Would it be possible to switch the AC in my truck (1988 F-250 XLT Lariet) with an extra alternator. The Ac on my truck is not operational. I am not sure what I have now but I think that it is the stock alternator. I have been thinking about putting high drawing fuel heaters on my truck, like the type for running WVO as well as other devices. Could I simply run the wires from the first in parallel with a second alternator or do I need to install a charging system. Also A though occured, I will have two 850cca batteries comming up and I would like to mount them in the rear of the truck for and alternate use. Is there a way to charge them seperatly with an extra alternator (charge them while driving) rather than have them drain my primary batteries. Thanks

 

If you want to install a second alternator, you will have to modify the AC brackets for it to fit there. I would get a Leece Neville high output alternator like they install on the ambulance package. This alternator has a built in voltage regulator. Set if up to charge the back batteries. If you want to tie the systems together you will need a battery isolator.

 

If you run two alternators at the same time charging the same bank then it will work until the batteries reach the set point voltage of the voltage regulator and then one of the alternators will shut off because it will see the batteries as full. It's best not to have two alternators charging the same bank unless it's a large battery bank.

Now if you put two extra batteries in your bed you can charge them with one alternator and then use the stock alternator to continue charging your start batteries in your engine compartment. Then if you want to combine the battery banks together, you can use a high current solenoid that is switch activated in the cab to act as a combiner. Or you can install a manual combining switch.

Battery isolators are for charging two different battery banks from the same alternator when you don't want the two banks to combine. I'm not a fan of isolators because you loose about .5 to .7 volts across the diodes. I prefer to use a solenoid for combining or you can use a current limiting combiner which allows you to use smaller gauge wire (Blue Seas makes a 60A combiner that allows you to combine with 10ga wire).

As for mounting a second alternator you will need to make a custom bracket and ensure the pulleys are properly aligned. Do you have a serpentine belt or separate belts?

 

One more thing...I'm not a fan of internally regulated alternators only because the voltage sensing happens at the output post of the alternator while an externally regulted alternator can be wired to sense battery voltage directly at the battery. This way you can bypass any voltage drop that happends between the alternator and battery. Internally regulated alternators tend to undercharge unless it's regualtor has been tweaked to take the voltage drop into account.