Question: Replacing the alternator

[Evolution1980]

Hey everyone...
While attempting to reconnect my battery, I think I fried my alternator's electronics. I was having a difficult time getting those damn side-terminals to connect and I was arcing pretty good. Eventually I got the connections secure, but then noticed that my battery light was full brightness without the key in the ignition.
I got the car started and the battery light went out. I wasn't getting any charging voltage (+ ~2v) at the battery. Shut the car off and removed the key, battery light came back on.

(This may be an irrelevant part of the story, but in case "details matter"...)
I restarted the car and left it idling for maybe 10-15 minutes with the hood up. Came back out and smelled something unusual and noticed a faint smoky haze. Immediately shut the car down and it proceeded to diesel like a mofo. I noticed my alternator and MSD ignition were hotter than I think they should've been. But that's just speculation that they were hotter than what would be considered normal. "Hot" being, "It probably would've burned my fingers if I had kept it on there," especially the alternator. Also, there was a lot of black residue on the bottom of the pulley side. Was it always there? I don't know. Maybe it was and I never noticed it. Or maybe that's fresh from whatever potentially went kablooey?

So I took the alternator up to an Advance Auto Parts and an O'Reilley's for a free bench test. Both of them said my alternator failed all their tests. FWIW, I didn't get the complete warm & fuzzies that either place knew exactly what they were doing with this older piece of gear. It was manufactured before they were born. (Yeah, that's a bit of a cheapshot. )

Do I spend the time and money buying a rebuild kit and trying to rebuild it? Or just get a replacement with a limited lifetime warranty?
Here's where my thinking is thus far...(in no particular order?)

• The alternator had the diode trio replaced maybe 15+ years ago?
• My time is money. While I'm likely capable or performing a rebuild, I've never done it. I could spend an hour just trying to decide which place to get it from. Then the rest of the day watching YouTube videos that walk me through replacing the parts.
• The rebuild kit (say $40'ish?) + my time (at least 2 hours when I'm realistic about it) --vs-- just buying a plug & play replacement? Advance Auto has the AC Delco for like $75. A different brand reman for like $65. I'm not even certain that a rebuild kit will resolve whatever problem I have.
  • I guess that same logic applies to replacing the entire alternator...there may still be an underlying issue such as some bad wiring.
• I'm leaning towards purchasing the AC Delco unit so I can just drop it in and hopefully be back in business.

So what does the peanut gallery say? If you're on the "just buy a new one" train, any recommendations on brand and/or place to buy it?

 

[bill81vette]

Hey!Andre how have you been? I have rebuilt mine.Eg,new brushes and diode trio.I used toothpicks to hold the brushes back uncheaper and til I reassembled the case.I thought it was much less expensive than a reman,plus its the alt.that it was built with.not to mention the satisfaction of doing it my self!

 

[gmjunkie]

Hey Evo,Shit Happens when your having fun! LoL! I think a man of your caliber can rebuild it standing on your head! Be sure to check the bigger diodes too and windings while you have it apart besides changing the trio ,Sometimes one of them can be the problem and slipping AC voltage to other components and make them over heat. The bigger ones shorted will definitely turn the light on Bright with the key off.

 

[Tom Bryant]

Hi Andre,
With your positive cable connected first and tightened I can't imagine that the amount of arcing from the ground terminal while connecting would cause any problem. A certain amount of sparks is part of the game with those side terminals. If you decide to disassemble I can run you through the testing of the individual components if you don't have a manual.

Tom

 

[Evolution1980]

OK, Y'all convinced me to give the rebuild a shot!
Suggestions on where to buy the rebuild kit? (A direct link to what I need would be nice!)

 

[Tom Bryant]

I'd disassemble and check the components separately so as to not waste money buying what you don't need.

 

[Evolution1980]

I'd disassemble and check the components separately so as to not waste money buying what you don't need.

At this point, my time is more valuable than what I'd spend testing individual pieces. As I understand it, the rebuild kits come with "everything", so I'll replace "everything". I'm not going to tear into it to replace only the diode trio and not the brushes or whatever else is in the kit.
Unless I'm not understanding your comment.

Any recommendations on where to acquire the rebuild kits? I.e., "Where would you buy a rebuild kit for yourself?"
Anything in particular I need to know to ensure I get the proper kit?

