How to rebuild a 10SI alternator

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[@dgc940]

I was rebuilding these back when I was just a kid back in the day. Back then could go to the chevy dealership and get genuine parts for them and in stock. used to chuck the rotor in drill press and clean brush contacts with a fine file then buff with very fine grit paper. Then be cruising the drag by evening. Same with starters I was poor boy. Back then our little town also had 2 auto electric shops Thats the good ole days.

[@rebuilderinabox]

Yep and they knew it, too. The very next designs were specifically intended to be non- rebuildable, they even published TSB's touting the CS series was not rebuildable. (which was $ driven propaganda) After market rebuilders were furious and I was one of them. Then GM ditched Delco Remy for foreign cheaper labor. Sorry Delco, don't try turning to the aftermarket you just got done trying to screw over!! What goes around comes around.

[@user-ev4hn8mq9p]

Happy to have found this information,keep it up

[@dpete8995]

Outstanding demo, thanks!

[@JamesNewsomeCaiLeighAnna]

Outstanding tutorial on disassembling, reassembling, and replacing worn parts in an alternator. I don't know that I'll ever try this, but it sure helps me better understand the mystery of what's inside an alternator.

[@johnsweeney1400]

Thank you Mike. The best video "quality and informative" that I found for the help I needed. Was changing a regulator and went back a week later to reinstall, and no one else shows the insulating washers on the brush holder so I put the flat washers between the brush holder and new regulator. Obviously over-isolated the bushes. (My common sense was to over cautious.) Thanks again!

[@512bb]

Mike, you are a very good teacher & I have no doubt very good at the service that you offer.

[@rnewtonsgarage5926]

Great video simple and to the point.

[@mikeanderson1139]

just finished my 100amp upgrade.....thank you thank you thank you.

[@chrislovallo9335]

Excellent video, good quality, good info, no unnecessary b.s., clear instructions.

[@rebuilderinabox]

Thank you for the kind words

[@demoking1422]

Great video very thorough the tips you give during the process are very helpful Thanks !

[@madclassics]

Thank you one KZbin video that I actually learned from

[@michaelisicoff8917]

Great video thanks from 1969 GTO

[@antegas]

Thank you very much! Mike. I enjoy your vid a lot. God bles!

[@VWC318]

Very informative video! How do you remove old bearings?

[@jimwhite5964]

Thanks for a great video!

[@lucnadon1067]

job well done very well explained...

[@patrickbetscher4990]

Needed that tip on the brushes and the springs. thanks!

[@ssd3602]

What happen with the springs

[@gogglespaisano6483]

Watched many vids to find that tip. This is the only one that helped. 👍🏽✅

[@bigg8539]

Thanks for making this video...I found my dads old alternator that was in his 64 chevy impala but he had replaced it and put it somewhere for,I don't know how old but I'm cleaning it up and I needed some tips so if u got Facebook just comment on one of my KZbin video bc for some reason I have to approve comments but u can give my your Facebook and if I have any questions I can pm u on Facebook again thanks for this video really appreciate it I'm only 15 yd and I'm still learning how to build cars I'm still working on a 52 gmc pickup with my dad and a 67 chevy impala SS then one day I'll be working on a 67 C10 pickup

[@Garagemonkey11575]

Thank you your info save me about 40 bucks

[@tomrusso7360]

Love the paper clip tip...I would probably use a drill bit not having much succes in bending a paper clip that straight. Otherwise, great detail for those with mechanical aptitude but never having taken on an alternator rebuild. I've farmed them out paying $250.00 plus shipping and was disappointed when the rebuilder blasted the hell out of the aluminum codes that they came back distorted. Minor but an incentive to DIY! Great job and thanks.

[@guineapigzed]

I’ve recently used a toothpick

[@ercost60]

GREAT video! Thank you for posting! Too bad your website does not list a kit for my '67 Chevy Corvair.

[@orquestabrava]

Hi Mike. I like your video is very detailed. I have a question. My 1975 Firebird sat for 20 years and now I'm in the process to bring it back to life. I'm done rebuilding the engine and wasn't sure if I should do anything to the alternator. It was working fine then 20 - years ago, I;m just concerned that it may need some type of lube detail to it or something after sitting? Or should I just clean the outside and plug it the way it is. Is there an easy way to lubricate the alternator with out going through the disassembly? Your take is much appreciated bud!

