Pretty sure I killed the alternator. Just looking for confirmation...

[whiteboyslo]

***short version*** Truck was over-charging. Replaced the voltage regulator but had to jump it to start it. Now it's charging 13.5V-13.8V but batteries are draining FAST when sitting. Likely that I fried a diode or two in the alternator?


***long version*** Driving home from work Thursday, I glanced down at the voltage and saw it was pegged. I have a combo USB adapter / voltage meter plugged into the cigarette lighter, and it showed 18+ volts. I threw on all possible loads but could only get it down to 15ish volts. Thankfully, the commute is short (~5 miles) so it wasn't like this for long. FWIW, I've had the truck spike close to 16V every once in a blue moon over the last year, but it usually comes back down after a second or two and otherwise charges at just over 14V at idle (13.8 with loads on).

I ended up parking the truck Thursday and didn't have a chance to pop the hood until yesterday (Saturday). I replaced the voltage regulator, but I had to jump the truck (combo of a jump pack and another family vehicle) to get her started. The voltage on my handy cigarette lighter meter showed 13.8V, which I confirmed across the battery terminals with a voltmeter. I let it idle for about 20 minutes, came back, shut it down, and cranked it right back up no problems. But, when I came back a few hours later, the voltage was at just under 12V (key off), and she barely cranked but did fire on her own. Again, once running, charge voltage was 13.5-13.8V (lower than it was with the old regulator, but still OK).

So last night I left both batteries on trickle chargers (still connected to the truck) thinking maybe the batteries were just low from not charging them all the way back up. It cranked fine this morning, but by lunch was back to how it was the night before.

BEST GUESS is that somewhere in this comedy of errors I blew a diode in the alternator and now it's draining when not running. Sound about right? 3G upgrade time?

For now, the batteries are unhooked but still in the truck with the trickle chargers hooked back up. Hopefully I haven't killed them, too.

Mike

 

[pelky350]

Mines been doing something similar but with no over charging that I can remember, been on the trickle charger every other night for month now just haven't had the time to fix the problem yet, also three other alternators out back I plan on trying soon because also new voltage regulator but did not solve problem.

 

[snicklas]

One thing..... do you have a second vehicle, or is this you only ride? If it is not, once you get the batteries charged back up, leave them connected. After the truck has a chance to cool (the engine an all the accessories should be ambient temperature) lay your hand on the alternator case. It should be the same temperature as the rest of the engine. If it is warm, you have blown a diode or three and the alternator is drawing power from the batteries and dissipating it as heat.... Rebuild or replace at your leisure.......

 

[whiteboyslo]

One thing..... do you have a second vehicle, or is this you only ride? If it is not, once you get the batteries charged back up, leave them connected. After the truck has a chance to cool (the engine an all the accessories should be ambient temperature) lay your hand on the alternator case. It should be the same temperature as the rest of the engine. If it is warm, you have blown a diode or three and the alternator is drawing power from the batteries and dissipating it as heat.... Rebuild or replace at your leisure.......

Thankfully it's not the only vehicle in the fleet. Being SoCal, all it did was give me an excuse to ride the bike in. Woe is me!

I left the batteries on trickle chargers again last night (physically in the truck but disconnected) and checked them this morning. Passenger-side battery shows 12.X volts and the trickle shows it's taking a charge (not fully charged, but this is a TINY trickle charging a LARGE battery, so no surprise there). Driver-side battery shows nearly 14 volts and the trickle is showing a fault (doesn't give more detailed diagnostics than that). I cleaned the terminals real well and re-connected the clamps, but the fault is still there.

I'll give your method a shot. Should be able to tell even if I just hook up the passenger battery, yeah? If the alternator is shot, I'm skipping the rebuild and going 3G. I've been wanting an excuse to do it anyway, but wanted to make sure I didn't go through all that effort without accurately diagnosing/fixing the actual root cause.

Mike

 

[snicklas]

Yes, one battery will do. It just needs a charged battery.

 

[whiteboyslo]

So, status update....

I tried the 'check for warm alternator' method and got nothing. Putting a multimeter inline to the negative cable and checking for a current draw showed nothing as well, so my best guess is that, at minimum, the batteries are toast. A combo of being 5 years old and the over-charge probably did them in. But realistically, the alternator is probably going bad, too. I took the truck for a long drive about a week ago. The gauge never got over 13.8 volts, which is lower than what I'm used to seeing (usually 14.2). And as soon as I threw on a load, it was down close to 13.0. I let it sit for a couple of days and tried to start it, but it had lost charge again. It would crank, but not enough to turn over without a jump.

