Okay, here's the story. I've had no problems with starting my 2000 PSD until yesterday. It was 85 deg. on wednesday and 40 deg on thursday and after being parked all day thursday, it wouldn't start. I got it jumped this morning and drove to Checker where it died as I was parking. No juice left, not even enough for the dome light. I figured the fuel pump ran the batteries dry on the drive over. Pulled both batteries and they both tested fine and they recharged them. Once re-installed, I started the engine and they checked the alternator. The display said "Charging System Problem". The alternator gauge reads okay and I put my multimeter on the alternator while running and it's showing the requisite 14 volts. Is there a relay or something else somewhere that would cause the alternator juice not to make it to the batteries? Could a drastic change in temperature affect something? Thanks for any help.

-Charles

 

You may be getting 14 volts but what amperage is the alternator putting out?

 

This happened to me way back in September. I'm almost sure your batteries are no good. I had to replace mine after two years of faithful service. Just have autozone or anyone who can test your batteries for you, check them out and you'll know all you need to know in order to make the next move. You can probably just have them replaced under warranty if your vehicle is less than 3 years old. That's how I got my new batteries. I hope this helps.

 

Thanks for the replies.
I did have Checker/Kragen test both batteries and they both tested to be just fine.
I don't have an amp meter but am sure I can borrow one. What amperage should it be putting out?

 

We took a long trip 5000 miles in a couple of weeks, shortly after we returned the truck stopped starting the shop replaced both batteries and alternator, 9 months later we took a similar trip and now the truck again has stop starting unless I charge the batteries, I don’t know if the alternator is working, currently I don’t know how to check for that, but the gages seem ok. This is a 2000 X, I used a voltmeter and it read 12.58 I have a 97 f350 Diesel and it starts fine when the volts read 12.0; does anyone have any idea’s?

 

An update. Had the batteries tested again at another auto parts store. Again tested to be in perfect shape. Put the multimeter on the alternator again and it was putting out 11.88 at idle, not 14 like it should, but it would occasionally spike up to around 14 for a few seconds at a time. Tested again this morning after driving to work and was putting out 11.82. I'm sure now that the problem is the alternator but what could cause this fluctuation? Is there something I can fix or replace in the alternator or do I have to replace the alternator?

 

When I first had my alternator replaced it too spiked a couple of times before failure.

I hate replacing parts without knowing why they failed; I hate the thought of having to replace my alternator every time I go on a trip or 9 months.

 

Just noticed something that should have stood out before. I hadn't even realized that the alternator idiot light is not coming on when the engine is running. I know it works because it comes on when I turn the key but once the engine is running, no light. So, if the alternator is charging 11.82 volts and that doesn't go up when I turn lights on but the alternator light does not indicate a problem, could it be the fusible link? I'm thinking the idiot light takes its queu directly from the alternator so if it's okay, no light; but if the fusible link is out, no power to the batteries. This make sense?

 

This is alarming fact. I also have no indicator light of alternator failure. If it was the fusible a link it I would think there would no power at all. Also when I first turn on the key the gage reads 20% once the started and running, the gage reads 75%.

My fear is that it’s something to do with the computer having control over charging, I could be wrong on this but it seems one of the features of the Auxiliary Idle & PTO Control unit was dealing with charging batteries; wouldn’t this carry over even to Excursions.

I think the next step is to pull the alternator and check.

 

The internal regulator in the alternator may be no good. One time I went through 3 alternators before getting one that worked correctly.

 

I too just replaced the alternator, prior to this repair the idiot light came on and the ampmeter appeared to be over charging (around 17 amps), replaced with napa alternator with lifetime warrenty 218.00 and free tow deal.
Oh by the way, easiest alternator I ever replaced.
Ed

99 F 450 crew cab 4x4 landmaster body

 

Do you mean 17 volts? The gauge on the dash is a volt gauge.

 

Ok, first a few facts,
The voltage output of the alternator is a wire going back to the battery. I don't know the exact route, it could connect at the battery side of the starter solenoid, most likely.
The amount of voltage the alternator puts out is dependent on how much current it is putting out. I don't know the exact voltage the alternator will put out when it's pumping out full rated amps/current but in my experience, a severely drained battery or bad battery, which will suck a lot of juice from the alternator, results in only about a volt max of drop as compared to when the alternator is charging a good/charged battery.
So, with your headlights on and fan on high speed, you should be able to measure 14.5 volts at the battery. If not, try this:
With the engine running, pull of the negative battery lead of one battery and measure the voltage at the other one, if the voltage goes up, the battery you disconnected is bad. Try again with the other battery.

I don't know about the computer controlling the amount of alternator output, that sounds rather outlandish a design for an auto maker.

The idiot light isn't the most trustworthy. I'm not sure exactly how they are connected in but you may have to go pretty low before it comes on.

The only thing in the alternator, besides the regulator, that could cause a voltage spike would be if one of the carbon brushes was making momentary contact. Not likely in a new alternator but likely in a well used one. Spikes most likely due to the internal regulator as stated.

Check the wiring harness and connector that plugs into the alternator and make sure everything ok there.

I have never seen a fusible link in any auto power schematic I have looked at, between the alternator and battery. The regulator is the primary source of protection.

I haven't had to work on any of my Power Stroke alternators and it sucks to hear that the regulator is internal and not serviceable. Just another way to get more money for parts replacements I guess.