 

[Tom Bryant]

I'm just cheap. Back when repairing these was common in the dealer shop, rectifier bridges and diode trios were the common things to die with the rectifier making the most smoke. We almost always replaced the brush and holder assembly too unless they looked new. I'd do the front and rear bearings just because it's apart and if the brush surface on the rotor is good I'd test it and reuse if tests good. Same for the stator. If either of those is fried it should be pretty obvious when it's apart.

Tom

 

[Evolution1980]

This is the only rebuild kit I've been able to find online, and it's not available for two weeks.

Anyone have other references where I can buy the rebuild kit?
Otherwise, I'll just pop for a whole new unit. Example

 

[Tom Bryant]

That's a good price for a rebuilt and It's AC/Delco. Only giving $7.00 back for a core charge so I'd keep the original. Get the kit and rebuild it at your leisure for a backup.

 

[Bob Chadwick]

437 for a rebuild kit plus time and effort versus $45 for one already rebuilt. Seems like a no brainer to me.

 

[Evolution1980]

$37 for a rebuild kit plus time and effort versus $45 for one already rebuilt. Seems like a no brainer to me.

Yeah. Since Summit Racing is only 30 minutes from me, I just went up there today and picked up the reman.
Even though it was a 10si (I guess that's a form-factor designation?), it was pretty much a direct swap.
The bolts were a little smaller with this unit and the wings(?) for mounting it were a bit shorter. But nothing that a little adjustment of my mounting arms couldn't account for. And the plug was on more on top instead of on the bottom. Fortunately, there was just enough wire for it to reach.

And now we be back in bidness!!! I actually plan on driving it this year! Gonna be putting the 'driving' insurance back on it tomorrow.

 

[SS327]

You can change the clocking if the wires being short is a problem.

 

[Evolution1980]

So why not follow up on my own thread???
Up above, I said,

Hey everyone...
While attempting to reconnect my battery, I think I fried my alternator's electronics. I was having a difficult time getting those damn side-terminals to connect and I was arcing pretty good.

So, yeah, same thing this year. Annnnd I think I fried a component in the alternator again.
This time, my battery light and choke light comes on, and gets brighter as the RPMs go up. And I get the faintest lil' buzzy-chirping sound from behind the gauge cluster.
I checked voltage and everything is fine. Car starts, runs, charges...all OK, except for the choke light and battery light.

For the time being... I can start the car by leaving everything connected. Then I can simply unplug the 2-wire connector going into the alternator (starter circuit). And again, everything runs fine. "So janky!!!"

Questions!
1) I'm presuming the issue is related to that male plug. Looks like there's circuitry connected to that plug. Is that a standalone part that I can replace? Is that effectively the diode trio? ($6.69 @ Summit Racing)
2) Besides the overall Bubba nature of unplugging that connector after the car is started, am I going to hurt anything else by doing that? (Embarrassing that I'm even considering this as an option!!! )
3) SS327 above mentioned about "clocking the alternator" for wiring considerations. Does that mean splitting the halves and rotating the back section 90° or 180° ? (Just looking at the picture, I'm not certain that rotating it would solve the issue, as it looks like it might resolve it for one set of wires, but just make it more difficult for others. Possibly 90° counterclockwise might be workable, if that's what's being proposed.
4) Back to the battery... Has anyone converted from these annoying side-plugs to the more traditional(?) clamp style? Everything is so damn tight in the battery box, that I can't seem to reconnect without notable arcing every time.
5) As most of you would expect and probably do(?), I remove my battery each season and keep it on my workbench connected to a battery tender. I was always under the impression that you shouldn't leave the battery in the car and connected to the tender; Take it out for safety reasons. As I get older and more lazy(?), if I don't covert to side-post connections, what's the real risk if I leave the battery connected and the tender hooked up to it over the winter? I really truly despise those side connectors the older I get.

 

[Tom Bryant]

The 2-pronged plug on the top that is unplugged in your photo is the regulator. Easy to replace but can't be bench tested without using a regulator tester. The diode trio mounts to the rectifier (heat sink) on 3 studs to the bottom and one connector that goes up to a stud on the regulator. It can be bench tested. The rectifier is also called a bridge in some manuals. To test the diode connect one lead of the ohmmeter to the long diode connector and the other to one of the 3 short connectors. take a reading then reverse the connections. Do that with all 3 of the short connectors and the long connector. You should get a high reading connected one way and a low reading the other. If not, then the diode is bad.

