over charge on the alternator

[BDWilkinson]

Hi every one,

this is my first thread here and i am hoping to get some better advice than my local dodge dealer has been giving me. i have a 2006 dodge 2500 with the cummins CR motor and have been having over charge prioblems for the last 8 months i went through 4 alternators and 1 PCM (which was supposed to fix thye problem but didnt) My truck throughs a P2609 code engine grid heater voltage low and then the alternator will go into over charge this is the first time that it has done this in the 4 weeks since the new PCM was installed. But before it was installed it did it every day. could there be a bad grid heater causing this or maybe a bad solenoid, or is it the battery cables like my dodge dealer has suggested,( the cables have all been replaced ounce already and are very clean) i am at my wits end with the charging system on htis truck any help or advice would be greatly appreciated.



Thank you in advance

 

[jelag]

I think you need to do some research... I'd grab a digital volt meter and connect it to a power plug and install it in the dash and monitor the voltage... this alone will give you a piece to the puzzle... If I was really interested I'd run another set of leads to the grid heater and look at the voltage in the morning when its running to see if it is really low... .

Also any loose connection in the grid heater circuit or a bad or missing ground could give you a low voltage reading at the PCM. And the grid heater circuit might be functioning normally...

The alternator on our trucks are temperature compensated so that the batteries can't be overcharged. So this temperature circuit could also be part of the problem...

They are in fact throwing parts at the problem, as the alternator if fully controlled from an outside source and they just don't start to overcharge a battery... . Just like a thermostat that sits on the wall controls your heater, the voltage regulator circuit in the PCM controls the alternator... if you house is too hot you don't put in a new furnace, you fix the thermostat...

Also remember that they delay the start of the alternator during cold start and warm up, to get the engine past a very bad idle... if you were to watch the fake volt meter on the dash you'd see that it really doesn't go up scale for 2-5 minutes into a cold start... A warm engine restart is different... .

One last thought, if you were really overcharging the batteries a lot... you'd see them gas off... which is moisture around the caps to the cells... the excessive gas given off during excessive charging will condense in the cap and drip and vent to the top of the battery as a wet spot...

Hope this helps. .

 

[BDWilkinson]

Hi Jim,

First thanks for the reply, second the tops of the batteries do show sigh of venting just aas all the previous times and the last time when this happened the alternator was putting out 35. 7 volts according to my volt meter and that is when they said the PCM was bad but now i am back to where i started. I will check all connections again on the grid heater and check the battery heat sensor as well and again thankyou for some pointers



Ben

 

[SWiller]

Check a ground right behind the ECM on the block it's like a 12-14 ga wire coming from the wiring harness. Remove it and clean the connection.



This is what i had to do to mine it was very rusty, but my problem was that my alternator was not charging, and i also went through battery's, alt, ECM. #@$%!



Hope this helps.

 

[B.G. Smith]

Hi Jim,

First thanks for the reply, second the tops of the batteries do show sigh of venting just aas all the previous times and the last time when this happened the alternator was putting out 35. 7 volts according to my volt meter and that is when they said the PCM was bad but now i am back to where i started. I will check all connections again on the grid heater and check the battery heat sensor as well and again thankyou for some pointers



Ben

Where are you checking the voltage? I know the alternator is capable of making high voltage but I didn't think it could get that high connected to a 12 volt battery or two in parallel without blowing up the battery. Gasing the battery would be an understatement. bg

 

[abrankod]

The ECM in the 06 modulates the field of the generator (therefore the voltage of the main output) by grounding the field wire at a frequency up to 100Hz. If your system is overcharging this severely, I'd assume that the field wire between the gen and the ECM has chafed to ground somewhere along its length or in the connector cavity itself. Since the issue is unresolved through generator and ECM changes, we'll temporarily assume that the ECM is not at fault, however if after probing the wiring between the gen and ECM the issue is still unresolved, try leaving the alt field disconnected and probing the gen control line again and see what the ECM is actually doing. The generator control wire is an 18ga Brown/Graystripe. Located in pin 2 of the connector on the gen. The mate is on the ECM pin 7 on the C1 connector.





Frankly though, after 4 alts, and one PCM, I'd be looking to start lemon law proceedings on this vehicle... If not for all the lost time, then to teach the dealer a lesson about not hiring incompetent mechanics.





Good luck,



-Dan

 

[sag2]

Where were the meter leads when you saw 35 volts? If the battery sense circuit has high resistance the ECM will try and full field the generator until the sense voltage is what it wants to see. Also if the generator output wire has high resistance to the battery(s) it will also show very high voltage if your meter was on the output wire. The only way to really prove it out is to read what the ECM sees on the scan tool. You need to see what target voltage is compared to actual.

 

[betterthanstock]

Make sure you (or dealer) clean all connections (the smaller wires) that end up at the battery terminals, on both sides, and if you say the wires that connect the two batteries are new, make sure they're clean. If any acid has spilled, the contacts corrode.

On an older car (some relative's), after going thru 3 alternator rebuilds, we double grounded the alternator, and double wired the positive to the battery. End of problems. But on this, the ECM is where the charging regulator is, so good connections to the ECM are essential. If you were out of warranty, rather than replace ECM, I would put in an older style alternator with built in regulator, wired directly to one or both batteries, and be done with it.