I found a rebuilt ecm....installed it still charging 15v at the battery..? all the fuseable links are staying cool, take it for a ride ...at this point F it....good couple miles ...radio,heat,...run it up speed wise ..? come home check it every things normal ...shut it off cranks right back up...ok ill use it to take the ecm core back.....yeah right 2 miles stop for a flagman...thats where it stayed ...135 tow job later here I am again....truck cranks ..has lights ..radio...windows jus dont run..I suspect the links again...wrong they are good ...yank the ecm out put mine back in...cranks right off ?...wtf...I have now 14.8 at the batt...14.9 with all the accy's on.......before I burn this relic what now ...HELP(again)

 

Could be a shorted/broken wire that provides battery voltage signal to the ECM. It could be a shorted wire in the alternator field driver circuit.

 

Thanks Seal...I'm sure with my luck I'll be back...im gonna start by swapping batterys with my 55...Haynes says a bad cell could cause a overcharge issue...if thats a no go I'll start with the alt harness and work backwards....Im really not ready to give up yet....

 

HAH...back again dodge lovers...checked the wiring,redid grounds,batt terminals ,found a short in the power door locks ...still over charging....purchased a mopar ecm...yes theystill can get some parts for this vintage ...ok cool install runs ,,,,,F'n still overcharges ....could the 120amp alt be too much? the other options are 75 or 90 this truck has every power option but power seats ?.....my next option is photos to the classifieds ...willing to trade for any 4x4 GM....lol

 

The size of the alternator isn't the problem...but it is possible you have a bad alternator but first do as Seal mentioned you need to verify the wires going to the Field terminals.

The J2-DB (dark blue) wire goes to the ignition switch...so you will need to get up under the dash and disconnect the ign switch and check the connections there; loose, corroded, etc.

The R3-DG (dark green) wire goes back to the computer.

Also do you have any codes in the computer? Specifically 41, 46, or 47?

 

It isn't possible to have too high of an amp alternator. Pull the field wires and tape them off to insulate them and see if it is still over charging. It shouldn't charge at all with the field wires disconnected. If it charges the alt is bad. Be sure the alternator has a good ground as a bad ground will cause random problems. Are the battery terminals and the engine/frame grounds clean?

 

there are no codes with the exception of 12,yes the batt terminals and frame grounds are good , I will check the alt first as its easiest ...then im sure its under the dash again to check the wires at the ign switch....I'll be back for more support or a success story ...thanks guys

 

ok no success,anyone want a 92 w-150 with a bullet hole in it..lol, so heres todays results ...seal I redid the alt test and rechecked grounds ...all good ,did not drop the steering column yet ...but rewired alt fields and ground an hot leads...the field wires are as follows ,green goes to ecm,blue goes to a terminal that runs to pass side injectors and what seems to be a purge valve ?...heres the numbers ff the alt main feed 15.3v off the blue wire 14.6V,green bounces between8.2 to 8.8.......batt side :15.04v....w/heat an lights 15.09 put it in gear 13.34v ? turn off heat an lights15.04v....this is at idle....drop the column or ?

 

Take the alternator off and take it and have it tested.

The blue wire does supply power to a number of items under the hood as well. It starts at the ignition switch and goes to a splice at the right rear of the engine.

 

In looking through the FSM; I'm very surprised you don't have codes 41 and 46. Both should be setting if your over charging.

1. Have your alt tested
2. Chances are the wiring at the ign switch is ok since it is charging

It is possible you have a bad computer if the alt tests good. Then you could either swap computers or install an external regulator.