Alternator has burnt off the exciter post for the second time this year, both Denso units and grader less than 2500 hrs old. Voltage was normal after fitment and has probably done 200 hrs on the new alternator. Any help appreciated.
Not particularly talking about your grader, just electrical connections in general. That usually indicates a bad connection. Or maybe I should say a connection that cannot handle the voltage/amperage draw involved.
My Auto Electrician tells me the wiring harness have more than likely rubbed though and shorted the exciter wiring. He suggested that a fuse (5amp) be inserted inline to protect the alternator whilst trying to find the culprit. Apparently Kenworth K200 had similar problems.
2 questions for a kickoff. Machine Serial Number.? What is installed on it electrical-draw wise..? How many lights (halogen, HID, LED.?), comms equipment, grade control, etc, etc..? If it's anything like the 16's the alternator output is borderline if the machine has a ****-pot full of electrical accessories installed on it unless it has the optional high-output alternator installed. Again if it's anything like the larger models one place to go looking is the connections in the main electrical panel behind the circuit breakers.
Looks like it has all the bells and whistles, will be at the machine tomorrow with a new alternator and a check of the messenger may highlight a direction. Caterpillar cannot provide a clear picture of the wiring diagram to help, so back to basics checking.
Electrical Schematic is not a problem. Post a Serial Number and I’ll send you one.
For my own clarity. Are we talking about the output terminal of the alternator?
Update, the exciter wire(green) was exposed in the harness about 18" below the alternator mounts. It had contacted the chassis at some point and grounded to the chassis. Hence a $4000 lesson.
B9D05075 140m 2018 thanks.
Cat Messenger still showing an active fault, alternator not charging. Tested 27.82v running at idle no load , exciter output 12.34v. Does it need the chassis ecm checking for damage?
It won’t be the last harness that gets changed on it, you mark my words. Any Diagnostic Codes showing on the Messenger.? Schematic on the way as soon as I can download one. EDIT: Sent - check your PMs.
Thanks for the updates. Looking forward to hearing a solution.
The alternator puts out a large amount of amps on those machines - I can see some options up to 280 amps. Usually this is far more than is required, but it is configured that way on the assumption that the machine is equipped with all the optional lights (in halogen, because that's the standard type of light), other attachments, etc, etc. The result is that the main alternator cable carries a very high current when the batteries are charging. That can lead to loose/burned cable connections in the back side of the main power receptacle box where the circuit breakers are located. Even if everything it tickety-boo electrically the standard high-output alternators still don't last long on those machines. Our 16Ms had all LED lights and the power requirement was much lower. IIRC we replaced the standard with 110-amp alternators.
Another issue I found was the old leaking breather cap &o’ring. Why in god’s name is it mounted so low and behind the circuit breakers. Blow pass oil dripping out of the console.
Makes sense. Our machine has two alternators for 200 amp total. We have LED lights. No way we needed that. It came with one of the powertrain options that we selected. Being a G model our amp draw is extremely low.
Problem is that on an M there is only space for one alternator.....
Our alternator is a 150 amp unit with an optional 110 amp for the basic machine.
I don't know about a 140M but on a 16M the biggest optional lighting package contains 20 lights. Now if each light is a 75W halogen it would need 60 amps from the alternator just to run the lights. Replace them with LEDs and even for the same total number of lights the current draw drops from 60A to 15A. However the alternator output has to be calculated based on the assumption that the machine will be equipped with halogen lights, That's how they ended up with 200+ amp alternators...........
Yep. That's the situation we are in. 18 LED lights. Cab pre cleaner system which runs an electric fan. Interior fan. Then all the miscellaneous electronics. I'm sure we are way under the 200A output.
Well we had every accessory known to man (and maybe a few that weren't) including a Dispatch system, GPS, 2 comms radios, fire suppression system, operator anti-sleep system, etc, etc, and we found we could esadily get away with a 110A alternator.
So by this statement I take it you are talking about the relay terminal when you say exciter. If so it should only be signalling the alternator charge indicator from that terminal. Is the terminal just a small pin?