I have a cat 312cl and the display was ripped out when a tree came in the cab. It had bare wire showing so im sure something could have shorted it. Anyway I bought a new display and it does not work. I have power from ground (black wire ) 24v and some lower voltages. But I do not have voltage from ground to the red wire, I have tested past the connector and still nothing. I guess my question is would the red wire keep the display from coming on ? If so where does that red wire go? Ser# CAT0312CPCBA02359
You're talking about this one (#4), right.?
Yes That is the one
OK, see the extract below from the electrical schematic. Concentrate on the 3 wires at the toip of the illustration, forget the rest for now. Unplug the 8-pin connector on the left side and measure the voltage between Pins 1 & 2 (red & black) on the machine side. You should have 24v (battery voltage) provided that the battery master switch is in the ON position. Then turn the key switch to the ON position and measure the voltage between Pins 2 & 3 (Pink & Black). Again you should have 24v. It might seem like a random question but is the dome light in the cab working.? If it is not working, was it working before the incident with the tree branch.?
Im not at the machine right now. I was messing with it yesterday. I was able to get 24v from black and pink. Nothing from Black and red. I just bought this machine and the dome light has never worked (bulb I guess). I have test all fuses and all check good. ECM Does have a yellow light (center light) Im assuming it is because the display is not working ....
The reason I asked about the dome light is that it is supplied from the same fuse as the monitor panel. I'll send you an electrical schematic. Keep an eye on your messages.
Thanks that would be helpful . I will check power at the dome light this afternoon. I really appreciate your help.....
I finally had a chance to get back to the machine. I do now have 24v from black to red(turns out the connector pin was bad so I bypassed it) I also have 24v black to pink (key on) looks like two pink wires but only one has power. But I still have no display, The new one doesn't works and the old one doesn't work..... Scratching my head.... sent you 2 pics just showing what im working with and shows the red wire bypass
The second pink wire on Pin 7 of the connector is for the panel lights. It should power up when you put the lights on. If with the key on you have power between both red (unswitched) & pink (switched) wires to black (ground) then there is no problem with the power supply. It's then down to the datalink to the monitor and from what I know it's not possible to test that without an oscilloscope. Coming to the conclusion that you need a good auto-electrician with all the tools.
Makes sense,,,,, Thank You so much for your help. I will let you know if I get this problem solved.........