Anyone have any ideas for me? 2001 super duty, 7.3 w/ambulance package (I'm assuming because I have 2 alternators)..... Last night the voltage meter in truck was jumping between normal to high and then pegging up over 18 volts. Then, magically it quit and was fine. Got in it this afternoon and it started again so I stopped by Advanced and had them test the system. Cranking was normal but the charging system shows high voltage. 16.22v/15.4 amps w/no load & 16.23v/44.6 amps w/load, 112mv ripple (what the hell do potato chips have to do with this?). That sounds a little high to me but......what do I know. I'm hoping someone here may know.

Anyway, pulled the top alternator and took it back and it bench tested at 14 volts w/.8 ripple so they said it was fine. Then we pulled the bottom one and tested it and........guess what?! 14 volts, .9 ripple! So according to them, neither alternator is bad but combined they're bad. They have no answer as where I might look next. I did some reading on here and found mention of some type of switch or something that switches back and forth between alternators somehow but can't find details. Could that be the issue and if so where do I find this.....relay/switch thing?

Please, if anyone has any info that would help I'd really appreciate it. I was supposed to go look at a camper today but that 'taint happein' now.

 

 

I took both alternators to 3 different stores to be tested since all the garages were closed on Saturday afternoon and all 3 had the same results. Both tested at 14.something amps output and passed. Now how they can both produce 14. on their own but produced 15.4 up to 44.6 in the truck running is beyond me but...... The odds of all 3 having bad test machines or stupid operators has got to be pretty slim so I'm not convinced that just replacing them is the right step. If even one of the shops had a different result I'd have a different opinion. There has to be somewhere else to look.

Anyone else out there??

 

 

as He Stated...

do one .. then the other... an remember both must TALK to each other... or else issues..
and grounds... good grounds are NEEDED so alternators know what ZERO / Ground is...... both must have good grounds and good wiring ...

a 30 second test is use-less with this problem... even 3 stores is more use-less...

18 volts.. even 16 volts.. = bad regulators or bad grounds. on one or both

 

Mine has a sticker that specifically says it is NOT an ambulance prep package. I would think that a 350 chassis cab could be one but I don't remember seeing any single rear wheel ambulances that weren't van conversions.

If checking the grounds doesn't solve the issue it sounds like the voltage regulators. When mine went bad (low voltage) I replaced them both just like I do with batteries. It is super easy to replace the upper alternator but super NOT easy to replace the lower.

When I got new ones they came with a ground bolt (the OEM alternators have this hole/mount on the back of them too) and it was recommended to run a cable from the case to the negative terminal of the battery. Something to think about.

 

Where is said sticker? I'll check on mine but yours has 2 alternators and is NOT an ambulance pack? BTW-mine's a CCDRW

 

Ok.....aren't the alternators grounded through the mounting bolts or is there another cable somewhere? Cleaned and tightened the battery grounds and everything else looked ok. What/where are these other grounds to check?

After we had put everything back together everything seemed fine...oddly enough...and we've driven it a little bit but tonight I started down the interstate and got about 3 miles and the ABS light came back on and needle jumped to 18 volts again. This time I found that if I dropped it into neutral and let the rpm's drop the lights would go out and the needle dropped back where it's should be but as soon as I throttled it over 1000 everything went screwy. I do hear something either under the dash or outside the firewall clicking, like a breaker would sound, when things drop back to normal. I unplugged 1 alternator but it made no difference. Brought it home and parked it. I guess 2 alternators are the order of the day ?

 

Too bad this fellow didn't come back and tell us what the cure was ```

 

I thought I implied it but maybe not, I put in 2 alternators. No sense in fixing one and then having the other one cause a problem 2 weeks later.

 

Thought I would add that normal for most ford trucks is 14.4 or so. I have a ambulance regulator that does 14.7..volts which works well with plow /winch/ extra lights etc.

 

Same thing happened to me, mine was a bad pigtail on the alternator, check your pigtail for burnt spots , or if the clip is broke on it, might have to splice a new on in. my issue was over charging, and undercharging

 

For grins, measure it sometime when it's well below Zero and see what you get. Battery and charging voltage chart specs are normalized for 70° F, the "correct" charging voltage is always a moving target, in cold weather the battery resistance increases so the charging voltage needs to be higher.