To test the rectifier bridge, connect the ohmmeter from the grounded heat sink to the flat metal on one of the terminals. Test it on all 3 terminals. Reverse connection and test them again. If it reads the same both ways replace the rectifier. To reassemble the rear housing back on clean the brushes and push them back into the holder against the spring. Insert a wire or long toothpick through the holes in the holder to hold the brushes retracted. Once the housings are reassembled remove the wire allowing the brushes to snap against the stator. If you need new brushes order the brush holder assembly. it comes assembled with the brushes and a brush retainer pin already installed. There is also a capacitor in there, but I think it is just for radio noise suppression. I don't ever recall replacing one of those. The rear bearing is easy to replace if needed but the front one requires a puller.

I don't know if you can clock your housing without some wires being too short. I don't think it will hurt to run it unplugged. It just won't work. I got a side terminal wrench from the good folks at Harbor Freight for a little bit of nothing that makes it easy to remove the battery cables. It is a rachet and allows plenty of room to work. You shouldn't have any arcing if everything is off, and you disconnect the ground first and install the ground last. Clock and radio memory will still be drawing a minor amount and might make a small spark but not any arcing.

Tom

 

[Evolution1980]

Thanks, Tom! I'll give it a shot.

So here's an update.
In my recent post above, I forgot to mention that when I parked the car and ignition was off, the accessories were still running, as in, blower and everything were still active. When I unplugged that regulator wire, everything shut down. So I figured, "OK, I better leave the unplugged until I'm ready to resolve the issue."

Fast forward to just now...
I decided to go out and plug in that connector and see if the accessories still turn on. They didn't. My first thought, "Oh, good!". And then I paused and decided to check voltage at my brand new battery. ... DEAD! As in reading just over 5v.

So hopefully, that battery isn't damaged from what is essentially a full discharge.
I went and disconnected everything from the alternator's positive terminatl and left the plug disconnected.
I just put my battery tender on the battery to slowly bring it back to life...hopefully.

So what's the diagnosis on the alternator / overall situation? With the ignition off, something completely discharged the battery.

 

[Tom Bryant]

That sounds more like an ignition switch problem. With the ignition switch off you should only have power to the stop lamps, hazard lights, radio memory, lighter and clock. Power will also be available to the interior lights when you open the door, headlights if you turn them on with the light switch and alarm if turned on.

Blower motor, wipers, power windows, backup lamps, cruise control, gages, dash warning lights and defogger switch and maybe something else I can't think of, should only have power with the ignition switch in the on position. I suggest that you disconnect the ground to charge the battery and when the battery is charged, connect the ground cable and the alternator plug and check these things I listed to see what is on with the switch off. Watch the gages when you touch the ground cable to the battery to see if the needles swing and listen for the blower motor. If these and other things come on with the switch off, you have found your battery drain. Try cycling the switch and wiggling it to see if it will go off.

By unplugging the alternator, you are interrupting power to the harness to the ignition switch and fuse box for "hot at all times" accessories like the hazard lights, which is why things turn off. With the switch off, the only way power can get through the ignition switch to the fuse box "hot in on" items like the blower motor ect., is for the switch to remain in "on" when it's turned to "off". There is always power to the ignition switch, but power can only go through the switch when it is either in the "on" or "accessories" position.

To further confirm the ignition switch is the problem, disconnect the battery ground and unplug the harness from the ignition switch. Confirm that the switch is in the off position. Using your ohmmeter check continuity across the switch from the "Bat 3" terminal that had a red wire on it to the "Ign 3" terminal that had an orange wire on it. I'm assuming that 1980 wire colors are the same as 81. If not and the switch isn't marked, I can post a diagram of the switch terminals. Anyway, this is the "hot when on" circuit and there should be no continuity with the switch in the off position. If there is, bad switch.

Oh, and about the clocking. Our 81 is clocked 90 degrees from yours so the 2-prong plug is pointed at the fender well. It is the original alternator, and the wires seem happy there.

Tom

 

[Evolution1980]

Tom, so I wasn't quite reading between the lines in your final paragraph about checking things on "Bat 3" terminal and "Ign 3" terminal. That notwithstanding, I went ahead put in a brand new battery and recorded some results of various scenarios.

