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Randall C
Randall C, ASE Certified Technician
Category: Car
Satisfied Customers: 12803
Experience:  32 years Foreign / Domestic Cars All aspects of Diag and Repair
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I have a 97 Isuzu trooper and have installed 3 reman alternators

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I have a 97 Isuzu trooper and have installed 3 reman alternators from advance auto in recent weeks and it is still not charging correctly. It will show 14+ volts while idling but will drop to the static battery voltage of about 12.6 volts when the engine is accelerated rapidly. If I accelerate slowly the voltage usually will not drop. I have checked my ground and other connections the best I could and could not find any issues. Is this an issue with reman alternators or is there something else going on?
Hello, I am Randall. If all connections are good, you have tried several alternators to no avail, then yes, you are missing something unfortunately. The charging system on this vehicle is ECM ( computer controlled)The ECm is is what senses the load and applies the "gain" to the internal regulator. By symptoms, troes etc? I have to lean to a charge control circuit within the ECM has failed. I can not be 100% without viewing live data on a scanner but everything is now pointing to a bad ECM. Actaully in most ECM controlled vehicles, the ECM is at fault before the alternator. I have included the wiring diagram showing the ECM int eh system
Customer: replied 4 years ago.
Thanks, is this something I can replace myself with pretty good mechanical experience and do you know where the ECM is located?
You can do it, its under lower center of the dash as shown. Have to remove the consol around the shifter
Now,, if you buy at a parts store, most can have it programmed for you as well as at the dealer parts dept. Any new ECM must be reprogrammed
Disconnect the red, white, and blue electrical connectors at the PCM.
Remove the two screws in the front of the PCM.
Remove the one screw at the left rear of the PCM.
Pull the PCM straight out from the dashboard.
Insert the PCM into the dashboard.
Line up the holes in front for the mounting screws.
Install the PCM with two screws in the front and one screw at the left rear.
Plug the red, white, and blue connectors into the appropriate sockets.
Install the PCM side cover.
Install the PCM front cover.
Install the console.
Remove the wheel blocks.
Connect the negative battery cable. If the PCM is replaced, the new PCM will need to be reprogrammed.
Customer: replied 4 years ago.
Thanks again. I will give it a try.
best I have without scanner info. Hope it goes ok for you
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