Having problems with a 97 5-speed. Have replaced alternator, checked all external fuses and still cannot get it to charge. Any ideas other than replacing the ECM at a huge cost!!

 

Have you taken a multi-meter across the battery terminals to verify that you have 14vdc. If you do then time to start looking for something that has shorted.

 

It could be anything from the Crankshaft Position sensor to a blown fuse for the alt. You didn't just get done changing the oil did you? If you accidently hit the terminal on the back of the alt. you will blow a fuse. Try reading this thread and see if it helps: https://www.dieseltruckresource.com/...tage+regulator
There is even instructions there how to by pass the ECM and install an external voltage regulator.
Tom