Is it safe to assume that my truck is set up for snow plow because it has dual alternators? I think one of my alternators is going bad. On my scangauge i run my truck and the batteries stay pretty constant at around 14 volts. When i run my plow up and down like we do, my voltage drops to 12.0- 12.5 volts and it usually takes a fair amount of driving to get the batteries back up to 14. It seems to me that i am losing an alternator. What do you guys think. I have an 04 F350 6.0L


also what amperage do the stock alternators come at? I figure 110 or 120

 

The normal running amps warmed up is 50-65 amps, add in snow plow set-up and that will tax the charging system even more.

The upper is a large case 6G alternator and 140 amps, the 4G lower alternator is 120 amps

Josh

 

I would test both alternators. I have had alternators go out on the dual setup and never show the charging light! I noticed my voltage a bit lower than normal, no light but when testing found my upper alternator was not working. Replaced both even thou the lower showed good. Now voltage is 14.2-14.5 even at idle depending on temperature.

 

Brandon I plow with my truck as well. My alt works fine but when the plow is in use it drops the voltage down to roughly 12 volts give or take 2 points. After the voltage drops it takes roughly 15-30 seconds for the voltage to recover to the 13.8 range. And its faster when I rev the motor, takes longer when idleing. It is normal for this to happen. Its like the difference between static and operating water pressure. This is hard on batterys so keep your receipts. And watch for failures or signs of it. My last set of walmart batterys lasted about 18 months. But that was two plow seasons. They have a 3 year full replacement warrenty. And they will replsce both if one has failed. As long as you tell them its for a diesel truck.

 

Definately sounds like you have one or both alternators going out. They get really hot, so individually load testing out of huge truck is paramout. I would replace the upper to a larger alt like my Leece Neville in signature at 230 amps, a new lower 120 will be the backup when the larger one is too hot to produce. I would also advise upgrading all you positive and negative cables to 0/0 or double zero with big ends crimped and soldered and use dielectric grease on all bolts. Those plows pull a lot of juice, bigger cables are needed for the above alternator, it's rated at 230 amps. You also may want to consider switching batteries around once in a while as the passenger side takes all the power form the bigger alternator at least.

 

Hey Josh so can I replace the lower 120 for a higher amperage? I want to maybe go higher on the amperage if I test them and they are bad.

 

Yes, there are couple different vendors that hot rod the 4G alternator. I know Lilpooh has both of his alternators upgraded.

Josh

 

Thats what ill be goin with probably because of all the things i run in the truck. Just bought two new interstate batteries, probably the best desicion in batteries ive ever made. Thanks gents

 

The PCM is instructing one or the other alternator to charge, so effectively, you have to upgrade both to get what you are after. I agree upgrade the bottom one, but you also need to do the top, if they load test as not being up to par charge wise.
Mike

 

That makes sense. Ill be upgrading both.

 

Is there a dual alternator how to guide anyone can guide me to? I wanna do em myself, it just seems like the lower one could me a b*tch to get to.