I have a cat 938F that we have been having issues with the quad gauge monitor that shows , fuel , engine temp, trans temp and hydro temp . When you cycle the key the gauges will sweep as like they are supposed to however 80-90% of the time none of the gauges will read . Every once in a while running the machine the gauges will come alive , read correctly then go out. Recently the gauges began working ( they worked for 3 or 4 days which is the most we’ve ever had them work. Got in machine today and once again they are not working . We did order the quad gauge monitor and that did not change the issue . Any help is appreciated
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CAT 938f quad gauge issues
- Thread starter Caincon
- Start date
Nige
Senior Member
An expensive Parts Cannon for no result.........
You need the electrical schematic for a start. Post a Serial Number please.
Nige
Senior Member
I'll send you an electrical schematic. Keep an eye on your message inbox.
A couple of questions for a start: -
1. Do all the gauges in the quad gauge assembly sweep full scale every time when you turn the key to ON.? The "every time" part is important.
2. Does the tachometer/speedometer display behave the same as the quad gauge assembly when you tuen the key ON.?
3. Does the speedo/tach module display correctly when the machine is operating.? In other words does it show ground speed, engine RPM, and the selected transmission gear.?
A couple of questions for a start: -
1. Do all the gauges in the quad gauge assembly sweep full scale every time when you turn the key to ON.? The "every time" part is important.
2. Does the tachometer/speedometer display behave the same as the quad gauge assembly when you tuen the key ON.?
3. Does the speedo/tach module display correctly when the machine is operating.? In other words does it show ground speed, engine RPM, and the selected transmission gear.?
Nige
Senior Member
Here's another question. On the display window of the Monitor System Panel (RH dise of dash) an icon SERV CODE should appear when you first turn the key ON. At the end of the panel self-test does that icon disappear or stay on.?
Sorry for delayed response . Gauges only do 1/2 sweep. To my knowledge they used to full sweep . It appears now it is only half sweep. This machine does not have a tac/ speedometer , it just has the gauge set with hour meter , and warning light set above . I tried to upload a video of the gauges but I for some reason can’t upload . Will attempt
To upload .
To upload .
Nige
Senior Member
You can only upload photos. To upload a video you have to host it somewhere else first then link it in a post on here.
Whether the SERV CODE icon disappears or not after the boot-up sequence will be key to how the diagnosis moves forward.
Nige
Senior Member
See there's the thing. If the gauges sweep when the key is turned on, even if it's not full scale, there isn't likely to be much wrong with the gauge module.
Nige
Senior Member
See if you can find twisted pair of wires going to that module, check the connection, put the ohmmeter across them and measure resistance should be 60 ohm. If it is 120 ohm - you have problems with terminating resistor.
Don’t shove multimeter probes in to female sockets if the connector - just touch them.
Don’t shove multimeter probes in to female sockets if the connector - just touch them.
Yes. And they do go out, or get bad connection. It should look like a two wire connector that plugs in to wiring harness. Nige should help you with locations.
But then again - usually they create more mayhem than one component malfunctioning. But they make network do weird stuff.