motorolla to gm 3 wire

<oops - wrong thread!>

 

ok did the "walt test" and I get no change to battery charge when touching #1 to Bat power. I'll pull the regulator.

 

Yep, some of these parts houses have an elec motor they run up the alt with. They run up 1000 rpm or so and the alt kicks in and they think all is good.

 

well ,came back from a real alt/ starter rebuilder, checked the jeep one -junk (but tested fine at the parts house machine)...checked 442 one since it was out -beautifull. since I have no money ,I pulled the jeep one apart in his parkinglot. he looks it over and said there are mismatched parts in there and things are missing , and painted ( so no ground ), so I go back home found a resistor , sanded all rebuild paint off ,got a new regulator ,and it's close to fine enough for the jeep (I think).testing to come. the light stays on till you just blip the throttle but stays off now.the volt gauge still crashes when you turn the hi beams on and turn on the heater then I'm back to 11 something volts this is what I was tring to fix.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,I am really showing my lacks in elec. knowledge,,,,,,,,,,,,,,,,,,,,,,, glad this ain't pirate ,I would have to hang myself.

 

I'm glad you're not the only one that has these kind of struggles. Thanks for sharing your story. I'm sure you've made many folks feel better about their own efforts with fixing electrical devices!

You might take picture of that alternator and see what all the experts around here think.

 

I think you should invest like $10 in an alternator and pull one from a junk yard, or get a reman one for $40 or so.

 

so if I move the #2 red wire off Bat to "sence" this load of lights and heater will the alt just kick on at idle when needed of does it olny work off idle and up?man, I feel dumb for asking these ,I feel like a newbie.lame.

this was a reman , but I have no paperwork on it to take it back , and I now have bought a regulator,brush kit for it ,I'm now halfway to another reman$$.really not an alt. problem. alot of my frustration is with all this cut into not stock wiring

 

The alternator should not kick on at a certain RPM, it should be on and stay on as soon as the #1 wire gets power. It will make less amps at low RPM and that can cause the voltage to drop a little, but it should not kick off or turn on the AMP light.

 

ok so , if I start it the light stays on till I blip throttle , then the light goes off , if you go off idle with nothing on ,the volts come up to 14,but if you start switching on things , it just drops ,

for instance at idle amp light off- 12+ volts turn on headlights , 2 speed heater I'm now high 10 volts. I thought that this 3 wire alt 63 amp would compansate for these draws.and hold it steady,if I gas it with the loads on it bearly gets over 13.7 I was getting these same readings with my old motorola 37 amp.is this as good as it gets ?

 

You can buy a kit to make the alternator a self exciter and then only have one wire which goes to the battery, the large red one (if it is red on your vehicles). Might be an easier fix. Just my $.02, hope I am not confusing the issue.

 

I think he's already tried that (essentially connecting terminal to BAT).

I still suspect a problem with an alternator component. I'm guessing the diode trio is bad since you're getting a partial output. If one of the three diodes is bad, then you won't get a full 14+ volt output.

It can be frustrating to start replacing stuff if you're not sure what's bad. Try reviewing a site like this one to familiarize yourself with what component does what, and get a visual of each piece: http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=376201

 

the trio checks fine ,I have 3 trios and all give completley different readings which sucks.
I now have the 442's alt in there and it all reacts the same ,just with slightly different voltage readings . ... MUST be how my particular jeep and it's bastered wiring . I'll try to pm Patrick on his bigger crank pulley mod.

 

I was wondering if you might try the Olds alternator!
I'll be curious to see what Patrick says about his pulley mod. When I researched this subject, I couldn't find anything conclusive.

 

Steve, how is the condition of your battery?

Have you used a battery charger? Is the battery fully charged while you have been doing the idle output tests?

Make sure the battery is fully charged via a 110v charger and retest.

 

it's good to know people , I brought the troubled alt in to the parts house I have spent thousands in and they replaced it ,no charge.

so , went threw a main curcit breaker and got rid of acouple of wires that went to nowhere, landed #2 at the hot side of breaker . installed new alt , and fulled charged battery .and all is well so heres what I have now .


at idle bat 12.45 #1 12.4 #2 12.56
at off idle bat 14.66 #14.8 #2 14.7


with load idle bat 12.16 #1 12.1 #2 11.7
off idle bat 14.87 #1 14.9 #2 14.5


so I'm happy and will figure out a smaller alt pulley or do the "Patrick mod "to crank pulley to charge at idle. and for some reason jeep runs smoother and doen't miss as much. thanks guys for all your patience.it is very much appreciated .

the pulley on the jeep is 5 3/4 compared to the 442 pulley at 7 3/8 .

 

I am still betting on the pulley, i had the same issue with a alt that was known to be a good one.

 

I've be told that high performance engines (that idle 1000 rpm+) can use a pulley drive ratio of 2.5:1 or less also it reduces load, but street engines that will idle at 600 rpm need closer to 3:1 for proper charge. I have an old tractor I converted to 12v & alternator and has a 5 in. crank pulley always needs a little gas to get it to charge but because of minimal electrical system (no lights just starter and alternator) has always worked well. jm2c

 

Glad to hear you got it working.

I had trouble with my GM alt last year. I took it to a specialist and it tested bad, he sold me a part but that didn't fix it. I ended up taking it all apart and had him test each part individually but all parts tested good. He sold me another part and that fixed the problem. Sorry, I don't remember the names of the different parts.

The good part about these GM 10si or 12si alternaters is that they're easy to take apart and fix.

 

I must have had that other one apart 15x. I tested the unit as a whole in 2 shops and it tested fine , I then took it apart and tested with a ohm meter each part and all were fine and in range as per factory manual , thats why I thought the problem was someplace else.

 

There are not many parts you can replace in an alternator. There are some mechanical parts, like the bearings, but there's only one 'consumable' and three 'solid state' items. The consumable is the brushes, which contact the rotor slip rings.

Electronically, you have the rectifier bridge, the diode trio, and the regulator. Good view here: http://oljeep.com/gw/76_tsm/Section3.pdf

Typically a low-charge is due to a bad regulator or a bad rectifier bridge. The alternator is three-phase, so the rectifier bridge converts those phases into full-wave DC. This is not filtered (constant) DC, like a battery makes, but instead the rectification of each of the phases, summed together. Each of the phases is alternating current, AC. Rectified DC is the inversion of every other wave - essentially the absolute value of a sine wave. Rectified 3-phase adds the three phases together (each 120 degrees out of phase with the next) to get rectified DC with an average value of around 14V, but with a lot of ripple. If you lose one of the diodes in the rectifier bridge, the power to the output will drop because one-half of one of the sine waves for one of the phases will be lost.

The regulator will never see this as long as the battery is up, because it takes its reference voltage from another set of diodes, the diode trio.

The old Motorola alternators were terrible about this - they'd pop diodes often, which makes the output weak but looks ok to a meter. If you were to 'scope it, you'd see it, but a meter averages over a long time compared to the alternator phases