Quote:
Originally Posted by Mikey616
I have a 1987 300D (W124 with the OM603) and recently I've been having alternator/voltage regulator issues. Last week I replaced the voltage regulator (which looked original) with an AutoZone regulator, and it worked for about 200 miles before my lights dimmed and I had low voltage again. I pulled the negative wire off the battery and tested the voltage from the alternator; 6ish volts. Not good.
This afternoon I took the regulator back to AutoZone and exchanged it for a new one. I put it on, started the car, and once again I'm getting 5-6 volts out of it.
So did I screw something up?
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Removing the battery ground very likely screwed something; it causes a large voltage spike. Even if nothing was damaged, the voltage reading of an open circuit will be inaccurate; the reading must be taken with a complete circuit, under load.
Quote:
Originally Posted by Diesel911
You did not mention the Battery being recharged.
If your battery (or the connections are poor) is not good the alternator is not going to work properly.
Also what was the reason for removing the ground cable?
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A fully charged battery is necessary to obtain a correct reading of the alternator charging voltage.
Quote:
Originally Posted by Mikey616
Thanks for the comments.
Is there anything besides the alternator or regulator that could cause me to get only 5 to 6 volts? The reason I unhooked the battery ground was to check alternator output with my volt meter.
Diesel911, are you saying if I recharged my battery the new regulator might be fine? It's low now and I did have to jump start the car.
Also the battery is new; replaced in January 2020. OReilly tested it and said it was good. And the alternator seems to be in great shape when I look inside it with a light while the regulator is removed.
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