Yesterday, I lost my charging system. I had to have friends come and jump me several times so I could make it home. I cant find any easy info on testing the alternator directly from the posts. I bought a new alternator, installed it, and I still have no charging system. Im trying to figure out where the wires going from the alternator go. The big red one (I think it goes to the starter) is hot all the time. The other two arent, and I cant find any info on what the wires are, and where they go to, so I can look for a fuse link, or something. I guess the voltage regulator is in the ECM, so hopefully that isnt the cause. Anyone have any ideas?


Edit: The other two posts are measuring about 11.5 volts(same as battery) when engine is running. Thats from the charger.

 

With the engine running, you should be getting 13.5-14 volts DC at the battery terminals with a properly functioning alternator.

 

Yeah. I'm aware of that, which is why im here.

 

Had your battery tested lately?

just an interesting video on battery tests to check out...

 

Truth be told, todays batteries are more difficult to properly test and I strongly recommend one of the new electronic battery testers. Harbor Freight or Northern Tool should have one, personally I like this cen-tech 66892. Else try amazon or ebay. When you test yours, look for 650 - 850 CCA for a Magnum V8. Oh by the way, if you are still using Shumacher battery chargers its time to buy a new one. We have 4 here - all less than 4 years old - and they all overcharge so sadly I can no longer recommend them. They work (sorta) and are fine for emergencies but should only be used for that purpose. If you wanna know how to keep charge your battery charged while your RV sits over the winter, start a new thread and I'll give my recommendations. Hint: Battery Tender isn't on our list


Back to the OP's question, any ordinary voltmeter will tell you wether or not the alternator is charging your battery. Be sure you check and clean your battery terminals before you proceed as dirty terminals will cause voltage drop.

Measure the voltage across battery terminals. It should read around 12.6 - 12.7v ( normal flooded lead acid battery) or 12.8 - 13.2v (agm) if your battery is good and has full charge. Start the van. After a minute or two the dash voltage gauge should jump up and read 14 to 15v or better. Measure the voltage across the battery terminals, it should now read 13.5 - 14.5v. If your reading does not rise to this voltage the fusible link in the alternator wire is blown(replaceable) or the voltage regulator inside your PCM is bad, and PCM must be replaced.

Usually if the alternator is charging (read voltage off the large terminal at rear, 16- 18.5v is typical) then the fusible link in the wiring has blown. Locate and replace the fusible link inside the wiring harness. If the fusible is good, the PCM is most likely bad.

 

I ended up taking it to a shop. The ECM is bad I did manage to find a replacement online though, so I'll have one soon. Thanks.

 

Oh man, I'm sorry. You can add an external voltage regulator but I think your CEL light will stay on so I think you are doing it right. Best.