[@gulabkeerio1930]

good job

[@griffmillerii1885]

Good video. I love the serviceability of the 10SI and 12SI alternators. It's probably not super-critical, but I'm pretty sure you're supposed to drive the rear bearing in until it's flush with the housing, as viewed from the exterior. I've never had a problem with the shaft touching the back of the bearing when it is installed in this manner.

[@rebuilderinabox]

Years ago, when they came from the factory, the needle bearings were flat with the back plate. However, for most modern day brands readily available on todays market we recommend a 1 mm external offset.

[@griffmillerii1885]

Mike Lauer so if I have an honest-to-goodness Delco Remy casting, flush is good, otherwise check clearance?

[@rebuilderinabox]

@@griffmillerii1885 Flush is always asking for trouble. We build and sell 5-6 per week since 1985. Also, we sell kits with a warranty, so we don't want our customers to be confused.

[@abousamah1967]

Very nice description Thanks very mutch Can you show me internal wiring of such alternator

[@williamquispe7462]

mike have problems with Delco remy 36si brushless alternators and not as operation and diagnosis. greetings.

[@stringfellowhawk3392]

excellent video. Vey informative. You did a nice job. Thanks!!

[@bazrazin1]

whats the construction of a alternator rotor, a two wheeler has a circular magnetic disk rotating over stator coils.

[@INTERNA9]

THANX

[@Tom-wq2mz]

Very well explained. Nice work. What can you tell me about the 12SI. Did Pontiac use them in 1975. I was told my alternator was a 10SI but the far right is just like mine you state it's a 12SI. Ear at 12 o'clock two wire terminals at 9 o'clock from the rear or 3 o'clock from front view & Battery post below. What's your opinion. Thank you

[@rebuilderinabox]

12SI and 10SI are very similar in construction, just different parts. Pontiac didn't have 12SI in 1975. You can send us pics thru [e-mail] and we will let you know which one you have. Show close up pics of stator windings and we can make an educated guess at amps output. Time positions don't matter or provide ID info. Also we can provide app recommendations based on your needs. (originality or performance)

[@dougbeckwith768]

Curious about the meter on the right reading in amps . Did you have a clamp on DC amp meter for the fluke that read out in a mV signal and a multiplier?

[@rebuilderinabox]

The Hall effect has to be zero ed in all the time, and it's a pain. With a shunt, you set it up once and forget about it. I think it's more accurate, too.

[@gravelman5789]

i bought a rebuilt Napa 12si, 105 amp alternator, it has a resistor from the grounded brush holder, to the trio??? it has never worked do you think it will work if i remove it? its a normal installation so pretty painless, to test....😁

[@rebuilderinabox]

Removing that won't make it charge.

[@johnhodg8400]

is it possible to remove the two bearings and put new in and how?

[@rebuilderinabox]

Yes, we show you how to replace bearings among other important components.

[@eldaminoTA]

Hi - this is a great video, very detailed, thanks for taking the time. I think you may have identified the problem I'm seeing with my 7135/27SI alternator on my 74 Trans Am. I hope so anyway. I am seeing erratic voltage output from the battery post when the car is running. Skips around anywhere from 0 to 14, 3, 6, whatever. I tested everything on the charging circuit from battery to wires to grounds, all is good. I had a local shop check the alternator, they put a new regulator in, said the rest was in perfect shape (it's got very low miles on it, even though it's from 1998, less than 2k). I put it back on, same thing. I noticed the battery post is moving around (can rotate pretty freely, once nut holding wires on is tight). Based on what you noted about that post needing to be tight (internally) I am thinking that might be the issue? Possibly arcing as you mentioned, or simply not making good contact. And if so, I feel, after seeing your video, I can take the back off and tighten it down, although the brush retainment seems a bit tricky. The shop said they got 14.5 out of it on bench testing. Before I take it apart, am going to run it with no wires on the battery post and check output.

[@rebuilderinabox]

Yes the post must be tight. But readings at the alternator output would never drop below 12.6 with a fully charged battery. Readings at the alternator of 0 or less than 12.6VDC indicate a faulty hot wire or fuse link. (if you're sure the grounds are good).

