alternator update

It turns out i was impatient and angry previously and i think i did not thoroughly test.
My core tested good on the bench with tester adapters and manually so it is back on the tractor. But It will not self excite on its own at any rpm using a smaller pulley and the indicator light wiring method. it also will not excite if two-wire plug is removed and test light from batt to 1 and jumper from batt to 2 are used. that test method worked instantly on the bench tester, however.

If I use a wire from batt terminal to 1, it excites instantly. My sealed dash indicator light measures 30 ohms. All terminals and wires that should have voltage have same as battery voltage at times they should. if used in parallel, the test light will barely light compared to dash light.

It's almost like 30 ohms is too much resitance this time?
just guessing, the bulbs recommended in Bob M's diagrams of 200ma are 60 ohms?

I coached an I/O boat alternator wire job last year using same indicator and alternator # and it worked perfectly instantly. maybe because of difference in pulley rpm.

I do have acc light wired to ACC terminal. It would be easy to hardwire without light but I like having the light.
What will happen if i parallel a 100 ohm 10watt resistor to the indicator light? or do I reduce the ohms for that situation?
I also do not want to mess with momentary switches for exciting.

10si with warning light is supposed to be simple and reliable.
this should not be this complicated
thanks
karl f

ps but it's makin a fool out of me. The world has a smarter idiot now. nearly 140 IQ and can't make a foolproof thing work!

Your alternator is SICK... bad rectifier, diode trio, stator, or regulator.

Repair it or replace it.

Have you checked the diode trio? The original GM set-up for this alternator called for 11 ohms [in a resistance wire] for the "turn-on" voltage. I've always used 10 ohms @ 25 watts on conversions I've done. We've got a 3 1/2 inch pulley on our SMTA, & never have trouble getting it to start charging. At idle.

Run a jumper wire from the battery + terminal to the#2 terminal on the alternator & see if the alt. charges. This terminal reads battery voltage & has to be connected for the alt. to charge. # 16 wire is adequate for this.

No, it does not have to be complicated. It becomes so when you don't have all the data/info.
What model of 10SI? What pulley ratio and RPM at testing? What regulator? Was a thorough bench test done?

There are at least four different Delco 10SI model alternators - and you didn't mention which one you have. 10SI can be a #100, #102, #116, #136 and maybe more. They have different cut-in speeds and sometimes different amp-draw on the field circuit.

10SI model # 116 - 61 max amp must spin faster then 1600 RPM to make any charge current.

10SI model # 136 - 63 max amp must spin faster then 1600 RPM to make any charge current.

10SI model # 116 - 72 max amp must spin faster then 1200 RPM to make any charge current.

10SI model # 116 - 72 max amp must spin faster then 1200 RPM to make any charge current.

On the subject of field current and resistors -the voltage drop depends on the ohm-rating of the resistor, supply voltage, AND amp-draw all calculated together. A 10SI can draw up to 3.4 amps on the field circuit, but also some work fine when only drawing 1/2 amp.

I'm not trying to complicate things, but you have to know exactly what you have and what condition it is in.

If your alternator has something wrong with it, and needs as much field current to excite as your ignition coil needs to start the engine - you can't install enough field resistance to stop IGN backfeed (unless you switch it or use a diode).

The reality is, Delco 10SI and 12SI alternators are pretty simple and easy to check and fix. Takes 15 minutes to pull one apart and check everything (slip ring, brushes, diodes, diode-trio, etc.). Regulator can be checked when running via the "full-field" short-plug in back.

(quoted from post at 05:52:50 06/11/10) Run a jumper wire from the battery + terminal to the#2 terminal on the alternator & see if the alt. charges. This terminal reads battery voltage & has to be connected for the alt. to charge. # 16 wire is adequate for this.

Click to expand...

this has been done prior to post.
karl f

(quoted from post at 06:39:14 06/11/10) No, it does not have to be complicated. It becomes so when you don't have all the data/info.
What model of 10SI? What pulley ratio and RPM at testing? What regulator? Was a thorough bench test done?

.

Click to expand...

this is a freebie off of source unknown. believe it's stamped around 60amps. A new reman #7127-12 i tried behaved the same although it at least cut in at 3/4 throttle. I sure don't mind buying a new if needed since i have a core but when they behave the same I do not know which way to go.

The tester at work definitely spins faster than the tractor ever could with real world pulley sizes. it looks like at least a 4 inch drive pulley. The motor is inside the steel cabinet so i cannot see the specs. It is not variable speed and basically a volt meter with a charge light and 100s of harness adaptors. Made exclusively to decline warranty claims IMHO.

The tractor is a 400 farmall. I used a 3 inch pulley on both alternators originally. This time I used about a 2.5 inch. my previous posts were asking about pulley drive rpm and your post Jdemaris tells me the goal rpm of the alternator. the 400 drives the waterpump pulley about 1.5:1 to crank, and the waterpump in turn drives the alterator with a 4 inch pulley.

the new alternator paperwork said cut in rpm was around 250 so i don't know why it wouldn't work. I figured if the new and old acted almost the same to use the old...

thank you for your post.

karl f

(quoted from post at 23:15:29 06/10/10) Your alternator is SICK... bad rectifier, diode trio, stator, or regulator.

