24v wont hold charge??
 

2001 cummins wont hold a charge and i dont think its my alt.. anything else i should check??? batteries are good too....

If you pull the battery cable and use either a volt meeter or test light between the battery post and the cable with everything turned off it will show if you have something draining the battery. Have you checked the voltage with the engine running? It should be between 14 and 15 1/2 volts. If it isn't the alternator is not putting out. I think the ECM has the regulator in it.

dont have no volt meter.... running 12.5 to 13 volts at idle... thanks though...

12 1/2 to 13 is too low to charge the battery properly. It would be worth getting a cheep meter. Sometimes Harbor Freight has digital meters for around $5. It's good to have one in the tool box. It sounds like either the voltage regulator or the alternator is bad.

ok well i'm taking the alternator to get it checked... how do i know if its the voltage regulator??

It is back to needing a voltmeter again. One of the small wires to the alternator will read 12v to ground. The other is a variable ground through the regulator. If you take a wire from this terminal on the alternator to ground you should see your charge voltage go up. If it does the alternator is good and the regulator is bad or you might have a broken wire in the harness.

oh well.. i'll get it...

It could also be bad connections between your batt cables and the battery. That's free and easy to check/fix.:U:

are you SURE the batteries are good? Are you sure all the battery grounds are connected right? Sometimes the grounds LOOK good, but the wires under the sheild are corroded

Also check to be sure you don't have a grid heater relay sticking on draining the battery. The intake horn will real hot if it is staying on. It would drain my battery very rapidly when mine stuck and actually got the factory horn hot enough it discolored it.

took off all battery connections... cleaned them and ran emery cloth on them lightly.. brand new batteries and they tested 11 under a load today.. put on new alt... still does it... when u start it volt guage will hold around 13-14 for minute or two..then it bottoms out.. but truck still runs and fuel pressure and everything stays the same... no effect with lights on or off.. it just graduaaly drains over the period of a day or two.. fml

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oh and thanks all..

Does it drain if the truck sets with the key off or only when the engine is running? If it drains with the key off something is shorted and drawing power. If only when it is running it is either not charging or as one of the other posters suggested the intake heater grid could be stuck on. If it is the heater grid you could disconnect the power from the solenoids until you could find out whether it is the solenoid or the temp sensor. If it isn't charging the only thing left in the system is the regulator. Did you check the voltage between the 2 small wires on the Alternator?

shpuld have specified better... it doesnt drain it pretty sure its just not charging while running.. didnt test the 2 lil wires no... ehat are they??/

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should*
what*

They are the wires to the regulator. One of them is supposed to have 12v all the time. The other controls a partial path to ground to control the alternator output. If you test the voltage between the 2 wires it should be less than 12v but not 0.

so they regulate how much the alt puts out??

The simple answer is yes. They control a current flow in the rotor that makes the magnetic field. The rotating magnetic field makes electricity in the outer stator windings so by controlling the rotor current you control the output. It is called the field current.

Try This

thanks DM but thats way to complicated for me... its times like these when i REALLY REALLY miss my old VE truck.. damn electronics.. looks like she's going to the shop..

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Opinions on doing an external voltage regulator or spending the money to fix it factory???

I had to put an outside regulator on our 92 d350. It is not very hard to do but I had trouble finding the regulator wire plug. I ended up getting the plug from NAPA. I think it might set a trouble code in the ECM though. It would be the least expensive way to go.

can't i just splice into the wires on my factory 2 prong plug on the alt???

Yes but you need the plug that fits the regulator. I just used the chrysler electronic regulator that was used since about 1972.

Alternator has been replaced, and the batteries tested good, correct?
I am also curious as to how, or who tested your batteries. Having the voltage drop below 11 volts isn`t bad. The true test is to load the battery to half it`s CCA rating for 15 seconds, and voltage should not drop below 9.6 Volts.
I am hoping by this point a multimeter has been purchased, it is an essential item to diagnosing situations such as this. I keep one in my truck at all times.
You could try a "full field" test, which manually puts the alternator into 100% charge. On SOME alternators, there is a "D" shaped hole on the backside of the alternator, inserting a small screwdriver, or other object into this hole will force the regulator into 100% charge state. If you decide to this, do not do it for long, and once again a meter is required to monitor OCV.

On a dodge system the regulator is outside of the alternator. Most of the newer ones it is part of the ECM. The full field test is to pull the regulator wire off the back of the alternator and ground that alternator terminal. the other brush lead is 12v. The G.M alternators have an internal regulator with the d shaped hole.

No multimeter... i can figure it out w/o one.. regulator wire= big one that goes from alt to relay then battery??? then what do i do to full field??? mine just has the 2 prong plug in unlike the older ones that had the posts and individual wires..

NO - you need a multimeter to troubleshoot this. You should have at least 14 V at the battery terminals when you start the truck (and Im not talking about the one on the dash).

The big wire is the output. The regulator is one of the two small ones. One of the small ones has 12v when the key is on. The other small one is the regulator wire. this is the one to short to ground to full field it. You really do need a meter to check things properly though. you could get a meter at any auto parts store, radio shack, harbor freight, or even home depot or some other hardware store. Harbor freight probably would be the least expensive.

heres the possibility.... trailer wiring harness got ripped out and was shorting to the bed.... could that have blown my alternater relay/fuse??? shouldnt that relay/fuse go before the voltage regulater???

There are several fuseable link wires in the harness. A short could have burned one of them out. The easy way to test a fusable link wire is to pull on it. If it streches it is burned out.

well thanks everyone for the help i'm just gonna take all day tomo and figure it out..meeting adjourned..

get her done??