Lost tach, speedo and won't charge..HELP! - Diesel Bombers



12 Valve 2nd Gen Dodge Cummins 94-98 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with P7100 Injection Pumps

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Old 07-16-2012, 09:32 AM
Diesel Fan
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Default Lost tach, speedo and won't charge..HELP!

I have been chasing a no tach issue for some time now. A couple of weeks ago I also lost the speedometer. I went on vacation last week and the day before we left, the trans on my Government Motors peice of crap went out so I had to pull the boat with the Dodge knowing that there were a few electrical issues. I have new batteries in it and have only driven it a few times getting ready for the paint booth, so I found out the hard way that it wasn't charging. I have checked all fuses. I did find a voltage draw on fuse 10 in the fuse box under the hood. My Haynes manual tells me this is the circuit for the tach and alternator. I disconnected the alternator wires and still have a voltage draw. I don't think its a bad alternator. I have removed the instument cluster and cleaned all the connections. There is no visible sign of wire damage from the outside of the loom. Any suggestions are much appreciated.
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Old 07-16-2012, 09:07 PM
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The Crank Position Sensor on the harmonic balancer has caused some odd electrical things like what you're describing. Check the condition of the wire running to it.
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Old 07-16-2012, 10:29 PM
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I agree with Dave, check your CPS and the wires running to it. IIRC they have to be gapped similar to a spark plug, that is also something to look into.
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Old 07-16-2012, 11:04 PM
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Default no charge

just fixed mine a couple days ago, was the wiring going to the cps, my wirring was bad on front top side of engine where it goes through holder. found problem by having some one in cab while i was outside wiggling and moving wires around and they would tell me when tach was working or not, you can also tell by the motor tone when alt is charging then stops charging while you are moving wires around.
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Old 07-17-2012, 06:24 PM
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Thanks for the suggestions. I beleive my problem is a little deeper. I do not have power to the sensor and I can not find any wire damage. I tested it at the connector right in front of the valve cover. I have pulled and checked the connectors on the ecm as well. They all look ok. I also learned that the 10 amp fuse in my power dist. box is labeled as the fuel pump fuse. Not the gauges. There is no load on this circuit with the key on!?!?!?!? It seems to run and everything works with it out. I am starting to suspect an ignition switch problem. I will work on it more tonight.
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Old 07-19-2012, 07:48 PM
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Well it looks like I have a bad ECM/PCM. No 5vdc power our of the PCM on pin 17 of the wiring harness. I checked the intake air sensor as well and have only .8 volts. Should be 5 as well. Any suggestions on a good outlet for a PCM?
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Old 07-19-2012, 08:43 PM
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Man, that's rough. I'm not sure of anywhere in particular that sells PCMs. Maybe try asking for a quote in the sponsors section.
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Old 07-20-2012, 03:54 PM
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just read your post i bought my dodge for 500 dollars for the same reason no speedo no overdrive and no charging. pcm fixed it. picked it up at the dealer i work at for $149. next day i had it rolling, good news is previous owner installed a cps, alternator and a batt. days before i bought while trying to fix the problem. sold the truck with 420k on the clock and it still ran fantastic
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Old 07-20-2012, 04:48 PM
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Asked for price quotes on this site. Prices caming back at nearly $400. Dixierebel, do you work for a dodge dealership? That price on a PCM seems really cheap. I found a used one on ebay for 150, but I wouldn't trust it. Removed, cleaned and reconnected all of my grounds today. Still no power to the engine control sensors. I definitely need a PCM.
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Old 07-22-2012, 02:09 AM
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Sounds to me like the voltage regulator is shot, that's what happened to mine and it sounds like the same symptoms mine had, you can wire one externally, its pretty easy if your mechanically inclined
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