Deere Mack Posted November 19, 2019 Share Posted November 19, 2019 I've got a voltmeter pegging out. I've checked all the grounds, replaced the meter itself with no luck. It's charging normal, everything checks out with my hand held. I'm sure its grounding out somewhere but I was hopping someone might point me in the right direction. Thanks in advance! Quote Link to comment Share on other sites More sharing options...
fjh Posted November 19, 2019 Share Posted November 19, 2019 Did you check the boys at the alt it maybe an actual problem! You should confirm Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted November 19, 2019 Share Posted November 19, 2019 (edited) If it was grounding it would be bottoming out, so I assume pegging is top of meter scale??? Alternators produce AC and diodes turn it to DC. Test the system and dial between AC and DC on your meter. You may have a failing rectifier in your alternator allowing Alternating Current to be produced. Edited November 19, 2019 by Mack Technician Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 19, 2019 Author Share Posted November 19, 2019 I'll check it out again when it gets back this evening. It's been like that since I got it earlier this year. The only problem I've had is one time it "glitched" and the lighting bolt and ABS light came on with loss of engine power for split second. Then it cleared up almost instantly but I honestly feel like it hasn't run the same since. Mack said it did have a stored code, cant remember what it was. but basically something had shorted out somewhere, but unless the code was active it would be hard to pin down. Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted November 19, 2019 Share Posted November 19, 2019 (edited) Full disclosure? You’d have cooked batteries or the alternator would have probably given up the ghost by now if my scenario was correct. I’ll check my diagram when I get home and see what you need to be reading. There’s the distinct possibility that our previous owner, Mr.Chucklehead, took your dash apart, drank a 40 of Molson Ice, and relocated gauges to holes they aren’t suppose to be in????? Maybe? Crackpipe theory? How many empty holes do you see in the dash? Any other gauges not reading with a sound mind? Voltage gauge has a pretty easy job, he’s not a rocket scientist. Hard to blame the dash since he’s only reading a predetermined vital. Can’t picture the dash producing a magnified voltage. Edited November 19, 2019 by Mack Technician 1 Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 20, 2019 Author Share Posted November 20, 2019 (edited) 10 hours ago, Mack Technician said: Full disclosure? You’d have cooked batteries or the alternator would have probably given up the ghost by now if my scenario was correct. I’ll check my diagram when I get home and see what you need to be reading. There’s the distinct possibility that our previous owner, Mr.Chucklehead, took your dash apart, drank a 40 of Molson Ice, and relocated gauges to holes they aren’t suppose to be in????? Maybe? Crackpipe theory? How many empty holes do you see in the dash? Any other gauges not reading with a sound mind? Voltage gauge has a pretty easy job, he’s not a rocket scientist. Hard to blame the dash since he’s only reading a predetermined vital. Can’t picture the dash producing a magnified voltage. The possibilities of the previous owner are endless. For example, he welded my gate pins in place. I mean come on now! Had to carry it back to mack today because they turned off my engine oil temp gauge from the previous update 🤦♂️, so I had them to look at while it was there. He said it had to be the in the dash because everything else checks out. All other gauges work fine except my fuel gauge, it can be squirrely at times but I'm sure that's probably the sending unit. I've attached a photo showing my arrangement with the voltmeter circled in red. If it's right or not I couldn't tell you. Edited November 20, 2019 by Deere Mack Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted November 20, 2019 Share Posted November 20, 2019 Feel you pain brother... that no-save-customer data thing was screwy. Good news is we scored a boxed dashboard off eBay a year ago. They’re there. Be aware.....Mack made a bunch of bad CV dashboards back in the day. They listed a serial number and said “every dashboard older than blah blah blah is destine to fail”. I was cautiously watching and waiting for some of these “throw always” to be dug out of a PDC dumpster to appear online. I haven’t seen any for sale which fell into the “junk” vintage. When it comes time to buy ask for the production code off the dashboard which is for sale. You can cross the number before buying. Quote Link to comment Share on other sites More sharing options...
