83 SD electrics work but battery goes dead when running?

[Fredmburgess]

I installed a PlantDrive conversion in an 83 SD last week (added two solenoid driven valves and a 30 amp fuel heater to the electrical system).

Everything worked fine, car ran great on diesel or WVO. Owner drove it about 100 miles to home with lights, heat, radio, wipers and WVO system running. No dimming of headlights or other signs of failing electrical output. Parked car, two hours later would not crank, no restart, lights dimmed when attempting to engage starter. Started with a jump, drove another hour with lights, etc., on. Shut down without trying to restart. No start this morning (again no crank, apparently battery dead).

Battery has been ok, car started fine after sitting nearly a month (prior to delivery to me). Ebay special so age of battery and car history unknown. Car is new to current owner and this was essentially it's maiden voyage.

My question is (sorry for long winded stage setting)...

**Is it possible for the alternator to support electrical demands of lights, heat, radio, etc, for a couple of hours of highway speed driving and yet NOT also charge the battery or somehow lead to battery drain? **

This of course assumes that the battery is ok, and we know what assumptions lead to. I had no problems with the car so never tested alternator output while it was here. It sat for 10 days or so and started every day without issue.

I've suggested that the owner take the car to Autozone, or similar and have the battery load tested and alternator output measured. Many other 123's and 124's have tolerated the additional electric demand of this conversion without issue.

Bad voltage regulator? Other suggestions?

Thanks all!

Fred

[Brian Carlton]

Originally Posted by Fredmburgess

**Is it possible for the alternator to support electrical demands of lights, heat, radio, etc, for a couple of hours of highway speed driving and yet NOT also charge the battery or somehow lead to battery drain? **

It is not possible.

Either the battery is toast and it won't keep a decent charge or the voltage regulator is toast and it won't provide sufficient current to charge the battery.

Only a voltmeter knows for sure.

[kolwrath]

I would put my money on dead battery. Take it to a shop and get it tested.

[LUVMBDiesels]

Remember that the stock alternator on the SDL is only 70A. If he is pulling 30A for the heaters he could be drawing more that the alt can supply and getting the rest from the battery...

I would shut down the plant stuff and drive it on diesel without the heaters to see if the alt can keep the battery charged. You probably need to go to a bigger alternator. There are posts about swapping the stock one for a 140Amp unit.

[Fredmburgess]

Sorry for delayed response, all. I couldn't diagnose because the car was already gone back home. Owner had alternator/battery checked. Alternator ok, battery was in fact toast. I suspect that with lights, heater blower, wipers and the electric fuel heater there were more electrical consumers than the alternator could supply so balance came from the battery. New battery has resolved for now, but I agree that a higher output alternator is probably in order. Thanks for the responses. Other than that the Plant Drive system with a simple
controller worked well and the car ran great on WVO. Fred