So, seeing how I'm PRETTY sure I don't have a parasitic draw (fingers crossed), I've decided to just replace everything and start fresh, which means new batteries and a 3G alternator. Thankfully Costco's ridiculously generous warranty program will cover about half the battery cost. As for the 3G, it's a topic that's been beaten to death but I may have found some particularly useful info re: alternator part numbers and wiring methods.

For the alternator, I think I found a version of the large case 130A 3G that comes ready to go for dual v-belt trucks like mine. It has the right pulley and the main plug is clocked at about 3 o'clock (from the back. 9 o'clock from the front. It will face the passenger fender once installed). Part number is 7756-3N-2G and supposedly came stock in some of the 92 E-350s with the IDI. I couldn't find one in stock local, but I bought a new one on eBay for about $100.

For the alternator wiring, I got lazy and found a guy on eBay who makes adapter harnesses on the cheap. For $20, I got a harness that has all the right connections for the alternator (including the ring on the yellow wire and the tiny connector on the white wire) and only required me to splice in the green/red wire that I snipped off the regulator harness (I had to add about 1 ft of wire to make it reach). Should make this an easy 'plug and play' job. I went ahead and pulled apart the entire wiring harness that contained the old charge cables, stripped them out (with the exception of the red/green wire, of course), and bundled it back up.

For the charge wire, I'm going to try something a little different than I've seen written. All I'm doing is taking the existing 4 ga red wire that runs from the battery side of the solenoid to the positive terminal of the passenger-side battery and attaching the solenoid end to the alternator charge post. I've spliced a nice ANL-style fuse holder into it (looks like this: http://www.orioncaraudio.com/163-211-thickbox/orfmanl-fuse-holder-single-mini-anl.jpg), so it'll be protected. I figure there's plenty of length, it's 4 ga, it already has the connection on the battery end, and the cable is still in GREAT shape (no corrosion on the copper when I cut it to install the fuse), so why not? Only concern is that the eyelet from the solenoid end is likely too large in diameter to accommodate the alternator charge post, but I can always cut it off and splice on a new one if needed.

***EDIT*** I just realized the stupidity of what I did on the charge cable. Now I don't have a cable attaching the battery to the solenoid, which will make starting a bit of a difficulty. Oops! Oh well. I'll just go pick up a pre-made length of battery cable with eyelets on both ends and connect it between the two. ***

All the wiring is done. Alternator should be here Friday. I'll post up with results and, if it works, I'll add pics and part numbers to the Tech Article for the 3G upgrade.

Mike

 

[icanfixall]

Sadly it sounds like both batteries and the alternator are bad.You have the right idea about changing all this. Many years back I was told to place a screw driver on the rear case cover at the bearing shaft. If it is attracted my magnetism its showing the alternator is working.Been many years and may be incorrect in what this magmatism means.

 

[DaveBen]

You should always show 14 volts or MORE when the alternator is supposed to be charging. 13.8 is too low and the batteries will not get charged in your lifetime.

 

[OLDBULL8]

You should always show 14 volts or MORE when the alternator is supposed to be charging. 13.8 is too low and the batteries will not get charged in your lifetime.

I kinda disagree with that.

Just after a start for a few seconds depending on how long the starting was, battery charging will be 14 to 14.5, after that it will settle down to 13.5 to 13.8 depending on the regulator setting, also depends on what RPM your running. IIRC the OEM Alt is only 95 Amps.

Sounds like you might have one battery with a shorted cell, with that, the bad battery will draw current from the good battery.

A five mile run is not long enough to recharge the current taken out from a start, especially if you have the heater or A/C on.

 

[whiteboyslo]

Got it all together last night. The alternator was a drop-in, no pulley swap or re-clocking necessary (I did have to get a M8x1.25x25mm bolt for the top mount, though). I now have 14.4V at idle, and it's completely steady throughout the RPM range. With all loads on, it's still over 14V. I didn't have to change the belt length, either.

Only concern at this point is I may want to change the fuse size. The kit I bought came with a 150A, but the alternator came with a report showing output vs RPM, and this unit can hit upper 160s no problem.

I'll add some PNs to the tech article.

Mike

 

[OLDBULL8]

It takes a God awful load to hit 160 Amps. As long as the fuse is 150 Amp Slo-Blow you r golden.

Just remember, all meters have a + or - reading, a Digital meter is most accurate.