(Sorry folks, this is going to be long) I just got back from a 3300 mile trip from San Diego area, through Seattle, to northern Idaho, and back. I love my Excursion, it was a great ride, and the engine ran beautifully. For the record I got 18.75 to 21 MPG (calculated) the whole way. Now the problem: After we gassed up, on our way out of town, the batteries were too low to start the engine, and I had to get a jump from someone. We left anyway!!! I had no further problems the remainder of the trip, and drove a great deal at night, with air and radio on, etc.

I have been having this problem off and on for several months now, and am not really sure what the problem is, so let me try and lay it out. This only seems to occur if I start the Ex. and move it across the street and back 4 or 5 times (as I do when I have a project going on in the driveway), or maybe run up to the store a half mile away once or twice in there. Now, I know that these take a lot of “juice” to start up, but I just don’t recall this ever happening before 6 months or a year ago, and my habits really haven’t changed that much. Because of this, I am searching for something that is just not quite right.

I did some tests today, and would like some opinions and suggestions. I tested the voltage of both batteries before beginning, with everything still off. Got 12.62 on the right battery, and 12.63 on the left battery (here I am designating right and left as MY right and left as I face the engine compartment from the front of the car). I then started it, drove for 15 minutes with air conditioning and radio on, and left it running while I re-tested the battery voltages: Got 13.76 volts on the right battery, and 13.79 on the left one.

Then I tested the voltage to the “battery” terminal on the alternator, and got 13.86 volts. By this time, the left hand battery was measuring 13.82 to 13.83 volts. With the engine still running, I turned off the air conditioner and radio, and about 1 minute later measured the battery voltages at 13.82 on the right, and 13.84 on the left. Turned the air and radio back on, and the voltages dropped to 13,61 (R) and 13.66 (L). Next, I had my wife rev it up to 2000 rpm for a couple of minutes, and I re-measured the voltages at 13.70 (R), and 13.76 (L).

Now, I shut everything off, and tested the battery voltages to be 12.82 volts in each. I load tested both batteries, and the right one dropped to 11.91 volts after 10 seconds, while the left one dropped to 11.90 volts. After resting, both batteries now measured 12.75 volts. This would seem to indicate that my batteries are healthy... Right? They are, by the way, 2 years old at the end of this month, and are “original” Motorcraft batteries (850 cca) purchased at Ford.

I guess my question here is, shouldn’t, at least at some point, my “running” voltage be between 14 volts, and 14.2 volts? Does all of the above possibly indicate a voltage regulator problem within the alternator? And if so, has anyone else tried rebuilding their own alternator and replacing the internal voltage regulator yourself? I really hate to start the inevitable cycle of going thru rebuilt alternators if all I have is a voltage regulator problem. Also, to be honest, $350 - $500 for a really good aftermarket unit is going to be a bit tough for me right now.

Thanks for the help!

 

Did you separate the batteries to test them since they are connected? Also, a simple voltage test won't really indicate a batteries health. They must be load tested separately. Alternator output sounds "OK" The good thing is that the motorcraft batteries have a 3 year free replacement.

 

NO, I did not separate them... Thanks for the heads up! I will do so, and re-load-test in a few minutes, and post the results. Really appreciate you catching that! Mike

 

Your alternator output sounds "ok". If this car is not your daily driver you can do the following. Disconnect both batteries (both grounds first) and remove from the vehicle. Give them a thorough cleaning and along with that clean the battery clamps and check cables for corrosion. Check grounds also. Break and re-make the nut on the output lug (big wire attaches to it) on the back of the alternator and check the three-wire plug also...maybe spray with a little contact cleaner. The above are just maintenance type items...your voltages and voltage drops don't really give an indication of trouble. Place batteries on your workbench or a table and check cells for proper electrolyte level...add distilled water only and do not overfill. Then charge batteries overnight with a 2 amp setting (individually), or charge them in parallel (both connected + to +, - to -) at a five amp setting on your charger and load test after that. How are you load testing? You could also check the specific gavity of each cell after the batteries are fully charged...but the load test should tell you what you want to know. Hope this helps.