mrgumby Posted November 20, 2019 Share Posted November 20, 2019 What does it read if you just turn the key on without the truck running Does it still peg the meter 1 Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 20, 2019 Author Share Posted November 20, 2019 47 minutes ago, mrgumby said: What does it read if you just turn the key on without the truck running Does it still peg the meter Gives same reading, almost pegged out Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted November 20, 2019 Share Posted November 20, 2019 What does You fluke meter say when your testing at the battery(s) and at alternator? Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted November 20, 2019 Share Posted November 20, 2019 Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted November 20, 2019 Share Posted November 20, 2019 Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted November 20, 2019 Share Posted November 20, 2019 Third opinion agrees with your placement. I'd test battery, alternator, power into dash and power at gauge pegs. These dashes had ground issues, but that wouldn't cause what your seeing, it would be a drop-out issue. Quote Link to comment Share on other sites More sharing options...
ivanuke Posted November 20, 2019 Share Posted November 20, 2019 (edited) Try removing the dash and see if you can get your meter leads to touch Pins 29 for power and pin 35 for ground (cant remember if the wires had boots or if the crimp is exposed enough to get leads on it. or maybe get sharp leads to poke the wire). If you have 14 volts I would get another dash. Pins 29 and 35 are somewhat close together, just be careful they don't touch when checking voltage. Edited November 20, 2019 by ivanuke 2 Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 21, 2019 Author Share Posted November 21, 2019 On 11/20/2019 at 1:51 PM, ivanuke said: Try removing the dash and see if you can get your meter leads to touch Pins 29 for power and pin 35 for ground (cant remember if the wires had boots or if the crimp is exposed enough to get leads on it. or maybe get sharp leads to poke the wire). If you have 14 volts I would get another dash. Pins 29 and 35 are somewhat close together, just be careful they don't touch when checking voltage. Thank you for that information! I'll check that first chance I get. Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 21, 2019 Author Share Posted November 21, 2019 On 11/20/2019 at 5:00 AM, Mack Technician said: What does You fluke meter say when your testing at the battery(s) and at alternator? I appreciate the help! I'm reading 14v at alternator. I've got bigger problems now. Truck shut down today on job site. ABS and traction control light are on with lighting bolt, 6-4 code. Everything seem to be getting power, it cranks over fine but will not start. I've read a few forums about this, it doesn't look good. I'm pretty sure I smelt electrical smoke when it happened. 1 Quote Link to comment Share on other sites More sharing options...
ivanuke Posted November 22, 2019 Share Posted November 22, 2019 (edited) Sorry to hear that, if you have Code 6-4 thats loss of communication to an ECU. Attached are the troubleshooting steps from the V-Mac III manual for this code, go through these tests and it may help you find the fault, there is a paragraph in there if you lose both communication lines the engine wont start. Let us know what you find! CV713_6-4_Troubleshooting_Guide.pdf Edited November 22, 2019 by ivanuke Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 22, 2019 Author Share Posted November 22, 2019 1 hour ago, ivanuke said: Sorry to hear that, if you have Code 6-4 thats loss of communication to an ECU. Attached are the troubleshooting steps from the V-Mac III manual for this code, go through these tests and it may help you find the fault, there is a paragraph in there if you lose both communication lines the engine wont start. Let us know what you find! CV713_6-4_Troubleshooting_Guide.pdf 2.39 MB · 1 download I can't thank you enough. I'll let you know what I find out. Let the fun begin! 1 Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 23, 2019 Author Share Posted November 23, 2019 Does anyone happen to have the diagram for the fuse panel on the firewall. Mine's smudged up and I cant read it. Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 23, 2019 Author Share Posted November 23, 2019 (edited) One of the few fuse descriptions I can make out from my panel is ECU and its blown. Replaced it and immediately blew again. I've heard of the firewall fuse panels giving trouble. Think its possible or it's the other. I haven't had time for a full diagnostic test due to rain. Gota brief break and found this. Edited November 23, 2019 by Deere Mack Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 24, 2019 Author Share Posted November 24, 2019 I'm not electrical engineer but this doesn't look right. Quote Link to comment Share on other sites More sharing options...
