cause some real screwy stuff to happen.

 

I looked up your age of truck and made one mistake, your rx and speedo connect to the 1587 data bus separately, the speedo picks up what the rx sends out on the main bus, and gets the rest of it's info from the main bus. I'm use to newer trucks where the rx is connected to the 1939 data bus and then the speedo is connected to the rx module directly using their own special 1587 bus and the speedo, and thus the gauges get all their data from the rx.

The difference now is that everything the speedo displays is picked up from the 1587 bus and not all of that gets transmitted by the rx (rpm, oil pressure, etc). You've already replaced the rx since you were sent one so we know that's not the problem.

Do you have a datastar in the dash? If so and its working fine then I'd point the finger at the speedometer.

I think it unlikely the issue is with a terminating resistor simply because if the main buss was missing one, or had some other issue, you should notice other issues, and I'd think the gauges would act weird instead of doing nothing at all.

One other thing to check I just remembered is the daisy chain wiring between all the gauges themselves. they all have the same connector on the back, and the speedo has one too. If the one connected at the speedo has a bad wire in it then none of the others will get a signal, you can move the connectors to different gauges so I'd try changing which one is connected to the speedo. I've seen that before.

I also don't think its a ground issue because there is a common ground in the speedo that everything uses and the gauges illuminate.

If your still having an issue with this I can get you wiring schematics if you give me the last 6 of your vin.

 

Thank you for the info Mythandar, i did not have a chance to work on the truck today but i can answer a few of the things you pointed out. It does have a datastar in the dash and it was not working at first, it kept saying no data available, now it started showing temps only(coolant, diffs, and battery voltage) we did not do anything it just randomly showed up one time we turned the key on and it is showing every time now. The truck also runs perfect with none of the gauges working. A wiring schematic would help a great deal, we can only seem to find ones for newer trucks. The last 6 of the vin is W75554. I will try switching the connectors on the daisy chain tomorrow and see what happens there.

 

Here you go. Cab-page 4 shows the speedo and datastar, you can see how they are connected to the same wires and that goes through J15ENG connector to engine-page 1's J15ENG where it connect to the engine ECU's 1587 spliced with the RX modules 1587 wires. They show power and grounds on page 4 for the speedo. For fun I'd check fuses f20(ecc-lightbar), and f140(drl power) as they supply the ignition and battery power to the datastar and speedo, unlikely but worth checking. Let me know if you need anything else.

 

Just a quick update we found the issue. The people that painted the truck took the plug to the data link on the firewall and plugged it into the marker lights on the side mounted air box. I appreciate the help Mythandar

 

I have 2006 star my speedometer is working my data star works but none of the rest of my guages dont work. Anny suggestion