EDIT: When you re-install the batteries connect the positive clamps first and the grounds last!

 

OK, re-load-tested batteries, isolating each first.... Right went from 12.80 t0 11.56, and left went from 12.81 to 11.61.

So, are the voltages that I got in my first post (not counting the load test) pretty normal for these engines, or at least with the stock alternators? They don't commonly run at 14.0 to 14.2 volts?

 

Most of these Ford alternators I have seen will put out about 14.0 to 14.2 volts when they are cold...no lights and accessories running. When they are warm they are usually around 13.6 to 13.8 volts...no accessories running. With a diesel the alternator will not be at full output right away because of the glow plug timer. While the glowplugs are on the alternator output is reduced to protect it from high current demand. Starting and stopping the engine repeatedly without ample run time to recharge is depleteing your batteries. Again...how are you load testing?

 

Actually you have NO alternator output on start-up when the glow plugs are on.

 

Thanks Jakebrake. I am using an SPX load tester that I purchased (suggested by BISMIC) last time I was having (unrelated) problems a couple of years ago. Isolated each battery the second time, and load tested for exactly 10 seconds per instructions.
On your other suggestions, as far as cleaning terminals, battery posts, etc, there is not much need. Everything is extremely clean, as I actually wash my entire engine several times a year. ( yea, I'm kind of a fanatic) I visually checked all terminals, and they are all very clean. I also compared voltages at the "battery" terminal on the back of the alternator to the battery voltages at each battery, and they are virtually identical. So I do not think that there is any connection problems, etc...

 

Hey Mark, great to hear from you! Hope you, your family, and your truck are well! How long does the engine run before the alternator kicks in???

Is it possible that what I am experiencing is completely normal, and I need to work on NOT starting it and moving across the street and back several times in a row?? Is this just something that you don't do without charging them??

 

Hello Mike - hope all is well w/ ya! Sorry you are having issues, but I bet it is only the batteries (hopefully anyway). Things are good here - I am almost paid off on the truck, but only 2 weeks more of warranty! It is running good though - soon to have elective surgery (studs).

The alternator will come on when the glow plugs turn off. I don't know the formula that the PCM uses for the glow plug "on" time. It varies and depends on several parameters.

Get Ford to load check the batteries (they have better equipment than us DIY'ers). They should do it for free since they are Ford batteries and under warranty (should still be under warranty). I like my load tester (and have diagnosed a number of bad batteries with it), but it tests at lower amps than what Ford's will.

I would get a battery tender if you are ONLY going to be making short trips. The last thing you want to do is fry the FICM. However, if you are making a couple least one fairly long trips on each tank of fuel, you are probably OK.

 

You are probably right as far as the connections go...like I said they are just good maintenance type items. Be aware though that battery posts can look clean and still not provide a good connection. Always good to disconnect periodically and brush both the post and the clamp with a battery post/clamp tool...especially in instances of high current demand from the batteries. Sounds like the load test is ok. Good luck.

 

Does it actually go to zero...or is it just greatly reduced? I stand corrected!

 

2003 Excursion,
If you don't have one of the newer good battery chargers they can be had for about $50...at Walmart even. The newer smart chargers will actually do a better job of charging batteries (compared to older types) and extending their life. They can also desulfate batteries that have sat for prolonged periods while at a poor state of charge. Just something to think about...good luck.

 

Mine measures zero at first w/ my inductive ammeter. I am pretty sure that the single alternators only get an on/off signal from the "I" circuit - no variable control.

 

My guess is that for all practical purposes the output is zero...I just would not think that the output would be "zero"...maybe very little...but not "zero". Inductive ammeters do have some limitations...thanks for the info! I will have to see if I can find anything on this...just to satisfy my curiosity...and waste a little time.