I have a 01 excursion limted 7.3l with 186k miles.

I have been searching alot and i know the alternator is undersized and crappy...but...

(All measurements are through torque pro and my obd2 adapter)

-i recently redid the terminal ends on the battery cables. Didnt go though everything, but fixed my issue of very low voltages with key off. Passenger battery + terminal wasnt doing its job. I did all the grounds and positives at the battery, with crimpped lugs and hydraulic press. Improved voltages greatly.

-key on engine off...with glow plugs on is now at about 11.1ish, when the glow plugs turn off its at about 11.8ish

Key on engine running at idle, its about 12v ish. It fluctuates a bit. Honestly not much hogher than above.

While driving while warming up, it hovers around 12.5v

once warm its around 13ish volts booting down a highway.

-sitting in the drive way after a short drive today(after the pics), with the batteries connected, but key off is 12.2v

Whats throwing me off is im not seeing 14 volt anymore. I used to, but not now. Im also noticing that full batteries should show around 12.5 volts with the cables connected im thinking if they were full.

Dash idiot gauge is nice and high. No battery light at all. Truck is starting decently now too after the battery cable work.



Engine warming up while driving.

Shot of the idiot gauge.

My question...is the alternator dying a slow death? I have always known alternators to generally just fail outright. Should I get myself a 6 leaker alternator?

Am i just being paranoid because the alternator doesnt need to work as hard because of the improved connections?

This is mostly coming up as a recently changed jobs and my commute is now very short (3mi or so). I do a loser lap here and there to make sure it runs if there are a few short trips involved, but this is my reality, and i think my alternator is not up too the task.

 

Measure voltage at big lug on alternator to see what its putting out. May help rule out corroded or poor terminals.

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I used to have a 7 minute commute, it was murder on the batteries. Especially in winter when it is dark to and from my 12hr shifts. After a month I could tell they took longer to crank it over and would get on the highway and run the truck bypass loop so the RPMs would be higher for 30 minutes and charge it up and get everything up to operating temp as well. Then I started hooking up a small 5amp smart charger every time I'd plug the block in below freezing and that helped a lot. Now I have a 10amp maintainer permanently mounted on the PS fender for the past 4 years and randomly plug it in throughout the year. Plus we moved, so the 18 minute commute helps a lot

 

I'd probably disconnect the batteries and charge each one separately. Then see where they settle out for an at rest voltage. You could have a bad battery pulling down the other and over working the alternator. You want to see at least 12.4 resting voltage from each battery, and they ideally should match exactly.

 

Alternator voltage will drop as the brushes and slip ring (commutator-like part) wear out.

 

The 10amp charger is a strong option. Its tough because i am using the block heat, but its on a timer...so that means a second cord....for now.

I did check the voltages and they were the same. Its gotta be the alternator.

I didnt ohm the alt cable so ill do that(especially since i can isolate it now), but i think i am just going to upgrade the alternator.

 

I agree on replacing (with or without upgrading) the alternator. If the batteries are going bad, it should still show higher charging voltage than that unless things are really bad.

How old are these batteries?

 

12.5 is not even close to getting the batteries charged, not matter how good they might be.

the alternator must be able to push them to 14.4 or higher to fully equalize the cells.

I bought a big 320A alternator, because I have big winch on the front, and tow a bit, it is over-kill but it keeps things rock solid all the time.

it is a Mechman 320A, cost around $500ish

this chart shows you the voltages needed to charge batteries.

 

I got my new to me truck about 6mo ago and I was seeing voltages very similar to yours, or even lower as it fluctuated. I realized while doing some other wiring (mirror upgrade) that my pcm wasnt mounted in the plastic cage. Ordered the cage with the ground strap and instantly had higher voltages - not 14v but went up to mid - high 13's idle or driving, far more stable. Coincidence... I think the ground gave better ref signal for the pcm.

 

Batteries are 850cca kirklands, about 2 years old. The batteries themselves seem fine. They were both 12.6 when i took them out for the cables.

Issue with the really big alternators is that they are crazy expensive to get to canada...and the local ones that big are 4 digits.

I dont plan on a winch or any other large load, so im think a 140 amp from a 6 liter will be better than what i got....and not 4 digits to buy. I think there was a way to get a 6.4l one on there too.

It did output 14.2 once upon a time. It was getting lower in the last month so i did the battery cables as the one was clearly bad while probing around.

I was hoping it was just the bad connection

 

your Alt should put out 14.4v. Just get a bosch or oem alt. the stock alt is just fine. I believe they are 130ish A.
Having good AGM batteries is more important. If I can run a 4000+w stereo system on a Bosch alt and a set of the best AGM's; you will be perfectly fine.

as mentioned, you should check voltage at the ALT though

 

I dod check the alt voltage and it was the same as the system. Ill check again afterwork today.

Agm are too much $$$ in Canada. Cost of living here is something. I can get 3 reman alts locally for he price of 1 agm. Canada is silly for some items that way.

I will get the on board charger and rig up a on board timer. Good boxing day shopping. I want to get a diesel fired coolant heater too, though that might come later. Im going to be doing a coil swap soonish, so i wanna make sure i stay focused on that.

 

I got a new Bosch 6.0 130 amp alternator off rock auto for like $170 something. Not sure what that would be up in Canada but worth checking.

 

Ok update.

Alternator voltage at ther terminal is basicly the same as system voltag, a hundredth or so off. Tough to measure accurately as the voltage slowly rised. Around 12.5 or so driving. Idle is 11.8 now. There is a slow and steady decrease with idle voltage. I had to run into town with it after work so it got a decent drive today, about 20mi or so no reason i should be seeing a low voltage...

I replaced the alternator lug, lowered resistance a bit with the batteries fully disconnected.

Got the trickle xharge on it now to bring it back up.

Seems like all roads piont to the alt.



Going down the highway



Start up after the alternator lug change. Alternator voltage basic the same. The truck is in high idle


EDIT: Alternator was quite a bit hotter than the bracket after the 20mi drive. Almost too hot to touch.

 

Ordered a bosch. Should be here on the weekend.