Looking for information on Truck Battery & Alternator...

I am having a concern with my 2006 F250 6.0 Diesel.

The battery light comes on and I am not able to figure out why. So I need someone to follow through on my thoughts. My truck is not chipped or programmed. I have a electronic gauge set that shows a lot of information from the computer. I can select any number to show up on the set of gauge.

The battery light is comming on at low speeds or if I am sitting and idling. When I take off and drive at highway speed and in most city speeds the battery light will go out after a while, but if I stop for a couple of minutes it comes back on. On 9/30/11 I had a set of Ford batteries installed that have the 100 month warranty for $239.00. I was in Oregon it was the best place at that time where I could get the batteries.

I took my truck to the Ford Dealer in Bangor ME and they tested it out. Said the Alternator was good and the battery tester said the batteries were good but needed to be charged. I took the truck back to the campground and put it on trickle charge (2amps) for about 6 hours (per the dealer's suggestion). Took the truck out again today and still doing the same thing. I put the battery charger, 10amp setting, (smart charger) for a couple of hours and the battery charge shows 13.4. Well it still goes down.

I don't want to jump out and buy new batteries because the Ford warranty replaces them for free for the first three years. I can't tell if the alternator is bad because it does charge the battery up while driving but doesn't keep it charged when going slow (15mph through state park) or idling when we stop for a few minutes.

Any one have an idea?

BC

BTW.. We plan to leave on Tuesday so I can't leave the truck at the dealers. I have reservations at a campground in Vermont on Friday. I believe it will make the trip so I am not real worried. I would just like to get it working correctly.

Sounds like you need to have the alternator checked by someone that can do a proper load test.

I agree with 'porthole' as to having someone do a load test on the alternator. You can do a preliminary check with a DC volt meter by turning on the headlights and A/C with the truck running at about 1000 rpm. If the batteries are need of charging, the alternator will be putting out about 14.2 volts. If not you probably have a bad 'diode' in the alternator that is limiting the alternator's output at low rpm's.

Bob,, this is almost unheard of on the units with the serpentine belt, but if the tension of the belt is not correct it will not let it charge at low rpm's. The belt is actually slipping. It takes a lot of power to pull the alternator. Check the tensioner pulley and make sure it still has travel and it is not at the end of it's travel. If at some point the belt has been replaced it could be a little to long and the tensioner is at the end of it's travel. We used to find more loose belts than bad alternators.

If belt and tensioner are OK.. then I go along with (Jim) 57chevyconvt. 1 bad diode and it cuts charge rate by 33%.

And now days in the modern world we live in.. they don't replace the 1 bad diode for $5 and $75 labor.... no,,, no... new alternator..$300 plus labor.

Jim M

I agree with Duane check the alternator and do a load test on each battery one may be bad.

Bob,

I would bet money your alternator is starting to go! However the advice for checking the belt and tensioner are excellent, tensioner pullys have a huge failure rate.

Good luck and thanks for turning me on to this site, back in the summer of 2011, I pulled into the American Heritage RV park with my brand new Sundance fifth wheel, you cornered me before I could get out of the truck LOL, thanks!!!

Brian

Bobcat, get a new dually!!!

I would charge the batteries and then have them load tested. It is very possible to have a bad battery. If you have true battery defect, it shows up right away. If you have a multi-meter, you could check the alternator output. You also should check the battery connections. As other have mentioned, you should check the belt and tensioner. Belts only should be replaced at 50,000 miles.

Jim, as to why a shop will replace the whole alternator and not just brushes or a diode, a warranty will cover the labor of the shop to replace it. Also when the shop just fixes one diode and then next week the brushes go out, then the customer is at the repair counter saying what crap work the shop just did, all while there are two other customers the shop is trying to sell to. That doesn't reflect well, and the shop's reputation goes down. Ernie

First things first. Clean the terminals with a terminal brush and baking soda and water. See if that solves your problem. Been my experiance that corroded terminals can and will decrease charging at low speed and idle.Check the water level. Then charge 'em up and see what happens. After that it's time for the load test. Let us know how you make out. ED

bighorn3370 said:

Jim, as to why a shop will replace the whole alternator and not just brushes or a diode, a warranty will cover the labor of the shop to replace it. Also when the shop just fixes one diode and then next week the brushes go out, then the customer is at the repair counter saying what crap work the shop just did, all while there are two other customers the shop is trying to sell to. That doesn't reflect well, and the shop's reputation goes down. Ernie

Click to expand...

