motorolla to gm 3 wire

heavy iron and ericm have been helping me make the switch. I suck at electric and have bugged them a bit,,,,,,,,,,, but my wiring is cut up and FAR from stock. the 3 wire alt will charge and holds a steady 14+ volts , but at idle the amp light is still lit with the motor running and not charging it takes quiet a bit of off idle gas to throw the alt on and the light goes off at the same time. I made a schematic but don't know how to post it here , I have to turn a ign switch then push a button and there is a master kill switch and circuit breaker in there too. BUT ............. #1 to amp light grey wire ,#2 red wire is going to BAT on alt (for now) (should goto the main cur breaker))) and BAT wire goes to battery. why won't the light go out? what do I have wrong ?.


I have found lots of cut wires ,exposed, no insulation , no solder , just twisted together and green and the use of bandaids for tape. looks like the po was electricly challenged . I now have most of that fixed

 

I'm doing a similar upgrade to mine now. One thing I haven't determined is if the stock resistor/diode is suitable for the bigger Delco alternator.
This diagram is pretty basic: http://www.jalopyjournal.com/forum/showthread.php?t=260412

It might be a good idea to overhaul your wiring and start from scratch, too.

 

stock resistor/diode is suitable ,,,,, I don't think I have one . I have no speedo gauge just a amp light, in the speedo cluster hole I have a B-29 Gyro.

and all crapped out wires have been replaced.

 

crankshaft pully size comparable to the application the alternator came off of?? if its smaller it wont turn the alt as fast

 

same size, 2 1/2" just like the motorolla . I had to buy a double v pulley since I run OBA off the alt.

oh ,just reread your post Kasier ,I don't know crank size application .......it's #7127 62 amp.

 

I ran the #2 wire up under the dash and hooked it up to where all the power feeds all the applications, that's where I felt it could sense what was happening at the power distribution point and respond accordingly.
Once you rev it up and the amp light goes out and it comes back to an idle does the lamp come back on? Also didn't you rebuild this alternator? Could it be that there is still some kind of fault in the internals of it keeping it from kicking on sooner?

 

Sounds like the alternator isn't turning fast enough at idle.

Won't a smaller alt pulley make the make the alt turn faster?

 

Once you rev it up and the amp light goes out and it comes back to an idle does the lamp come back on? -yes - idle is set at about 750ish .no charge or light goes out till about 1000rpm.

had it checked at vato-zone and they said all is well ,inside.........

eric- they don't make a smaller diam v pulley .didn't Pat make a bigger diam crank pulley off a 350 buick?(with a hack saw or nail file?)

 

What is the diameter of your crank pulley and your alternator pulley?

 

With the grey wire from the Gen/Alt light going to term #1 on the Alt and the other grey wire at Gen/Alt light going to the ign switch HOT when ON, the alternator excitation circuit is correctly wired. When the alternator is charging, you need to test the voltage coming out at term #1. That voltage will usually be a little higher than or at least equal to the Bat term voltage reading on the back of the alt. If it is not, then your internal regulator is bad.

 

Just for info my crank pulley is 6-3/4" at the rim and the alt pulley is about 2-3/4" at the rim. Different motor I know

 

I really don't think this is a pulley size issue. I suspect there is a component inside the alternator that has failed (or partially failed). Rebuilding Delco alternators is easy, straight forward and costs around $30 (and that's the kit that includes bearings).

If you disassemble the alternator, make sure the stator crimp is good. The factory just puts a clamp around three coated (insulated) wires and expects the clamping action to disturb the coating enough to establish continuity. I finally took my 'new' alternator to a repair shop because I could not get it to work. He had the thing fixed in a few minutes, but of course he new what to look for! He removed that clamp, cleaned the wires, soldered them and re-clamped them.

 

Steve,

What is the voltage at term #1 at idle?
What is the voltage at term #2 at idle?

 

BAttery at rest 12.62
Idle , light on #1-2.45 ------------------high off idle, light off - #1 -14.8
#2 -11.98 ----------------- #2-14.73
Battery check at post -charging 14.67

understand?

 

did u say it was a gm 3 wire they have an exciter that meeds to be hooked up to a + ignition souse bu you probly all ready know that also might be the alts regulator just a thought sorry if im repeatin n e 1

 

Yes, I'll check mine this weekend (if I can dig it out of the snow)

 

I no workie today , the 442 has the same alt,(only polished) , so I will flip things around.and check things.

 

Do the #1, #2 terminal voltage test too. The polish is probably good for 1/2 a volt too.

 

That #2 -11.98 should actually be the same as battery at rest 12.62. As a test I would remove the wires to #1 & #2. Make two short jumper wires and connect #2 directly to the Bat terminal. Plug in second jumper to #1. With the engine running at idle and your volt meter connected to the battery, temporarily touch the loose end of wire from #1 to the Bat term on alt. The alternator should begin to produce the proper output 14.8 or so. This is to say that the wire from term #1 does not (repeat not) have to be connected all the time to a source power. It is only used for initial excitation to help the alternator build the required magnetism in the rotor. The alternator should continue to produce power at idle 650-750 (even less) until engine shut down. If this does not occur then the regulator is not functioning properly. (It's broke).

 

walt -I will have to read that about 5x.

edit ok got it , I'll give it a go before pulling both vehicles apart.