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Alternator or glow plug problem?

10K views 10 replies 5 participants last post by  Jakl 
#1 ·
2006 F250 6.0

A couple days ago immediately after starting I would get a battery light, but it would only last about 5 minutes.

Yesterday I installed an Edge CTS2 and saw that my battery voltage would hang out around 11.5-12.0. After about 4-5 min of operation the voltage jumped up to ~13.0, with it peaking out at around 13.4.

Does this sound like a bad alternator or bad plugs that are drawing too much power?
 
#2 ·
Sounds normal. Actually may be a volt higher than some trucks at start up. As long as the glow plugs are on, it draws that much power and voltage will drop until they go out.

I would guess the light means an alternator. You can bring it in to an Autozone to check, but be cautious. I don't have a whole lot of confidence that each employee can check dual battery trucks or that the tester is really rated for trucks with our power requirements. The alternator is the easiest part on the truck to pull. There is a trick to getting the belt off of a little catch lever on the tensioner pulley.

Could be a good idea to keep monitoring the voltage. The battery light did come on for a reason. Last year, sitting in the cold, my truck would turn over slowly. I kept checking the voltage and pulled the alternator and brought it to the store, but checked fine. This year it does not do it. The only difference is I took out the factory stereo and installed HID lights. Same batteries, starter, and alternator. Works good this year. Batteries are now three years old.
 
#3 ·
If you have dual alternators, your primary alternator may be bad. The secondary alternator is not energized until the glowplug relay is turned off so the glowplugs aren't damaged from excessive amperage. The primary alternator should be charging as soon as the engine starts. You may only get 11-12 volts, but it should be enough to turn the charging light off.
 
#4 ·
Had the alternator tested. It is in fact the voltage regulator. I went a picked up a new (not reman) from O'reilly but it is only the stock 110a. Truck is bone stock minus an EGR delete, tows occasionally, and I don't really have plans for any sort of aftermarket stereo or lighting (maybe reverse lights in the future and some upgraded speakers, but nothing crazy). Is this 110 going to do just fine or should I look at upgrading to a 140 or something?
 
#8 ·
Got the alternator in today. Went to install it and it seems to need some sort of adapter to make it fit the factory harness (voltage regulator).

The 2ga wiring upgrade kit only came with one length to go to one battery, but from the factory the harness goes from the alternator directly to both batteries and then has a bridge between the 2 batteries as well. Do I need to leave one unplugged and just run the alternator to the passenger battery, and then leave the bridge connected?
 
#11 ·
Looks like there is another that goes directly from the alternator to the drivers battery as well. Perhaps I'm mistaken. What bolts to the top of the + cable on the driver's side?

On the passenger side + terminal there is a post with a nut on it. That seems to be the + cable to the alternator. What I cant tell is what the identical post on the driver's side goes to.
 
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