Full wave rectifier problem

This is long so please hang in there. I need the braniacs here to help me solve this!

I have a couple of new Kohler engines with some 20-30 amp full-wave rectifiers on them for charging. Under most circumstances it charges just fine. When I put a load on it the DC+ (B+ lead on the Kohler rectifier) jumps from right at 14.08vdc to 14.41vdc +/-. The system is charging and working well. However when I turn on one particular transformer that is 12v and 8amps the engine stops charging. If I measure the DC output when I turn on that transformer I am lucky to get 12vdc. It commonly drops to the high 11vdc range. Not until I turn off that transformer does the rectifier return to the 14+vdc as per normal and then charging resumes.

Here is the crazy part I have this EXACT same setup on 10 other units and I have no such issues. So I wired my new engine to the transformer on my current unit and got the same problem as described above. I wired my new transformer to the current unit and it works as expected and the unit charges. So the problem has to be in the engine and it’s charging system. But aside from the transformer the charging system is behaving normally. So next I wire up another new engine and it is behaving the exact same way. It is blowing my mind. I have been doing this since 2013 I know what I am doing but this one is kicking my butt.

Here are the particulars in case it is needed or is relevant; • Kohler CH730-3226 manufacturer in Sept 2019 (10 other units 2016-2017 same make/model) • Rectifier Kohler 25-403-39-S (20-30 amp rectifier) • Stator Kohler 28-085-02S Stator 25 amp • Transformer Beckett 5218303U 12VDC Ignitor

So in my infinite knowledge of electronics (not so much) I decided I am dealing with a "noise" issue as the transformer is a good deal closer to the engine and rectifier on the new setups, or I am dealing with a full wave vs half wave pulse issue. Don't ask me how I got there, and it is probably totally wrong but I am fresh out of ideas. All I know is I need help. I have tried the local small engine guys and they are stumped. I need some "brain power" to get behind this.

Whoever helps me solve this puzzle will be my hero and I will make sure they are well compensated!!!

by iclmwillard
May 23, 2020

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