Warranty used to pay only for repairs needed, you only replaced what was defective. Now things are a little different on individual components, cheaper to replace the complete component most of the time because most of the techs now days would not know how to do it and it's not worth the comeback problem.
I speak from experience, 34 years as GM service manager. Hands on type, not office duty.

Jim M

Ther could be a ground problem. When ther is a reacuring battery problem I usualy check it. On my 2005 SD the battery ground from frame to engine on the passenger side has broken and for 4 years I was only charging one battery the the lower battery would drain the good one. There is a ground strap that bolts to the engine from the frame in the very front right corner of the engine.

The driver side battery is also just grounded to the frame and that connection should also be checked out.


In the Ford forums its been addressed many times.

But there is no garranty it will solve your discharging problem, are you able to see the running voltage of the system. Mine runs at 14.2 Volts when the batteries are low when started and 13.6 Volts when fully charged.

The dealership checked the alternator and the battery. Alternator was said to be good and the Batteries just needed charging. The thought about the serpentine belt is a good one. I had the fan clutch and sensor replaced last time I was in Dallas area about the first of the year. I will have that checked out. The terminals are clean. Checked by me and the dealer. I charged the battery yesterday evening for a few hours up until 11:15 PM. This morning the I checked the battery and it did not discarge overnight. Was about .2 volts lower or less. It does not seem to get below about 11.7 or 9 volts and going down the highway the battery light will go off and the voltage is about 13.9 volts. The idea about the serpentine belt is a great idea.

Thank you, I appreciate your input.

BC

I forgot to mention it, the alternator or alternators if 2, do not load till the fuel heater cycles out and weak or discharged batteries will show low voltage till alternator kicks in. But on my truck I never see any lights just my digitasl gauge showing lower then 12 Volts

All good suggestion have been posted. However the battery lite normally does not have anything to do with battery charge. Its telling the driver that the charging rate is low. Normally you have an alternator that is failing. Bob, I'm surprised that your truck does not have a volt or amp meter...just an idiot lite.

Something to consider. You can't check an alternator without a proper load test. You can still a god voltage reading with bad diodes. You just wil not have any current to actually charge a battery.

Bob, your comment about not going lower then 11.7 going down the highway - that voltage is essentially a dead battery

Hello. I have a 2004 F250 PS and I just replaced my alternator in my rig. If you remove your alternator and take it to Oreillys/Kragens they will test it for free. You can also take it down with your truck and they will test the batteries and the Power modulator for free. I replaced my alternator for 143.00 bucks plus I rented the serpentene belt de tensioner for 31.00 bucks. The guy at Oreillys also stated that if you alternator is working then you might have a problem with the fuzable link. David.

The fuel injector control module could be damaged so get it fixed asap. Its one of the problem with our 6-0s.

Sent from my GT-S5660M using Tapatalk 2

Service Manager of Darling's Ford in Bangor Maine called me yesterday and was not happy that the problem was corrected. Asked me to come in today and see what the problem could be. He drove it around and saw when the battery light came on and we are now in their waiting room to see if they can find the problem.

More info later.

BC

Update:
They are going to replace the alternator. Why didn't they do it the other day when I was having it check out. I am glad the Service Manager called me to come back in. Good business sense.

Later
BC

If you can't get it working right after all the good suggestions above then take it to a shop that specializes in fixing alternators and chasing down electrical problems. We have one here in Boise that I took the alternator from my boat to. They did a check on it putting it on a running bench and virtually eliminated all problems with it. Turned out to be a wire up in the cockpit had come loose. I am sure most towns have a shop like this and it is a lot cheaper than paying for a new alternator.