jonstine
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- Austin, TX
I have looked through the threads for the last 2-3 days, but cannot find what I need. I'm having a lot of electrical issues, and could use some help from you gurus out there.
I have a 1986 M1028 that was rather poorly converted to 12V by someone at some point prior to me owning it. Batteries are 800/1000 CCA/CA, wired in parallel, and about 6 months old. It was a US Army truck that served double duty as a Border Patrol vehicle for a while. There are snipped wires and empty bolt holes all over the thing where I assume the BP had lights or misc accessories that were stripped off unceremoniously when it was time to auction it off. The end result is a rather unclear picture of what the electronics and wiring should truly look like. It does not match any of the TMs exactly because it's been converted to 12V, and it's been bastardized.
Here's the background: I bought it about 2 months ago. Worked fine for about 2 weeks, and the alternator quit working. Replaced the belts and a new Oreilly 01-0136 (DL7157 equivalent) as they were the only one that had anything in stock. Worked fine for about a week, and the truck wouldn't start. Turns out the starter was also bad. Replaced that with a Powermaster 9052. At the same time, I upgraded all of my power cables to 2/0 HD lug versions. Replaced these cables - front to rear parallel battery, front ground to frame, front ground to engine, front positive to starter, front positive to terminal above the glow plug solenoid on the firewall (this was a 2 AWG cable). Worked fine for another week. All power came to screeching trickle while driving one night, was barely able to get home from 5 mi away, headlights were barely putting any light out. Checked all grounds, connections, etc for tightness. Everything appears to be good. Have been fiddling with it for the last 2 weeks trying to get resolved.
Here are the symptoms: When sitting idle with key out, the batteries will hold Voltage overnight. If I turn key to first position, batteries will hold voltage with a very minor drop, like 0.01-0.03 over a minute or two. Once I turn to the On position, the voltage drops like a rock, at least 0.5-1.0 over a 10 second period, and it will keep dropping to 7.0-8.0V. No burning or smoke, and I have hand checked all the wires I can reach, nothing is hot. If I hook up a starter battery, the voltage will push up to almost 13.0 V, but as soon as I turn to the On position, it again plummets even with the additional starter battery charging the parallel batteries.
Yesterday morning, I charged up the batteries and they cranked right over in the morning. I took my boys to school (about 12 mi roundtrip), ran to get a tank full of diesel (about another 3mi), and turned off the truck at the pump. Had been running at 55MPH for at least 15 mi or 20-25 minutes including the school dropoff. When I went to start it, it just clicked. Literally no juice. Thankfully a guy in another diesel cruised over when he saw my hood up. We connected cables, and had to let it sit for almost 4 minutes before it had enough juice to crank. When it did the guy saif his voltmeter dropped to 0V when my truck was starting, meaning it consumed all of his available power for a split second. Drove it home, and it's been in the garage for the last 24+ hrs. Barely takes a charge, even with the charger on it. Voltage still drops like a rock when in On position.
Still with me? The main question I have is, with a converted 12V system, do I still have to use an isolated ground alternator, or can the DL7157 be my singular alternator? If so, do I need to do anything different, like disconnect the ground wire from the alternator to the engine block? Also, there were a couple of small wires that were connected directly to the original starter that I did not realize were there until I bench pressed the starter down from the engine area. One of them broke the ring terminal off, and I was able to disconnect the other two. All three were connected to the power terminal on the starter. Not sure what they are for, but I can get pictures if it would help. I do know that one of them must be connected to 12V + in order for the starter to crank (no, it's not the actual starter positive feed, that is a big 2/0 that I ran straight to the front positive).
Before you guys all yell at me to check my grounds, I have, multiple times. I'm not saying I can rule them out with 100% confidence, but they are all new and in good shape, have good connectivity, etc. Still, if it's a specific ground, or specific area, by all means I am open to suggestions and troubleshooting steps.
My gut tells me that something is shorting out when the key goes to On. My lack of experience troubleshooting CUCV electrical systems tells me that I am in way over my head on this issue. Any help would be appreciated.
