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Junior Member
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Discussion Starter #1 (Edited)
First, I want to say to all the kind folks here who've helped me out over the years with diagnosing my truck's problems. Your help has saved me hundreds of dollars and made me become a better mechanic. Diesel Garage Rules!

Okay, here's the background & "symptoms":
-I have two new 750 cranking amp batts from Advance in my 2000 F-250 2WD 7.3L crewcab Lariat pickup. One new in January and one new earlier this month. The batt replaced this month was putting out only 165 CCA and Advance was great in honoring the warranty and giving me a no-charge exchange. Prior to this month's batt exchange, my truck was having constant starting problems. I'd have to either charge the batts or drive it around a while to charge 'em up.
-I had no starting problems for three weeks but this Sunday I hopped in my truck to go fishin'. But all I got was a click-click-click. Wouldnt start. Got out the jumpbox and got Ol' Blue going. Nothing stopping me from my fishin', dangit. I got bait at the bait & tackle store and got the click-click again. Jumped it and this time checked the terminals. The right-side pos terminal was loose (my bad) and I cleaned & tightened it down good with a wrench. I reckoned the drive to the boat ramp would bring the batt up to speed.
-I come back from fishin' four hours later with a box full of big ol' Sheepshead and I get the click-click-click again! wth? JumpBoxed it. (best $40 bucks I ever spent at Harbor Freight)
-here's where it gets weird. I'm on the way to the tackle store to weigh-in a big fish for a tournament I'm entered in. I happen to look down at the dash gauges and they are all deadlined! wth? I keep driving and notice the needles keep flickering - jump back to life for a second then deadline again. Oh s**t.
Just as I pull up to the bait store, I hit the turn signal and the engine DIED while I was still moving. Coasted in..... Uh-oh.
-Guy at the store has a 2002 F-250 7.3L and he suggested cam sensor. Just so happens I have one in my glovebox! Ford had replaced my cam sensor a few years back during the recall. I also made sure to buy a new model cam sensor as a spare just in case. I worm under the truck and changed out the cam sensor. John jumps my truck and about 5 minutes later while idling and we're talking, the dang truck dies again. Oh hell, it ain't the cam sensor.
-we're both thinking alternator now so John gets out the jumpers and we give Ol' Blue a good charge for a good 15 minutes. Then I turned everything electrical off (windows up and no A/C in 95 degree heat. Lotsa fun!) and hauled a** for home 15 miles away. Just the occasional braking for stoplights saw the voltmeter gauge creeping lower and lower....uh-oh. Just as I backed into my parking spot at home, she dies again.

Batts: new in January 2014 and early May 2014
Glow Plug Relay: new in March 2013
Alternator & Serp Belt: replaced (reman?) in 9/2011. Warranty expired. Repair shop did the install. Got me good too - $600 for a reman alternator and a serp belt. If I'd know better at the time I could have done it myself for $275 and a sixpack of beer.
Starter Motor: replaced in July 2013
Supertuner Chip: basic chip, towing option, June 2009.

I have no problem with replacing the alternator myself. But I dont want to buy an alternator and waste money if that's not the cause of this latest problem.

HELP!

Mark
Louisiana
 

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Old Fart
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889 Posts
It is probably your alternator. You are charging the batteries up and driving around until the charge is gone and it dies. This is an electronic truck and you must have DC Power to power the ECM and the Fuel injectors. When the power goes out, so does your truck. Good luck!
 

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Discussion Starter #3
DB48 - thanks for the advice. I'll be able to test it tonight now that I finally found my dang voltmeter. I'll charge each batt - test it while engine off, then start engine and test voltage while running. That'll confirm your diagnosis.

I know for sure it's none of the fuses. Dont know how to check the relays but I pulled & checked every darn fuse under the dash and inside the engine compartment. All were okay.

Mark
 

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Member
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You need to monitor the charging voltage while driving. It should be at least 13 volts and should stay pretty steady. It will take a minute or two to get up to voltage. Either take a good quality tester and hook up to the batteries or buy a digital gauge that plugs in your cigarette lighter.
 
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Discussion Starter #5
DB48 & BPogue - yep, alternator.

I have 110v powered batt charger - it has several features including a digital readout of batt percentage and batt voltage. Also allows you to select regular batt, deep cycle or AGM.

Took the voltmeter and with the ignition off I got about a 10.6v reading from each batt.

I didnt feel like unbolting the terminals from each batt and slapped the charger on. The percentage readout was only 10%. I left it charging for an hour - it maxed at 62% - gave it another hour - still 62%. I'm thinking oh crap, the batts are toast too.

So I said heck with it, got the jumpbox and started up Ol' Blue. Let her run for a couple minutes and the voltmeter didnt say 13.6-14.3volts. It only read 11.6v. If the alternator had been working properly it would have been at least 13.6v. Nope.

