I have 2 Dodge ram vans, my 1999 computer I think broke, I replaced the alternator twice and still no charging, I tried the "external regulator truck" and it also didn't work.

So, I decided to get an excitation voltage reading in order to manually control the output of the alternator, because all I have to do is go a short distance (I am moving/ 400 miles)

Until I can get the issue resolved "automatically"

So, I soldered two leads onto the working alternator on my 01 Dodge Ram Van 1500 w/ 5.2, and here are the readings,

Yellow lead positive, green lead negative , DC voltage,

At idle, the voltage is around 3vdc, and taking a current measurement , around 1.5 amps DC current with my clamp ammeter.

As I increased the throttle, the voltage dropped, I didn't rev it too much but he voltage reached 1.5 volts. Not sure on the current as the ammeter was under the hood.

I've seen people speculate it's 12 v but it's not, it's actually 3 at idle. 1.5 amps. I assume the amps decrease as the rpm increases too.

This way, as I am driving, I can apply around 1.5v (I will get a highway speed voltage reading as I brought the wires into the cab.)

It could be a parallel number of AA 1.5 v batteries could excite the alternator just for the trip. Will update.

 

At around 55 mph, (towing a trailer) 4 speed automatic, 3.5 gears, the excitation voltage is 1.789

So, if I get a DC-DC power supply, 12v in, adjustable maybe 0-5vdc out, and a simple DC socket voltage display, I can monitor and manually adjust the output voltage of the alternator.

However, it would be good to set it at 1.5 volts, the output will be low at idle. But at highway speeds it will be normal ish depending on the display.

I say this because, if I accidentally leave it at 3v (idle excitation voltage) and I forget, and hit highway speeds, then the output could be as high as double, or even close to 28v. Best to keep it low and monitor the display, set it at highway (or towing) speed and leave it thereabouts

I assume the current drops too, so a 3 amp power supply should work fine

 

I *think* field windings are pulse-width modulated...... but, you would have to put it on an o-scope to find out....

 

Some things to check...
1. Verify there is a ground bonding strap from the engine block to the body.
2. Verify the battery cables are good and making good contact at both ends.
3. Disconnect and then verify continuity from the output wire on the alternator and the positive battery cable.

 

Ironically it seems the charging circuit in my 01 Ram Van went out last night (I haven't inspected it yet.)

I ordered a 2 pack of DC to DC converters with displays.

I think leaving the excitation voltage at 1.5-1.6 volts will keep the charging system alive, and fine tuning it while using cruise control, and leaving it at the 1.789 will yield the best results, if I set it to 3 volts (idle excitation) and forget, and hit highway speeds things could be damaged

The power supplies are supposedly being delivered today,

I got 2 with displays for 8 dollars on Amazon

https://a.co/d/011QMd7S

I will also need a voltage display for the battery, which I have in the form of a USB charger (somewhere)

 

My daily (01 Ram Van 1500) alternator went out yesterday. Voltage gauge dropped to the red left hand side. I wondered if my test leads wires were shorted but they were not.

Just got the DC buck converter power supplies. Gonna try them out tomorrow

Will update

 

I apologize , I did not see these replies !

IT LIVES

A $4 power supply got it to work:






AN IMPORTANT NOTE!!!:

Before connecting the alternator leads to the power supply,

1. Cut both leads going from the harness to the alternator field coils, leaving plenty of length to connect your leads,

2. Before connecting the output wires to the power supply, put power to the power supply, select "out" voltage, and make sure (!!!) the voltage is less than 3 volts, I started with 1.2 and slowly worked up until I saw the IN voltage start to increase!

If you are in an emergency (essentially) line myself, as I need the van to get to court, and decide if I have 3 or 6 years of life left (homelessness)

I have no reliable vehicles,

My advice is, to determine a highway speed, and adjust 14.3-2 volts at that speed (55 mph?) and do not exceed that speed as the alternator output will increase exponentially as long as you exceed that speed

ALSO, if you do it this way, the battery won't charge when at idle.

The trimpot, (voltage adjustment screw) is *tiny* and very hard to adjust if you are on the road

You *can* super-glue possibly a piece of metal to the trim pot (being careful not to super glue the pot shaft to the pot body!) and adjust it on the fly, if your situation is desperate.

Key notes,

Try and get a voltage reading on the field coil of your alternator, but you MAY be able to start at the lowest output, and slowly work up at idle until you see the charging output voltage increase,

Buy the above power supplies and keep them in your vehicle,

You may or may not want to have the wires already ran thru the doghouse, I attached the voltage input for the power supply to the SWITCHED 12v outlet

A somewhat inconvenient $4 fix for a bad alternator on these late model Dodges (late model ? Historic? Dinosaur aged?) but it WILL keep you on the road!

Also if you needed a bigly DC power supply I guess you could disconnect the outlet lead on a good battery while it is running, and push a higher excitation voltage, and get a much higher voltage, being careful not to fry the diodes (who knows what they are rated at. Maybe just stick to 14.4-5v.)

 

Another alternative, is to measure the resistance of the trim pot, from 3 volts output (idle) to 1.2v (fast highway speeds? I assume maybe 75 mph? ?)

And remove the ten turn trim pot, and install a larger easier to turn trump pot that meets those criteria, and permanently mount it somewhere so you can adjust voltage easier

A caution, if you get comfortable, and "forget" you set it to idle charge, and begin driving, you could get high 20s voltage which could damage things *unless* you intentionally turn it back down as you begin to drive

Just a warning

 

Okay so apparently the exhaust manifolds get hot enough to melt wire insulation? Who could have predicted this

So that's why my alternator went out, so I re routed the wires, and put them in an armored conduit, cut a notch in the doghouse seal,

Another thing too, it's messy but it'll work, if someone can source a 1-3V 1.5A based 12v regulator, you can wire it to the excitation wires inside, so long as you're careful to fuse them (I didn't, maybe 5a fuses on each lead at the alternator)

It would be the easiest "regulator" test and replacement in automotive history

It's like right there

 

You would need to wire the switched positive switched wire to the regulator (wiring it to an always on positive wire may drain the battery when the vehicle is not running, faster than usual)

You can use the cigarette lighter negative also for reference for the regulator

Or you could wire it to manually switched positive but why it makes no sense to do that