Thanks!
I have a 1986 M1028 that was rather poorly converted to 12V by someone at some point prior to me owning it. Batteries are 800/1000 CCA/CA, wired in parallel, and about 6 months old. It was a US Army truck that served double duty as a Border Patrol vehicle for a while. There are snipped wires and empty bolt holes all over the thing where I assume the BP had lights or misc accessories that were stripped off unceremoniously when it was time to auction it off. The end result is a rather unclear picture of what the electronics and wiring should truly look like. It does not match any of the TMs exactly because it's been converted to 12V, and it's been bastardized.
Here's the background: I bought it about 2 months ago. Worked fine for about 2 weeks, and the alternator quit working. Replaced the belts and a new Oreilly 01-0136 (DL7157 equivalent) as they were the only one that had anything in stock. Worked fine for about a week, and the truck wouldn't start. Turns out the starter was also bad. Replaced that with a Powermaster 9052. At the same time, I upgraded all of my power cables to 2/0 HD lug versions. Replaced these cables - front to rear parallel battery, front ground to frame, front ground to engine, front positive to starter, front positive to terminal above the glow plug solenoid on the firewall (this was a 2 AWG cable). Worked fine for another week. All power came to screeching trickle while driving one night, was barely able to get home from 5 mi away, headlights were barely putting any light out. Checked all grounds, connections, etc for tightness. Everything appears to be good. Have been fiddling with it for the last 2 weeks trying to get resolved.
Here are the symptoms: When sitting idle with key out, the batteries will hold Voltage overnight. If I turn key to first position, batteries will hold voltage with a very minor drop, like 0.01-0.03 over a minute or two. Once I turn to the On position, the voltage drops like a rock, at least 0.5-1.0 over a 10 second period, and it will keep dropping to 7.0-8.0V. No burning or smoke, and I have hand checked all the wires I can reach, nothing is hot. If I hook up a starter battery, the voltage will push up to almost 13.0 V, but as soon as I turn to the On position, it again plummets even with the additional starter battery charging the parallel batteries.
Yesterday morning, I charged up the batteries and they cranked right over in the morning. I took my boys to school (about 12 mi roundtrip), ran to get a tank full of diesel (about another 3mi), and turned off the truck at the pump. Had been running at 55MPH for at least 15 mi or 20-25 minutes including the school dropoff. When I went to start it, it just clicked. Literally no juice. Thankfully a guy in another diesel cruised over when he saw my hood up. We connected cables, and had to let it sit for almost 4 minutes before it had enough juice to crank. When it did the guy saif his voltmeter dropped to 0V when my truck was starting, meaning it consumed all of his available power for a split second. Drove it home, and it's been in the garage for the last 24+ hrs. Barely takes a charge, even with the charger on it. Voltage still drops like a rock when in On position.
Still with me? The main question I have is, with a converted 12V system, do I still have to use an isolated ground alternator, or can the DL7157 be my singular alternator? If so, do I need to do anything different, like disconnect the ground wire from the alternator to the engine block? Also, there were a couple of small wires that were connected directly to the original starter that I did not realize were there until I bench pressed the starter down from the engine area. One of them broke the ring terminal off, and I was able to disconnect the other two. All three were connected to the power terminal on the starter. Not sure what they are for, but I can get pictures if it would help. I do know that one of them must be connected to 12V + in order for the starter to crank (no, it's not the actual starter positive feed, that is a big 2/0 that I ran straight to the front positive).
Before you guys all yell at me to check my grounds, I have, multiple times. I'm not saying I can rule them out with 100% confidence, but they are all new and in good shape, have good connectivity, etc. Still, if it's a specific ground, or specific area, by all means I am open to suggestions and troubleshooting steps.
My gut tells me that something is shorting out when the key goes to On. My lack of experience troubleshooting CUCV electrical systems tells me that I am in way over my head on this issue. Any help would be appreciated.
Thanks!
