High Current and Loose Wire

[divemaster5734]

Got the '90 E350 running and noticed the ammeter on the dash was maxed out so popped the hood and got some crazy readings.

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This is low idle amps. Ignore the negative indicator just had the meter set opposite to current flow for readability.

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This is above 2k RPM but not sure as I was manually pushing the throttle at the IP.
I'm guessing the alternator was upgraded at some time from stock.
Yes the batteries were a little low as I had spent a couple weeks playing with the GP and belts issues.
Then looking closer saw the white wire from the alt just hanging out in the open air.

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That's the 2nd wire off the alt connector.
I took it for a 15 minute drive at a fairly constant 45-55mph and while the current slightly decreased the draw never dropped to normal.
The charge voltage was at 15 which is also high.
Pretty sure it's something to do with the open white but not sure what to do with it.
I have 2 manuals and neither one has a freaking schematic.
Thanks

 

[XOLATEM]

Disconnect the batteries (how old are they..?) and charge them up to fully charged...They should be fairly stable and hover around 12.66 VDC...but...you will have a 'surface' charge right after charging...(more than 12.66 VDC) that you should not worry too much about...just turn on the headlights or run the radio some to knock it down. (not too much on the headlights with the engine off.)

The thing to look for is the resiliency of the batteries to stay at and around full charge after a few charge-discharge-charge cycles...

Then...go get yourself a spare voltage regulator...and figure on putting it in as a diagnostic tool...(before and after test)

Are you sure about all of your grounds..?

On the white wire..? not a clue, yet, until I go out to my truck and see if I have it...@Franklin 2 has been good about finding wiring diagrams...but other guys may pony it up, as well....

The main thing is to not panic...you will figure it out and then have yet another thing under your belt...

Hang in there, Buddy.

 

[franklin2]

Not sure what alternator you have on there, but if it's a more modern style, usually the connector has one wire that brings the alternator online to charge when you turn the key on, and the other wire is the feedback wire that tells the internal regulator what the truck's system voltage is, and the regulator uses this info to adjust the output of the alternator.

If that loose wire was the feedback wire, then that makes sense what was going on. The alternator was told to go wide open charge because there was no voltage on the feedback terminal. The regulator was trying to raise the voltage on that terminal, but never could because the wire was loose.

That also explains why the battery voltage was so high. The batteries were the only thing holding the voltage down to a reasonable level, but at the same time they were starting to cook. If you ran it long enough you most likely could have smelled a sulfur smell from the batteries. This is the reason we always slap someone's hand when they do the "pull the battery cable off the battery test" to see if the alternator is working. If all this I am guessing is true, and you would have pulled the battery cables off, the alternator was wide open and the voltage would have went well over 100 volts depending on the engine speed. On a newer car or truck this can smoke a lot of electronics in the system. With these old diesels it would have probably gotten your stereo, abs module, etc.

 

[XOLATEM]

Good golly...@franklin2 you are a smart cookie..!!!

I would have paid you well for that explanation..!!

I learn something every day here...

Thanks Guys...

 

[Nero]

Wouldn't having the feedback wire disconnected also make the voltage go full field, like 15+v when running?

 

[franklin2]

Wouldn't having the feedback wire disconnected also make the voltage go full field, like 15+v when running?

Yes, that is what it would do. It would put the full 12v battery voltage on the field for full output. I am not sure if this is what happened, just a guess. When the alternator goes full field, the battery voltage is usually higher, something like 16v. But I suppose it depends on how many rpms the alternator is turning when you check it.

 

[divemaster5734]

Disconnect the batteries (how old are they..?) and charge them up to fully charged...They should be fairly stable and hover around 12.66 VDC...

They were 12.48VDC which is about perfect.

Hang in there, Buddy.

Not much choice about it, thanks for the encouragement.

Not sure what alternator you have on there, but if it's a more modern style, usually the connector has one wire that brings the alternator online to charge when you turn the key on, and the other wire is the feedback wire that tells the internal regulator what the truck's system voltage is, and the regulator uses this info to adjust the output of the alternator.

If that loose wire was the feedback wire, then that makes sense what was going on. The alternator was told to go wide open charge because there was no voltage on the feedback terminal. The regulator was trying to raise the voltage on that terminal, but never could because the wire was loose.

That also explains why the battery voltage was so high.

It's an "old" style but probably rewound for 100A output which wouldn't require an additional belt for the dynamic resistance to generate the additional load.
I don't think it's an issue until around 160A output as I've had them rewound for 130A output without problems with slipping belts.
Found some other loose connectors inside the engine bay most likely ignored by harried U Haul fleet mechanics.
I'll get out tomorrow and trace the regulator wire.
Don't know why it would be cut and stripped but there was a lot of jury rigged stuff that I'm dealing with now.
Appreciate the input.