ivanuke Posted November 24, 2019 Share Posted November 24, 2019 (edited) I was just about to message you, I spent some time looking through the schematics. If you disconnect the J2 line and the fuse keeps blowing you have a short in the harness. If it doesn't blow and it blows when you have J2 connected, your ECU is probably bad, but now it looks like you have pretty good damage on both sides. If you determine your ECU is bad I'll offer to buy from you, I want to take a stab at repairing one. If i were you, I would clean that connector as good as I could, and make sure there is no visible shorts (use your multimeter on ohm setting to make sure theres no short from pin to pin) and if it looks good, put another fuse back in and see if it pops (which it shouldnt if all pins were good during the ohm check) This would help determine if it was the harness or the ECU, the connector looks pretty destroyed, hopefully its salvagable. Not sure if mack sells connector parts. Edited November 24, 2019 by ivanuke Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 24, 2019 Author Share Posted November 24, 2019 (edited) 23 minutes ago, ivanuke said: I was just about to message you, I spent some time looking through the schematics. If you disconnect the J2 line and the fuse keeps blowing you have a short in the harness. If it doesn't blow and it blows when you have J2 connected, your ECU is probably bad, but now it looks like you have pretty good damage on both sides. If you determine your ECU is bad I'll offer to buy from you, I want to take a stab at repairing one. If i were you, I would clean that connector as good as I could, and make sure there is no visible shorts (use your multimeter on ohm setting to make sure theres no short from pin to pin) and if it looks good, put another fuse back in and see if it pops (which it shouldnt if all pins were good during the ohm check) This would help determine if it was the harness or the ECU It had leaks from the coolant tanks when I got it. I replaced those and the sensor etc. I'm thinking the coolant leaked down on it and caused the corrosion and short, especially since all the trouble is at the bottom. I'll take a closer look tomorrow and check the pins out. The pin connector/harness looked to be toast. Edited November 24, 2019 by Deere Mack Quote Link to comment Share on other sites More sharing options...
Deere Mack Posted November 24, 2019 Author Share Posted November 24, 2019 2 hours ago, ivanuke said: I was just about to message you, I spent some time looking through the schematics. If you disconnect the J2 line and the fuse keeps blowing you have a short in the harness. If it doesn't blow and it blows when you have J2 connected, your ECU is probably bad, but now it looks like you have pretty good damage on both sides. If you determine your ECU is bad I'll offer to buy from you, I want to take a stab at repairing one. If i were you, I would clean that connector as good as I could, and make sure there is no visible shorts (use your multimeter on ohm setting to make sure theres no short from pin to pin) and if it looks good, put another fuse back in and see if it pops (which it shouldnt if all pins were good during the ohm check) This would help determine if it was the harness or the ECU, the connector looks pretty destroyed, hopefully its salvagable. Not sure if mack sells connector parts. I went back out to the truck. I cleaned the connections the best I could. The harness connector and the pined connection at the ECU are both toast. Managed to get it running long enough to dump my load off. It kept blowing the fuse and when I would unhook the bottom connector on the ECU gas/pressure would escape. Going back in the morning with the lowboy truck and hopefully get it running long enough to load it up. Quote Link to comment Share on other sites More sharing options...
ivanuke Posted November 25, 2019 Share Posted November 25, 2019 (edited) It looks like Pins 10, 22, and 24 are the culprits. Pins 10 and 22 are 12v+ and 24 is ground. If everything else works fine in the truck, like your headlights and windshield wiper, I think the ECU is what caused the problem, an internal failure Im thinking. If you're looking at the harness connector, pin 1 is upper right hand side, count down. Top half has 4 rows bottom half has 3 rows. Are there any other fuses that are blown? If so please list them here. Also are you saying if you connect it back you can turn on the truck by replacing the fuse, but itll blow shortly after? Not an immediate blow? Edited November 25, 2019 by ivanuke Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.