Repair it or replace it.

Click to expand...

I thought so, but the new one behaved almost the same! see other replies

karl f

previous posts on same alternator are:
http://ytforums.ytmag.com/viewtopic.php?p=3492649&highlight=#3492649

http://ytforums.ytmag.com/viewtopic.php?p=3502797&highlight=#3502797

If the tractor has a ACC terminal on the ignition switch, and if it will excite cleanly with 12 v no light bulb hook it up that way to the #1 post and all is well (assumes proper voltage regulation when running and charging, and no drain on the battery to speak of. >10ma.
If you need the light to be shown on the dash, it may need a new regulator.
Does the light come on with the key on and not running (like it does in a car)?
if not it will not work.

The regulator appears to be a ground to the exciter current from the key (this is what makes the light come on). When the regulator excites the alt, the terminal goes to 12 volts (thus applying 12 volts to both leads of the light).
If it will not excite without full 12 volts, no light, there is no way to make the light work. Jim

(quoted from post at 10:12:53 06/11/10)Does the light come on with the key on and not running (like it does in a car)?
if not it will not work.
. Jim

Click to expand...

light comes on KOEO like a car.
group consensus, prior experience, and wiring diagrams say it should work.
frustrating...

karl f

There's NOTHING to be frustrated about.

The alternator is simply a little "off" of "spec" and won't excite with the current you are feeding it through the lamp.

Just for GIGGLES, temporarily connect a second lamp in parallel with the first and see if it will excite, or try a 50 Ohm resistor across the lamp.

If that works, you can leave the resistor in place, ASSUMING the alternator doesn't have internal "leakage" that will drain the battery when it sits unused.

Otherwise, you need to replace the alt, or tear into it and check the stator, the rectifier, and the diode trio. If those check out OK swap in another regulator and see what happens.

OK, just saw this post... what lamp are you using... get a #194 slide-base lamp and try that. If you don't have a holder handy you can put it in the circuit with a couple of alligator leads to try it.

Does it "excite" that way?

(quoted from post at 12:53:35 06/11/10) OK, just saw this post... what lamp are you using... get a #194 slide-base lamp and try that. If you don't have a holder handy you can put it in the circuit with a couple of alligator leads to try it.

Does it "excite" that way?

Click to expand...

I am using a Dorman/Motormite/Conduct-tite/Help (they keep changing their name) part number 85938 "panel light." No manufacturer specifications listed but it meaures 30 ohm and fits a 1/2" diameter hole.

parallel wiring a test light does nothing to improve the situation. The test light barely lights (panel light is less ohms). Without a calibrated variable resistor, all I can say is that the alternator will only excite with zero resitance or no load; a full 12+volts. The test light lights normally when not paralleling the panel light.

At any rate this is a good discussion of troubleshooting and a documentary on the early stages of male balding

thank you for the help!

karl f

I'd like to see a copy of that "250 RPM" cut-in statement. That is pretty-much impossible. Might say "2500" RPM which is typical for a self-excite regulator. On a tractor with a 6" crank pulley and a 2.5" alternator pulley, the alternator would kick-in at 1100 engine RPM. 1200 RPM is about the minimum alternator RPM with a 3-wire setup. That's why those alternators are set-up to spin two to three times as fast as the engines when factory installed on cars. Typical Chevy engine idling at 800 RPM spins the Delco 10SI at 2000 RPM.

TRY a #194, and post back, please!

Thank you to everyone.
I'm going to try the 194...
and then probably take the alternator to the local rebuilder to have it built to my needs. It will avoid the experience of having an off the shelf unit not work exactly as needed.
I'll try to get a copy of that low cut in rpm spec sheet.

I can't spend much more time on this, I have my wedding in a month and much to do before then. After will be focused on the new relationship so it's like i'm runnin out of time. There were some suggestions i would have liked to try--I will get an assortment of resistors for next time.

Today i had a chance to do some digging: the bench tester spins at 1750 rpm and has a 4.5inch pulley. any marginal alternator will pass that test!

I never did any internal tests, i should learn to do those for that one day when they'll explain the symptoms.

Thank you to everyone. I hope i responded to your questions even if i did not address you directly. I appreciated all your help and found all the posts useful.

I'll let you know how it comes out.

thank you
karl f
wondering what would have happened if he went with a 10DN instead...

I tried a 194 bulb. It helps the excitement, since it is now at 3/4 throttle instead of nothing at wide open. not measuring with tach but it is also the cough/kill spot when cold...

see new post
http://ytforums.ytmag.com/viewtopic.php?t=646565

best next step for me is likely different regulator.

karl f