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02 ram 3500 4X4 manual 6 speed. I bought it in sad shape, wouldn't start. New items are batteries, battery cables, starter, alternator. At this point it would start and run, instrument cluster worked. Still no charging. I tested voltage coming from PCM, blue wire to ground=0. I had checked continuity of green and blue wires to make sure they weren't eedshorted or open. I'm assuming PCM was bad. At this same time I decided I would charge the batteries up. I removed them and charged them. Upon installing them I accidentally shorted black and red together on the passenger side with the driver's side hooked up. Then when I started the truck it ran but no bus appeared and no instruments worked. I installed a refurbished PCM and got 7 volts on the blue wire to ground, still no charging or instrument cluster. I have a cheap obd reader and when I leave it hooked up while running all my gauges work. When I unplug it they stop working. Also getting a 1698 code that keeps coming back.

 

I want to thank all of you for helping this far,I couldn't have done it without you. I did download the service manual but I'm not very good at reading electrical skematics. This is the first post I've ever done so be patient with me, thanks...

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When I shorted mine one time MoparMan suggested I unhook the batteries for a half hour. It solved the problem of the gauges not working  and settled down to where they should be reading. I hope you get it smoothed out.

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Both grounds for the PCM and the one for the OBD plug ground at the passenger side battery.  When you shorted the positive cable to the ground cable power might have gone through the PCM back wards. 

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In my case I shorted the ecm ground to positive. I was so tired from working too much I got things crossed up. It turned out okay though and I hope it does for you also.

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Thanks again, yep it was pin 30/31 no ground, connector doesn't have a lock when closed and worked loose. I taped it up for a short term fix and will replace connector as soon as I find one. Now my instruments work but I'm not charging. I un-plugged alternator blue and green wires, started er up and checked voltage on blue=0, green had ground. I have put a 7.5 amp as described, to protect PCM from an alternator short. I checked it and it's good. I am assuming the PCM is bad???

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13 hours ago, Dumb A said:

Thanks again, yep it was pin 30/31 no ground, connector doesn't have a lock when closed and worked loose. I taped it up for a short term fix and will replace connector as soon as I find one. Now my instruments work but I'm not charging. I un-plugged alternator blue and green wires, started er up and checked voltage on blue=0, green had ground. I have put a 7.5 amp as described, to protect PCM from an alternator short. I checked it and it's good. I am assuming the PCM is bad???

We have two rules around here..... number one, it okay to hijack a thread every once in awhile. Number two, never assume the most expensive items on your truck first. :thumb1:

Edited by JAG1
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I will clean up these ground splices as you've described. I like doing these upgrades as preventive maintenance rather than along side the road (crisis management style). I still don't think the PCM is correct as it's not supplying 12 v on the blue wire to the alternator? 

Hey JAG1, I'm a bit of a dumb A when it comes to posting as I've now posted a total of 4 times... Did I highjack this thread? I'm a little confused when you stated the two rules as maybe I broke both of those rules?

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I posted a minute ago and everything was deleted  on just an edit for spelling. Even Dumb A's post that I quoted. What's with that?

 

 

Basically I made up the rules to make the OP feel welcome, that we aren't the Gestapo.

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  • 4 weeks later...

I did get my charging system working and got my "no bus" fixed as well. The "no bus" was an open ground because one of my connectors by the passenger battery came apart. The charging system was fixed by purchasing a single wire alternator from HEI in Oregon, 288 dollars free shipping. It has been 14.2 at idle or WOT. This is a Bosh alternator and a direct bolt in, no mods. The two control wires are now capped and secured to the upper alternator bracket with a zip tie, in the unlikely event I may want to go back to a stock system. I had gotten a refurbished PCM and it had the same problem as the one I sent in for repair. Rather then arguing with this company in Florida I just decided to go with a one wire alternator ( self regulated) hope this answers your question.

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Posted (edited)

Pretty cool way of handling that problem and thank you for letting us know the solution.

 

 So you are saying 'one wire alternator'.... does that mean just the single heavy charge cable?

 

Being 'self regulated,' does it mean that it can read thru the charge cable as to what the batteries need for charge level?

Edited by JAG1
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9 hours ago, Dumb A said:

I just decided to go with a one wire alternator ( self regulated) hope this answers your question.

 

Just remember that your battery life span will be greatly shortened. The old school voltage regulators like your one wire and the old school Mopar Voltage Regulator does not monitor battery temperature so it really easy to have that alternator boil the electrolytes out of the battery. At least the Mopar Regulator does have some temperature regulation but all depends on the under hood temperature for the voltage supplied. 

 

I would suggest getting back to the PCM if possible. Battery temp sensor does actually does a great job of preventing battery from boiling or loss of electrolyte. 

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Yes JAG1, that's what that means. This is a common system in many vehicles "self regulated alternator" with one wire running to the battery from the alternator and no control wires for the fields of the alternator. Battery voltage is monitored through the charging lead. Moparman is correct in his statement about a smarter charging system controlling voltage regulation using the temperature sensor on one of the two batteries. In my case increasing battery life is a mute point as I was very close to launching a 50 caliber round through this Dodge. It was purchased as a project truck and in all my infinite wisdom "Dumb-A" I thought I was just going to build a new rear end for it and put it back on the road. Hahahaha....

IMG_20200922_143526.jpg

I now have 400 miles on this truck and am getting use to driving it. It has lot of power and is getting around 14 mpg, seems like it should be better? Again I have no history with this truck!!! I don't know what had been done to it. Other than neglect. No blow by and after changing the oil it now has 400 miles on it and the oil still looks clean. 

This is what I've done so far. The 6 speed manual transmission was rebuilt around 4600 miles prior to me purchasing the truck. Time will tell how much more I'm to do on this truck. 

16096088059306474493218858213819.jpg

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On 1/2/2021 at 4:32 AM, Mopar1973Man said:

I just decided to go with a one wire alternator ( self regulated) hope this answers your question.

 

On 1/2/2021 at 4:32 AM, Mopar1973Man said:

Just remember that your battery life span will be greatly shortened.

 

Not necessarily.  I think that the predominant surrounding environment, the duty cycle of the truck, and the quality of the battery play a large role as well. 

 

I bought a 1991 Ford F150 4x4 truck new and immediately installed a Cummins 4BTA 3.9 liter engine.  The OEM external voltage regulator was located in the right side fender well.  After five years of driving in the vicinity of Leadville, Colorado (10,200  ft elevation) and four years of driving in Redding, California (100° everyday throughout the summer), the single battery was still passing load tests after 9 years and over 200,000 miles of operation.

 

I like the idea of a temperature sensor under the battery to increase battery life, but if the PCM on my truck fails to charge the batteries properly, I will more than likely switch to an external voltage regulator.

.

On my current truck the OEM batteries lasted for 10 years (178,000 miles).  The second set lasted 6 years (115,000 miles).  The current set (Group 24's) have been in use for 3 1/2 years (about 45,000 miles).  I think my OEM batteries were the best quality.

 

- John

 

 

 

 

 

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