Farmall 350 alternator troubleshooting

[riverbend]

I'm trying to get my F350 in shape to be the reliable workhorse that was my H. The 350 had been converted to 12V with a 3 wire (? Delco Si) alternator. There is an output terminal on the back and a two lead plug on the bottom.

One lead (white) for the two wire plug comes down from the output terminal on the back, goes through a diode to terminal 1 on the alternator. The other (red) comes from the + side (not the points) of the coil. The red wire (coil) goes to terminal 2 on the alternator.

The problem is that a lead for the diode snapped off. Being way behind this spring, fixing this did not come to the top of my to-do list (the H was working fine). Now...

I have been making do by touching the broken diode lead to the lead on the other side of the diode. Until now that would power up the stator and recharge the battery. That's not working anymore.

What should I be looking at to diagnose the problem ? Just bad brushes ?
Thanks
Greg

 

[Janicholson]

The wiring is wrong. The #2 terminal should be connected with a 6 inch #12 wire directly to the output terminal, no diode there.
The #1 terminal should be connected to the coil +, through a diode or marker light bulb, or a 10 ohm resistor. (series circuit through any one of those) To see if the alternator needs replaced, connect the #2 terminal as noted above, start the tractor, then touch the white wire (momentarily)where it goes into #1 terminal with a jumper from + side of battery, This should start the charging. If it does not, the alternator may be faulty from being hooked up incorrectly. Jim

 

[riverbend]

Gah. Have I ever mentioned that I really appreciate a stock system ? An alternator is nice but... Okay, I went out and checked the actual layout twice. It does look like it is wired wrong.

Grasping at straws: Aren't the coil and the output terminal at the same voltage ? If not, what would get burnt up? I might have brushes for a Delco alternator but not diodes or a stator.

Thanks Jim.

 

[used red MN]

Here is a diagram of how the wiring should go. Whether you connect the wire that feeds the no. 1 excite terminal by the diode up by the switch as shown or down at the engine to the coil feed BEFORE the resistor makes no difference. I believe overall the opinion will be that a Delco 10si alternator is just as reliable as a stock generator and voltage regulator. I myself would say it is more reliable. Sounds to me like the wiring was not tied down properly when it was installed and vibration or movement broke it. However, it may not have been wired properly in the first place.
Delco 10si conversion diagram

 

[Janicholson]

Yes, but one is switched and the other is on all the time (parked or running) I hesitate to advise the coil + being OK when some applications/modifications have a ballast resistor in them. The diode (or small filament lamp, resistor) passes 12v signal to turn on the excite circuit. If no diode (etc) the alternator will reverse flow into the coil keeping the engine running. The switched source can be a oil pressure switch from B= to the switch then to the #1 terminal. Or a push button to pulse the #1 terminal with momentary 12v. Other possibilities exist to do what the idiot light in the car does. If it charges when #2 is connected to the Output terminal and a 12v pulse is given to #1 terminal, the alternator is good. If not, it needs to be checked at an autoparts store. Jim

 

[riverbend]

I rewired the plug and nothing. Any idea what fails when they are wired wrong ?

 

[old]

When wired wrong so the excite circuit is on all the time it burn out the windings since they get hot

 

[wore out]

River, while your alternator was not wired up ''correctly'' it apparently worked for a time.

With it wired as you say, I would expect the battery would drain while the tractor was not being used, but it would not necessarily damage the alternator.

The alternator may have simply failed due to worn out brushes or other issues.

There's a link below from a previous thread with info from myself and ''jmor'' on some troubleshooting tips.

If more than simply worn out brushes, likely a local autoparts store likely will not have a voltage regulator, diode trio, or rotor or stator in stock, if they do or have to order them they are now so $$$$ at such places you will quickly approach the cost of exchanging the alternator for a re-man.

If you care to tear into it and are not in a HUGE rush, alternator parts deals can still be found on the 'net.

https://forums.yesterdaystractors.com/viewtopic.php?t=1561895&highlight=alternator++regulator

Note the test that bypasses the regulator posted by jmor.

If you get it repaired or replaced, be sure to correct the wiring involving the #1 (excite) and #2 (voltage sense) terminals.

 

[wore out]

(quoted from post at 12:42:58 06/04/22) When wired wrong so the excite circuit is on all the time it burn out the windings since they get hot

"When wired wrong so the excite circuit is on all the time it burn out the windings since they get hot"

Rich, have you EVER seen that happen?

The ROTOR windings are the ones that would be energized (the stator windings wouldn't be affected at all).

I have replaced Delco "rotors" due to worn out sliprings, worn out shaft where the (rear) bearing "rides" and due to an "open" winding probably due to vibration, but don't recall seeing many (if ANY) that looked overheated/cooked.

Yes, they alternator will get "warm" and drain the battery and certainly doesn't do the voltage regulator any good, but the rotor will be about the last thing on the list to be damaged, IME.

 

[old]

I have seen an alternator so hot that you could not put your hand on it and it stopped working at that point

 

[riverbend]

I got the part number wrong. This is a 15Si alternator but it is still not working. Checking some of the stuff in your link:
Battery voltage 13V (50V range on meter)
Output stud 12.75 V
2 12.75V
1 1.8V (10V range)
I don't have a carbon pile to check the max output.

Do you know what the part numbers are for the brushes and voltage regulator for the 15Si alternator ? Tomorrow is Sunday and at best I'll be talking to the kid who got the short straw at the parts store. If they can't look up a vehicle, they are completely lost.

 

[Jim.ME]

Did you try shorting the tab in the "D" hole to the end frame as suggested?

 

[riverbend]

I did not. Without part numbers I wouldn't be able to get brushes or a regulator today. Rummaging around in the grove, I found a Delco CS144 alternator that bolts right up. With the F terminal connected to 12V, it charges. Back at it.
I'll have to visit our local junkyard and see if they have a 10-12-15Si alternator.
Thanks for the help everyone.
Greg