Good morning everyone. Ok so I boughy a 99 24v 2500 at an auction not knowing it had electrical issues because whoever put it in the auction put little squares of electrical tape over the idiot lights in the instrument cluster unbeknownst to me. For the life of me I cannot figure out why the truck is not charging. When I start it, the voltage meeter in the dash reads about 12v. I've confirmed this with a volt meter, it reads 12.34v at the batteries as well as the back of the alternator. After about 30sec the check engine light comes on and the volt meter drops to below 8v. At that point I check to see what the alternator is putting out and it still reads 12.34v. My thought was maybe the grid heater is bad, so to check that I, disconnect it and start it back up again. Same result, same reading on the voltmeter. Mind you I have been chasing this problem for months. I've installed both a new PCM and an ECM thinking they might have gone bad. Still the same issue. I've had my scan tool hooked up to it many times and the only code it reading is P0222(throttle/pedal position sensor B circuit low input). I'm not that great with electrical but I don't think that code would cause this issue I'm having. I have checked and cleaned all grounds, replaced all the fuses, relays, alternator, installed new batteries, and had the instrument cluster repaired, replaced every single sensor on the truck, But to no avail nothing I've done has fixed the problem. I need help bad otherwise I'm going to sell the truck. At this point I've put way to much money, time,and effort into this truck to sell it but I'm at my wit's end with this POS. Please help someone!
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Disappearing Voltage, not charging
- Thread starter MNeuharth
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No I have not replaced that. What would that do?
GAmes
TDR MEMBER
The PCM changes the charge rate depending on battery voltage. When the sensor fails it can cause the alternator not to charge, and in my case caused the PCM to fail. I installed a new PCM, it didn't work. I tested the temp sensor per the FSM, it was bad. I replaced it and the new PCM started working. A simple ohm test will rule it in or out.
Is there any way I can bypass that sensor?
B.G. Smith
TDR MEMBER
12.3 is not an indication that thee alternator is working. If working and with engine running it should show 13.8 to 14.4 volts. Check the big fusible link at the pdc, I think it is 125 amps. Also the crank shaft position sensor, I think it may send signal to pcm to energize alternator but if it is bad the tach may not work? bg
Test sensor here, post #10
https://www.turbodieselregister.com/threads/hot-battery-on-rh-side.266917/#post-2592310
https://www.turbodieselregister.com/threads/hot-battery-on-rh-side.266917/#post-2592310
Correct, the tach will not work with a bad crank sensor.
The book says the sensor should show 9k to 11k ohms. My ohm meter set on the 2000k setting is reading 6-7k. I think the sensor is bad. What say you.
I'm on my way to get the new sensor and a new fuse for the alternator even though it's not busted from what I can see. I'll check back in with you guys when I install the new parts. Be about an hour.
Ok so I installed a new battery temperature sensor as well as the 140amp alternator fuse. I'm still having the same issue. It still says about 12v on the gauge and my voltmeter says the brand new alternator is putting out the same 12.36v while the truck is running. The volt gauge inside the truck will remain at 12v until I hold the throttle down. Upon applying more throttle, after about 30sec the check engine light comes on as the volt meter drops to below 8v. However my multimeter still says 12.36v at the battery with the engine running and the gauge in the truck indicating 8v. After I shut the truck down, and turn it back on again, the gauge will go back to indicating 12v. Im at a loss for words right now. I need more advice here fellas.
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GAmes
TDR MEMBER
It might be worth the time to wire in an external voltage regulator. It will confirm if the alternator is really charging (it appears it is not with only 12 volts) and will bypass most of the truck system. If your battery gauge is wired the same as mine it will show charging. I carry a VR with me in case my PCM dies while I'm on the road. It is a BWD Select R400 from one of the parts stores. Wiring directions have been posted several times, so when I had a failure it was a simple process to search the procedure. Mine has 4 connectors. After totally removing the block connector from the alternator and zip tieing it out of the way, F goes to one of the small posts. A ground wire goes to the other small post. (it doesn't matter which one) S goes to a switched hot, I tapped into the hold wire for the FSS. A goes to the large post of the Alternator. I is unused. Pretty hard to screw it up.
Ok so I followed his instructions all the way to the end where I test to see if I have 12v coming out if the alternator by way of checking the back of the pins on the PCM connectors. Set to check voltage my voltmeter reads 0.06volts. so am I to believe that my wiring is bad from the alternator to the PCM? That's kinda what I'm thinking....
It looks like might be headed towards installing an external voltage regulator. This is exactly why I don't want to get rid of my 98 12v. It's just easier to work on. This 99 is a pain in the ass.
Engine running ?
The dark blue wire is the voltage supply to the Generator fields. Meaning this is a positive wire and should have 12V on a meter or light a test light like this when the test light is hooked to battery negative as in the picture. (A meter would be the same with the negative lead) Engine MUST be running, key on engine off does not work for this test.
The dark blue wire is the voltage supply to the Generator fields. Meaning this is a positive wire and should have 12V on a meter or light a test light like this when the test light is hooked to battery negative as in the picture. (A meter would be the same with the negative lead) Engine MUST be running, key on engine off does not work for this test.
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Issue 128 – Digital Version
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Subscribe
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Back Issues
Subscription Status
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