Alternator size

Even if that alternator & charging system is in perfect is in perfect shape it can't keep up with more accessories than OEM

I can't say what you had for drive ratios on your 340, but the drives from a stock 318 are 7.25 on the crank & 3.00 on the alternator. That is a 2.41:1 overdrive.

So with an 850 rpm idle you would be turning 2048 rpm - just enough to make 28 amps. With some electric fans drawing more than 28 amps by themselves, you are using more power that you are making. Better have a great battery, and drive for lots of miles between stops to recharge the battery.

B.