JA101 Posted June 11 Share Posted June 11 Hello, On my Mack, the diff lock switch lights have always acted up. One switch had no indicator light, and the other is very dim, but works. I removed the switch with the broken light, dismantled it, cleaned it up, and soldered in a replacement red LED, figuring that was the problem. I replaced the switch, and no light. So I swapped plugs, and now I have a bright indicator light on that switch, and none on the one that was dim but working. So it seems like wiring connector #1 has a fault somewhere down the line. From my understanding on working on other vehicles with similar switches, there is a relay somewhere that sends power to the switch indicator telling it to turn on when engaged. But... where is that relay? And is that the problem? Macks are very hard to find diagrams for, I can't find anything useful to help find it. I am guessing it is either behind the dash or in that relay panel on the passenger side, but again, nothing can be found online. Anyone encounter this before? Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/ Share on other sites More sharing options...
Joey Mack Posted June 11 Share Posted June 11 Are the wires all white? Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553560 Share on other sites More sharing options...
JA101 Posted June 12 Author Share Posted June 12 Yes, all white. Now that I think of it, how exactly does this light get its signal? Is it a simple switch on the differential? I wonder if I am just hearing it try to engage but it never actually does. Its going to the mechanics pretty soon so I can have it checked. Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553606 Share on other sites More sharing options...
Joey Mack Posted June 12 Share Posted June 12 Ok. The wire code is printed on the wire. It tells you where the wire goes its size and pin number in the ECU plug. Can you post the numbers on each wire? Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553607 Share on other sites More sharing options...
JA101 Posted June 13 Author Share Posted June 13 Ill go check it out and get back Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553668 Share on other sites More sharing options...
Joey Mack Posted June 13 Share Posted June 13 Ok. If this Mack has the Volvo frame, then there should be a bank if electric over air celenoids on the cross member behind the cab, possibly on the frame. There is where the air is sent to the lockers, Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553669 Share on other sites More sharing options...
JA101 Posted June 13 Author Share Posted June 13 Im not sure, I will go check. I do know it was affected by the frame issue they were having, so its a new frame. I see things printed on the wires, such as UJ1-3-D.8. Is that what you mean? Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553672 Share on other sites More sharing options...
JA101 Posted June 13 Author Share Posted June 13 I dont believe there are those solenoids behind the cab. I do see a couple solenoid type things closer to the mid point of the frame by the side rail. Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553673 Share on other sites More sharing options...
Joey Mack Posted June 13 Share Posted June 13 It should be VJ1-3-0.8. So that is vehicle ECU plug J-1/ pin 3/. Wire size ( not relevant) .8.... The code stays the same on the whole circuit, this can be used to trace wires and use a DVOM to check continuity and such. This way you dont have to pull all the wires out, just look for that code.. i gave you this info in case you have to go deeper than the basic checks.. jojo Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553676 Share on other sites More sharing options...
JA101 Posted June 13 Author Share Posted June 13 Oh okay, thank you for the info. Assuming continuity is okay, would that point to an ECM issue, or is there a switch on the differential that could be bad? Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553678 Share on other sites More sharing options...
Joey Mack Posted June 13 Share Posted June 13 I doubt ECM.. I would look for damaged wires on the frame and not sure about wires on the diff. Memory escapes me right now.. Quote Link to comment https://www.bigmacktrucks.com/topic/74258-2004-mack-cv713-diff-lock-switch-help/#findComment-553679 Share on other sites More sharing options...
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