My 05 F350 turned over slow today and barley started. 12.4V with key off and 12.7 at idle with a good meter and 12.9 on the Bully Dog. This is after I found a lose wire on the top Alt. Cleaned and tightened main alt wire. If one Alt is bad is there a way to tell wich one? I will take the top one off tomorrow and get it checked. I watched the meter for a couple minutes and stayed very close to 12.7 after the glow plugs cycled. 12.71V + or - .05V

 

You need a good DC current meter to tell.
A clamp on would be the easy way to test.
FYI : Not all clamp-on's are DC some are AC only.

Sean

 

You SHOULD see 13.5+ after a start (many reports 14+) once the Glow plugs turn off. Could be you have bad batteries as well that won't hold/take a charge and that in turn can kill the alternator(s) - you should have everything tested individually (ie: REMOVED) otherwise you are just hoping. And you should always replace BOTH batteries at the same time - EVEN if only one is bad, since when the 'other' battery goes bad 'next time' it can weaken the other battery an you repeat this again.

 

And as an FYI: low voltage can lead to a FICM problem and then to injector issues.. New batteries/alternator(s) are cheaper and easier too!

 

Hopefully Lilpooh will be along to explain the operation of the dual alternators, but it seems strange that:

The PCM switches between the main alt, the aux alt or runs both alternators as needed.

So with hardly any running voltage something is whack as it seems unlikely for BOTH alternators to crap out at the same time.

I would almost look at a wiring or harness issue.

Josh

 

you can also do an ac ripple test with your dmm set to ac volts. I don't know what the spec is but if it is putting out ac voltage more than say .5 volts ac, the rectifier in the alternator is not converting ac voltage to dc voltage.

 

I pulled the batteries and both are maxing out my battery charger 1 at a time. I put it on 1 for a couple hours and its still at 15 amps. Last time I put new batteries in was 08. And yes both at once. I just got the truck back 2 weeks ago. I had Badger Diesel do the HPOP + all fittings and STC, also EGR delete + the Bully Dog and new EX. I will take both batteries in and get them load tested tomorrow. My meter will only do AC amps. I will borrow 1 from work that does DC Amps. If the batteries are good I will get both Alt checked. And yes I know it needs to be fixed before the FICM goes again. EDSFICM just redid mine a couple months ago. Thanks for any info.

 

Both batteries load tested good.
Both Alts. putting out close to 100 Amps when first started. First one then I can hear a click and it drops to zero then clamp on the other. After the glow plugs cycle it slowly goes down to 60 Amps + or - 5 Amps. On one Alt wire it shows -Amps and the other is ok with the meter on the same way.
Looking for wire or pin problems. Any ideas????
Should I pull the Alts and have them tested?

 

Pulled the top Alt and had it tested. Its bad. Going to pull the bottom one and have it tested tomorrow at lunch.
I think 1 Alt went causing my FICM to go bad and now the other one went.
There goes my beer $$$$$ for a week!

 

Damn... that's a lot of beer!

Josh

 

Bullit390. Beer is good.
I will get the lower Alt checked at lunch. Might just buy both even if the lower one is good.

 

Both Alts bad. 2 new ones from Ford $497 of poor tim's beer money later. 14.01V -13.85V Good to go now. Please send beer!