Table of "Did it turn on?"
w plug and w/o plug refer to the two wire plug going into the alternator

	HORN​	HEATER​	RADIO​	HAZARDS​	WINDOWS​	TURN SIG​	BATT LIGHT​
IGN OFF w/o plug​	​	​ ​	​ ​	​	​ ​	​ ​	​ ​
ACC ON w/o plug​	​	​ ​	​ ​	​	​ ​	​ ​	​ ​
IGN ON w/o plug​	​	​	​	​	​	​	​
IGN OFF w/plug​	​	​ ​	​ ​	​	​ ​	​ ​	​
ACC ON w/plug​	​	​ ​	​ ​	​	​ ​	​ ​	​
IGN ON w/plug​	​	​	​	​	​	​	​ ​
IGN OFF w/plug​	​	​	​ ​	​	​ ​	​ ​	​ ​

On of the interesting things about this table is the last row.
With the plug remaining in, if I had the heater going when I turn off the car ("IGN OFF"), the heater was still blowing until I switched it off. Then it would remain off. Strangely, this behavior seems to be inconsistent.
As well, now when I look at the battery light with the IGN OFF and the plug connected, the battery light barely visible. Like, I had to make sure I was actually seeing it by turning all the lights off in the garage. But it definitely goes out when I unplug that plug from the alternator.
With the connector unplugged, I checked voltage across the male pins and it's reading just over 9v. Is there always supposed to be voltage across that connector?

 

[Evolution1980]

More updates...
Since I had some time today, I replace the battery for a new one and I took the alternator off and opened it up to bench test.

Using my ohmmeter, I first tested rectifier bridge.
My testing instructions said to...
Start with the (A) Grounded Heatsink.

• One of my leads on the fin, and then other checking from points (1), (2), and (3). Ensure the voltage is the same for this set.
• Switch the leads. Ensure the voltages are the same for this set.
• Between Set 1 and Set 2, one set of voltage sets should be higher than the other. "CHECK!"

Now check the (B) Insulated Heatsink and perform the same test sets.

• In this test, both sets had the same voltages; There was no higher/lower testing across the six testing points. According to my instructions, there should also be a high/low set on this test.

I then performed a similar test on the (C) Diode Trio. This test appears to have passed. "CHECK!"

My instructions also noted that some models may have a (D) Resistor. However, it didn't say anything about testing it. But I did and it shows 0.1 ohms.

I didn't fully understand the directions for bench testing the (E) Voltage Regulator, but the directions for doing that while installed and the car running seems fairly straightforward. I have not yet reinstalled the alternator because I'm waiting to hear back from y'all if there's a problem with the rectifier bridge (B).

I did start to look under the steering column into that rat's nest of wires. The only thing I'm 100% certain of right now is that I don't have the same ability nor tolerance that I had 20+ years ago when I would contort myself to get under there. I just don't bend that way anymore!

Oh yeah, there was something else I wanted to mention. My mechanic told me that behind the center console cluster, there is a resistor or something on the small circuit board or circuit tape back there, and that can go bad causing my battery light to illuminate. It's been 20+ years since I've pulled that out and tinkered. I don't really recall what's back there, other than the circuit tape and lights. Anyways, could "that" be the real root cause? Or just a red herring? Or a downstream failure caused by the alternator?

ANOTHER UDPATE:
I just got done looking around for a rectifier bridge, and while I was at it, a voltage regulator. Those are half the total cost of the alternator itself. Similar to when I started this post 2 years ago, it doesn't seem worthwhile. And, I didn't even see the same rectifier bridge that I currently have. So it might be a non-starter anyways.
I did look up a diode trio. People on eBay have 'em. Seem to average about $12.
Again, do I chase parts or just go get a new alternator? I don't even know for certain if that's my problem. It might be my ignition switch as Tom mentioned above. So for now, I'm in a holding pattern until I get more info from you veterans!

 

[Tom Bryant]

I have been looking at your chart and thinking about this. Your heater blower should not run unless the ignition is on. It should come on with the ignition on as part of the ventilation system. You don't have the option to turn it off completely. The battery light should come on full bright when you turn the key on but go out when the engine starts, unless the alternator isn't charging. Heater blower on my 81 does not run in ACC. I don't think yours should either. I'm thinking there is feedback through the alternator. Your test of the insulated sink showing the same readings both ways seems to indicate that the rectifier is bad according to the GM manual. I found a simpler test in the Haynes manual that seems to confirm this. It says that if the Battery lamp is on with the switch off, disconnect the alternator plug. If the lamp goes out the rectifier is bad. This would also show where your drain is coming from. Not sure about the voltage across terminal at 9v. I'll check that on mine tomorrow.