Alternator, right?

I reckon I'll uninstall the alternator and take it with me to avoid the core charge rigmarole. May as well take both batts with me too and have them check them too. Both are under warranty.

What the hell, this weekend's weather is shot for fishin' anyway. May as well get my paws dirty workin' on the truck.

thanks,
Catch
 

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Stuck in Commiefornia...
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I've done a few alternators on these now. If you take your time and get all your tools together ahead of time it's a 20 minute job. Try to convince the boys at the parts house to swap you out for a matched set of batteries if they test even slightly off. Final thing, check the grounds on your truck. With the gauges acting up, sometimes you'll lose a ground and the powe had to pass through other paths, screws with the gauges and other electrical system items and you can't really tell til the ground fails completely. Just take a few minutes and check, might find something simple that will save you a bunch of fresh headaches in the future.
 
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Member
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well

,take wire off alt,batteries charged,crank engine ,check voltage at alt,should be around 14-14.5 volts,regulator should be fully excited,if under 13 volts its alt,check with meter ok ,you can do this sitting under shade ,ok
 

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Discussion Starter #8
I've done a few alternators on these now. If you take your time and get all your tools together ahead of time it's a 20 minute job. Try to convince the boys at the parts house to swap you out for a matched set of batteries if they test even slightly off.
That was my next question - what tools will I need for this?

I have an el cheapo socket wrench set

I have both an SAE wrench set and a metric set

thanks,
Catch
 

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Discussion Starter #9 (Edited)
Alternator Installed - Next, The Batts

Well, I bought that 110amp alternator (new, not reman - the online reviews at the Advance site seemed to heavily favor buying new. By the way, purchase online but pick up at store saves you 15% + a $25 gift card) from Advance today and my neighbor helped me install it. Tough One brand - limited lifetime warranty.

-I used the 12mm wrench to remove the pos & neg wires from each batt terminal.

-Next, I bought a 12" flex handle breaker bar 3/8" drive with a 1/2" adapter to pull the tension pulley counter-clockwise enough that we got the serp belt off the alternator pulley.

-we removed the wires from the alternator

-unbolted the alternator

-mounted & bolted the new alternator

-installed the wires

-put pressure on the tension pulley and re-installed the serp belt

-re-installed the pos & neg wires to the batts, got the connections clean & tight.

-then I hooked up the battery charger to the batts. Once again, with both batts hooked up, it would only go to about 65% charge.

-I used the jumpbox to get the engine cranked over. Once it was running, I turned off the jumpbox and removed it.

-I put the voltmeter to the batt terminals and kept it there. The voltage creeped up as the alternator warmed up.
1:00 minute = 13.54v at low idle 700rpm, nothing on inside the truck other than the parking lights. (that's a long story in itself). This was the highest reading at low idle.
2:00 minutes + = 13.15v at low idle 700 rpm. It seemed to settle down at that voltage and stay there.

My shop manual says an alternator output should be between 13.6v and 14.3v ? What's up with the my new alt reading like it is?

5:00 minutes + = 12.65v at low idle 700 rpm, everything on - AC to max, radio, turn signal, wipers, headlights

6:00 minutes + = 13.55v at fast idle 1000rpm, everything on

Here's the new alternator after installation and 2 Miller High Lifes. The driver side batt and the passenger side batt, respectively.
 

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Junior Member
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Discussion Starter #10
Batts Making Me Batty

PASSENGER SIDE BATT

Passenger Side Batt charging after 1 hour - pos & neg wires removed from batt

Says it's at 71% but voltage reading says 13.1v. Batt was new January 2014
 

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Junior Member
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Discussion Starter #11
Batts Making Me Batty v2.0

DRIVER SIDE BATT

Driver Side batt, 1 hr charge, says it's at 90% capacity but the voltage says 12.8v. Was new as of 5/01/2014.
 

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Junior Member
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Discussion Starter #12
Once again, I appreciate all the help from all the folks commenting on this thread.

So what's the consensus on what's going on with the new alternator's output?
Is it within norms or should it be higher?

I reckon we all agree the two batts have s**t the bed and need to be replaced. Right?

Catch
 

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Stuck in Commiefornia...
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The bad alternator has damaged the old batteries and because they were replaced at different times that damage will show as different levels of charge. This is why I suggested having them tested and trying to get them replaced as a matched set at the same time.
 

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Old Fart
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889 Posts
What we have is one battery in two places at the same time. Changing out 1/2 of the battery just puts a higher load on the new part (it is doing more than 50%). This is why we suggest, very strongly, changing BOTH batteries at the same time.
 

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Senior Member
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Load testing batteries after charging them as best possible is the only way to know for sure, one or both of the batteries may have been weakend from the faulty alternator. Alot batteries nowadays are not as stout in longevity as they used to be.


Harry
 
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