 

[The_Josh_Bear]

Not sure what alternator you have on there, but if it's a more modern style, usually the connector has one wire that brings the alternator online to charge when you turn the key on, and the other wire is the feedback wire that tells the internal regulator what the truck's system voltage is, and the regulator uses this info to adjust the output of the alternator.

If that loose wire was the feedback wire, then that makes sense what was going on. The alternator was told to go wide open charge because there was no voltage on the feedback terminal. The regulator was trying to raise the voltage on that terminal, but never could because the wire was loose.

That also explains why the battery voltage was so high. The batteries were the only thing holding the voltage down to a reasonable level, but at the same time they were starting to cook. If you ran it long enough you most likely could have smelled a sulfur smell from the batteries. This is the reason we always slap someone's hand when they do the "pull the battery cable off the battery test" to see if the alternator is working. If all this I am guessing is true, and you would have pulled the battery cables off, the alternator was wide open and the voltage would have went well over 100 volts depending on the engine speed. On a newer car or truck this can smoke a lot of electronics in the system. With these old diesels it would have probably gotten your stereo, abs module, etc.

Yes, that is what it would do. It would put the full 12v battery voltage on the field for full output. I am not sure if this is what happened, just a guess. When the alternator goes full field, the battery voltage is usually higher, something like 16v. But I suppose it depends on how many rpms the alternator is turning when you check it.

Just piped in to agree whole heartedly! Before I understood the system in this kind of depth I wanted to see if an alternator was going to put out the correct voltage after getting a rebuild. Started it without the alt hooked up, just to check it's charging voltage. But that doesn't work. It put out 17vdc+ and scared the fire outta me. Never to fear, after checking in on the forums I got schooled and when all put together right she was charging right and all was well.

The "feedback wire" or "sense wire" as I call it is pretty important, and kinda picky, too. You want it to be as close to the battery positive as practical. I.E., don't put it downstream of any electrical draws, it tends to push too many volts. I've tried it in a few different spots and both the fender relay or battery post worked well.

 

[Cant Write]

On a mid 90’s Oldsmobile 3800. Alternator connection on bottom, connector was broken and I did not get the “sensing” wire hooked up.

Started the car and the alternator went full field and max output even at idle. Got so hot it melted the stator to rotor and locked solid. I thought it was going to catch fire. This all took about 5-10 minutes. Had pulled the car out of a “tree row”.

 

[divemaster5734]

You want it to be as close to the battery positive as practical. I.E., don't put it downstream of any electrical draws, it tends to push too many volts.

The reg is wherever it was installed OEM, pretty sure they hid it behind a battery at the grill.
Is just another treasure hunt.

 

[IDIBRONCO]

Had pulled the car out of a “tree row”.

No need for quotes here. I understand that type of language perfectly. In fact, that's what we called them where I grew up. Where I'm living now? I haven't found anyone who knows what a tree row is. It may be because there's very few tree rows around here.

 

[Cant Write]

No need for quotes here. I understand that type of language perfectly. In fact, that's what we called them where I grew up. Where I'm living now? I haven't found anyone who knows what a tree row is. It may be because there's very few tree rows around here.

So many people from non windy areas have no idea what tree rows are!!

 

[IDIBRONCO]

It's plenty windy here too. Most of the trees are either natural and in lower places like gullies, ravines, or river bottoms, or they're planted around farmsteads. Very few people planted them for shelterbelts. Probably because this area suffered severe population loss during the Dust Bowl years. There just enough people left who wanted to plant them (again just guessing). On the plus side, it does make for some spectacular dust storms.

 

[The_Josh_Bear]

So many people from non windy areas have no idea what tree rows are!!

I didn't either until you boys starting chatting about them...but it makes sense. In my defense, I've lived in Western WA my whole life. It's not called the "Evergreen State" for nothing! Check out My neighborhood on Google Maps and zoom out in satellite view. All the green is trees.

 

[IDIBRONCO]

I didn't either until you boys starting chatting about them...but it makes sense.

They're rows of trees that are mostly planted along property boundaries and they're designed to help with wind erosion. They were one of the conservation methods that came along after the Dust Bowl years. Most of the country doesn't need them since there are plenty of trees. Tree rows are (probably) strictly a Great Plains thing. They are also good for deer hunting. The deer like to use then as travel ways. If you can find an area with food, water, cover, and several intersecting tree rows, you've found a good place for deer hunting too.