2nd Gen Non-Engine/Transmission Charging Help!

[norcalram]

My allternator died last week on my way home from work leaving virtualy blind. needing to be back up and running by the next day, I bought a new unit from napa, some generic brand but 136 amp. Put it in, put the charger on the optima red tops (about 2 years old) and took off to work the next day. Problem is, its only putting out ~11. 3 volts. I only work about 3 miles from home, so i have to put the charger on every couple of days. i'm understanding that the diodes are part of the alternator, so i'm assuming with a new alt, it shouldn't be bad diodes. Would the pcm or rectifier cause the origainal alt to go bad and a new one to not allow a full charge? Im planning on rebuiling my nippon and possibly putting it back on because its probably better than the new one, but i'm thinking that won't solve the low charge either?????

 

[Road Dog]

The voltage regulator is built into the PCM. The alternator can be tested off the truck and if it's fine then you have other issues -- like a faulty PCM.

 

[DMcLeod]

Ditto: (From my 01 24V Shop Manual) The electronic voltage regulator is not a separate component, it is a circuit located within the PCM. If replacement is necessary, the PCM must be replaced.



Other things to check:

test the batteries (even new batteries can go bad)

inspect the cable connections

inspect the serpentine belt/tension

 

[JDKammin]

Does your tach work? A bad crank sensor will prevent alternator from working, but tach will not work if sensor is bad.

 

[norcalram]

Yes, the tach works. is there any tests to do on the vehicle to verify that it is a problem with the pcm? The shop verified that the old alternator was bad. (so they said) would it be likely that it and the pcm would fail at the same time? I read there is a way to bypass the pcm with an external voltage regulator but i can't find the post. Anyone know how that is done, if nothing else just to verify it's the pcm.

 

[WilsonF]

You said you got a new one, is it really a new one or rebuilt? If rebuilt it could still be a bad alt. The record on rebuilt alt. and starters is not very good. Go to this link, shows how to wire in an external regulator. I did this temporally to test the PCM. If you find that it fixes the problem leave it on.
Truck no charge-y! - Page 2 - Dodge Diesel - Diesel Truck Resource Forums

Floyd

 

[norcalram]

I heard bad things about the rebuilt ones, so i made sure it was new. Actually cheaper because of no core charge plus I want to rebuild the old one for $30 even just to have as a spare. Is it possible that the old alternator caused damage to the batteries and the new alt works but the batteries just wont hold enough of charge?

 

[DieselDoghouse]

Not likely the old alternator did much to the batteries unless it overcharged and cooked them. Testing the PCM requires special equipment (drb tool) unles you bypass and regulate charging outboard as suggested. Any chance you just happened to have a battery with a bad buss bar? Have they been load tested??

 

[Missouri Mule]

There is a Battery Tempature Sensor located under driver's side battery tray check to see if is bad. Wrong or no battery temp signal the EVR (electronic voltage regulator in PCM) will not be able to control battery charging rate.



The EVR also needs a signal (line voltage) from Automatic Shutdown relay(ASD relay) also so check out this relay( the engine speed sensor activates it).

Another words the EVR needs input from both the BTS and ASD relay to control output of Alternator.

 

[norcalram]

Still haven't had time to thouroghly test anything. Went out today, haven't driven the truck in three days and did't have it on the charger. decided to check battery voltage before anything and they were at 12. 6 each. truck started right up! ran it for about five minutes and rechecked voltage while running and was at 11. 4??? temps have been at freezing at night and in the 50's during the day. I will check this out tommorrow. Thanks for the suggestions.

 

[norcalram]

Alright, in order to save anyone who might read this post who is experiencing any similar problem, I am going to publicly sacrifice my dignity. Before going through all the trouble of testing this and that and trying to diognose for hours on end, PLEASE CHECK THE FUSE IN THE PDC! In my defense, it was not ever suggested to me, even the factory service manual doesn't suggest this step! I still am not sure that the original alternator was bad. Had it still been good, the same conditions would still exist. the batteries lost charge(radio, wipers, headlights were on) the volt meter went low. I replaced with new alternator, charged batteries on charger. it worked fin for a couple of days, dash guage was showing battery voltage, not charge voltage, then i would put back on charger overnight thinking I just wasn't getting a "full" charge. Tip #2 - when checking a fuse (which I had done) don't just LOOK at it. pull it out and check the Ohms. It looked good visually, but was blown.



Speaking of which, where can you find a 140A fuse. I have been to Napa, autozone, Pepboys, and Kragen(o'rileys) they have 120A fuses and the base is too long for the PDC. the 100A and smaller are the right size base but obviosly will not work. I got the 120A for now and cut it down and redrilled some holes to fit until I can get the right one.



Thanks guys for the help.

 

[RBonacci]

I just bought one at OReilley Schucks, $3. 99, Here in Wash.