alright guys, ive got a d5n with a 3126 that the other morning decided to not crank. got power in cab but n o crank. no power at signal wire on starter solenoid. can jump from hot to signal wire and start. ran wire from keyswitxh to the wire on starter solenoind and can start it. this tells me something between the two is broke. well looked on schematic and found relay. power on one side and not the other while trying to start, ok, i replaced relay. still no start. put new keyswitch in just to be sure and same result. the only thing i can think of is that one of the 2 small wires that go to start relay to close it when starting are broke or the engine ecm, which sends power to the rely, is going crazy. am i missing something or do i have it about narrowed down?
You should try to post serial number when posting a question, it helps to look up info on your particular machine
AKD1933 thanks!
By the way, no active or logged codes and if the 2 wires i reffered to earlier were the problem i should be getting a code. UGGGHHHH!!! i'm bout to pull my hair out! ive got to be missing something simple... maybe signal wire from keyswitch. customer said never had a problem like this till now.
No expert on your machine, but understand circuitry. No offence but I'm going to go with simplistic troubleshooting, just in case There are at least 4 terminals on a SPST relay. Two of the terminals go to the coil and two go to the contacts. When the key is turned to start you get power on one side the relay coil which should pull the contacts in. The other side of the relay coil goes to ground. Having power on one side while cranking is correct most times, no voltage should be seen on other side. There should be power on one side of the contacts prior with the ignition on but not started. When the key is turned and power is applied to the coil side the relay contacts are pulled in and power is sent to the starter solenoid. The computer can make the connections from input from the key switch and other sensors but the basic relay works as mentioned above. Which post have power and which do not?
Your starter relay gets main power across a bus bar from the main power relay. If you look on this diagram the main power relay is #10, the starter relay is #6, the bus bar is #7. The RH terminal of the starter relay should be live with the Master Switch on. The wire connected to the LH terminal of starter relay is the 308 White wire that takes power to the starter motor. The curved wire going up the LH side of the box marked #2 should have 2 wires in it, 306 Green and K972 Brown. Those 2 both come to the start relay out of the engine control (Pins 10 & 67 respectively on connector J1). At the engine control you should also have a wire 307 Orange (pin 64 on connector J1) that comes from the key switch and should be live when you turn the key switch to the "Start" position. Is it..?
Ive got power on the right side of the relay which comes straight from main relay. while key is turned to crank i have no power on the white wire on the left side of the relay. Yes i am getting power from the orange wire on the key switch while cranking.
Do you have power and ground at connector to relay when cranking, is brake release switch on?
OW, this relay is powered and grounded from the engine control, not to machine frame ground. These things (ECM's) do all sorts of weird things, so I wouldn't take it as read that either one of the start relay connections will actually show as being grounded whether the machine power is on or off. The schematic doesn't even list them as "Start Relay +" and "Start Relay -", they're both just tabbed as "Start Relay".
OW has a good point about the brake switch, and possibly we could also mentiond here the transmission control. Either of those 2 in the wrong position (or their respective sensors telling the engine control they are in the wrong position) will not allow the engine to start. You will not have power on the large white wire coming from the LH terminal of relay #6 unless the relay is actually pulled in and the engine is cranking from the key switch. The relay is pulled in by a circuit in the 2 smaller wires (Ref #2 in the diagram above) and they come from the engine electronic control. When you say you are getting power on the orange wire while cranking do you mean wire 307 Orange measured at Pin 64 of connector J1 at the engine control (diagram below) with the key switch in the start position..? I think connector J1 is the one on the left of the diagram below, but I wouldn't swear to it. Either way it's not likely that there is a 307 Orange wire connected to pin 64 of both connectors and the wiring harness plugs are marked on the back with the pin numbers.
On my D6N everything lights up to start ,but won't turn over sometimes.Try holding the switch over to start and pull the brake switch on and off and see if it will turn over.Anyway the park break switch is getting bad on my 6N or it needs cleaned.Usually does it if it sets around in wet weather for a while.Good luck
Come to think of it, you're saying there are no Codes on it. If the park brake switch signal at the ECM was "Off" then there wouldn't be a Code, because "Off" is an acceptable status for the parking brake switch.
WOOOHOOO!!! figured it out! orange wire from key switch to engine ecm was broke some where in the harness. ran a new wire and now we go broom broom!!! This should not have been a major issue for me. one lesson learned; trying to hurry and make good impression for new customer plus panicked troubleshooting = bad diagnosis. came back a few days later for round two with my head in a better place and didnt have much of a problem. moral of the story... when troubleshooting DONT GET EXCITED!!! thanks for all the input guys!
Sometimes stepping back and starting fresh can make a world of difference. Need to think about where power starts and check it out one point at a time. The nice thing about having a good wiring diagram like most of Cat's is you can follow it one connection or plug from start to finish. Then there are the ones where problem only happens once ever month or so, have a problem like that right now on a 769D that "thinks" the transmission is over heating. It's set off the alarm twice since last fall each time as soon as it comes to the shop for me to check problem goes away!
Not some time close to the end of the shift maybe...? The number of machines that have problems round about that time still staggers me ..............
Not this one and if it did we are under orders from way up in management not to work any overtime. Just wish I knew why they die in the muddiest or most in the way place for the rest of the operation? I try telling operators to never shut of a machine for break time in a place that will cause a major problem it it fails to start after break. Very seldom does one fail to start up again but once or twice a year when one does fail it seems to be in the worse place possible.
Nothing to do with overtime. I was thinking more of an operator who wanted to goof off for the last hour or so of a shift. No better way than to experience an obscure electrical fault .....
This one decided not to start right after the customer had lit a bunch of brush piles and one was about 100 feet from where this dozer decided to go crazy at. luckily i showed up shortly after it happened and jumped across relay and got him going. he said he had an hours worth of work to take care of and he would let me have it. well 4 hours later he shut it down after he pushed a fire break cause his fires was bought to jump across to some timberland. crazy where some of these things happen!
Oh! Like the pit loader operator who finds that big stone that will plug the primary crusher for about an hour? "Gee I never saw that one, must have been under those fine stones I was loading!"
We've had a rash of operators lately calling for fuel at around 5:00AM (just about the time the fuel truck's heading to the farm to refill his tank ready for the next shift) when probably the previous evening about 8-9:00PM they refused fuel "because they had over 80%" - you can't go through 80% of a tank in 8 hours no matter how much you burn. What we do now is to take the operator's name, badge number, and his reported fuel % if he refuses fuel when the truck passes by, then if he mysteriously is out of go juice close to end of shift he gets a "Come to Jesus" talk from the Ops Superintendent .............