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Discussion Starter · #1 ·
So I bought this truck all seemed well until I got at home the battery died the first night so I took the battery and got it tested and it turned out that it was bad. So I slapped a new battery in and thought all would be good. It was not! So I grabbed my voltmeter and checked the battery while the truck was running and found that the alternator was not charging probably due to the faulty external voltage regulator that was wired in so I pulled that out and converted it back to the stock wiring then changed out the faulty ECU for a brand new one Still nothing I changed out the CPS sensor along with the ASD relay all to no avail the ecu still will not ground out pin 87 on the ASD relay and still no tech in the cab I checked the wiring from the CPS all which is good and working the ECU is getting a signal from the CPS. The alt will charge about .75v when I jump the asd but not much more I also deleted the fusible links. I’m completely stumped please help
 

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So I bought this truck all seemed well until I got at home the battery died the first night so I took the battery and got it tested and it turned out that it was bad. So I slapped a new battery in and thought all would be good. It was not! So I grabbed my voltmeter and checked the battery while the truck was running and found that the alternator was not charging probably due to the faulty external voltage regulator that was wired in so I pulled that out and converted it back to the stock wiring then changed out the faulty ECU for a brand new one Still nothing I changed out the CPS sensor along with the ASD relay all to no avail the ecu still will not ground out pin 87 on the ASD relay and still no tech in the cab I checked the wiring from the CPS all which is good and working the ECU is getting a signal from the CPS. The alt will charge about .75v when I jump the asd but not much more I also deleted the fusible links. I’m completely stumped please help
There are many posts on this, so I'll just get to my fix. Same as you, alt wouldn't charge. I tried many things, until I got to the grounds. There is a big cable on the alt that goes directly to the front flat part of the engine. It's pretty short--maybe 8 to 12 inches. Try taking the bolt out of the engine side of this cable and clean and buff the mounting point and the end of the cable. I bought a star washer to dig into the mounting plate, and I never had the charging problem again.
 

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The best and cheapest fix in the long run is to either use the external regulator or a 1 wire alternator. I use the 1 wire from PAPERFORMANCE on my Fummins and not a problem in 5 1/2 years. I use the adjustable external regulator on my Blazer 12v and no problems for 3 years now.
 
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Discussion Starter · #4 ·
There are many posts on this, so I'll just get to my fix. Same as you, alt wouldn't charge. I tried many things, until I got to the grounds. There is a big cable on the alt that goes directly to the front flat part of the engine. It's pretty short--maybe 8 to 12 inches. Try taking the bolt out of the engine side of this cable and clean and buff the mounting point and the end of the cable. I bought a star washer to dig into the mounting plate, and I never had the charging problem again.
good information unfortunately I already did this
 

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good information unfortunately I already did this

There's alot of info on all the 1st Gens electrical problems on the Forum and anytime you can delete something from the troublesome ECM you'll be happier.
 

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What little that ECM does can be done by other ways it's there scattered all over the Forum and some of us older Members heads.
 
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