[@eldaminoTA]

The car is a street/strip car I had put together in the early 2000's by a shop that built sandrails and off-road racers and ran superbly until just about a month ago. I was in a car accident before that and could not do the work myself at the time. The issue I'm tracking down, is the engine (stroked 455 Pontiac, high compression race engine) won't idle in drive or park any longer, wants to shut off. Runs great off-idle and in park (it idles at 1400 RPM). I rebuilt the carb and fuel regulator last year after not driving it much during the pandemic, ran well since, this feels like an electrical issue. Tested everything including taking the 3 year old rear-mounted battery, on a tender with kill switch set to off when not driven, to a shop where it tested good, checked wire continuity on cables (and cleaned all fittings), MSD system including box and coil and dist., put new spark plugs in, checked fuse panel, grounds (2 heavy-duty to engine alone) accessory wiring for vacuum pump and electric fans, etc. And finally found the varying current at alt. New reg put in it, no difference. I was planning to run the car with the 3 wires coming off the alt clamped together and removed, to see if it puts out 14 v that way. Then go through the 3 (one directly to battery via the kill switch, one to new accessory wires for fans etc, the other I'm not sure where it goes yet, figuring to fuse panel but all 3 have been there untouched since 2005) to see if one of them is the issue. When I took the alt out I found the #1 wire on the plastic plug was broken internally, replaced the plug, soldered wires on, verified 2 gets battery signal. This has been driving me nuts, as it coincided with my wanting to sell it and started the day I was bringing it to the person doing so. So I'm looking at anything at this point, which led me to your video due to the loose bat terminal on the back. I appreciate your reply, I will try to find a way to test for that.

[@eldaminoTA]

​@@rebuilderinabox Quick update on this frustrating problem. I was able to turn the bat post on the back of the alternator with a 1/2" wrench till it was solidly tight. Reattached the wires, tested it, same erratic voltage. Removed the wires so nothing attached to the alternator except the side plug (for terminals 1,2), clamped the other 3 wires together and started it. Checked the voltage coming off the bat post, same 0, 6, 14, 3, 0, 13, etc etc. It really seems like something is shot in the alternator, unless it's possible the feed from the battery into #2, (#2 has battery voltage applied if the battery kill switch is set to on, as does the alt bat post, whether the key is in or not, and #1 only shows voltage when car is running) or the output from 1, to the dash light, could be screwing it up? I was debating about removing just terminal 1 and trying it, but am unsure if that could cause an issue. Biggest problem with a new one is this is a 150 Amp alt. And it's hard enough finding the correct case style, been impossible to find one with more than 100 amps. Maybe it will be OK with that, but not sure, has high-draw electrical accessories, fans, vacuum pump, elec. fuel pump etc.

[@rebuilderinabox]

@@eldaminoTA If the battery is in the trunk, there should be one continuous ground cable to the block. Don't use the frame or the chassis as a ground path. Get some #10 gauge wire, Feed the alternator post from the starter solenoid post, bypassing kill switch as a test.

[@eldaminoTA]

@@rebuilderinabox Thanks for the information - the ground cable, in the trunk, goes to a welded bracket the shop added to hold the fuel cell. That is welded to the body by about 2" of weld. The bolt it tightens against (welded to underside of bracket) is unpainted. In the engine compartment they ran heavy ground cables (2) to the engine, one from the body, one from the subframe, and another connecting both. There's also various grounds from the body to the fans, and vacuum pump harnesses. This problem with it wanting to shut off while warmed up in drive or reverse started roughly 3 weeks ago now, after 19 years. In the past any issues with the engine at low speed were due to the MSD billet dist., buildup on the terminals in the cap and at the reluctor ends (light surface rust) creating an irregular spark, or buildup on the spark plugs. So the first thing I did was clean the dist with scotch brite pads as usual and blow it out with air. And put new plugs in, although the old ones were in good shape. When that didn't help I started checking everything else. This morning, after more research I tested the alternator's #1 terminal's function, as I was not seeing a light on the dash when putting the key in run, I could not remember if I wired one in when I built the custom dash, or if it ever turned on. Thankfully I shot a video of myself starting it, many years ago, showing the dash, I noticed no light came on. But just in case, I wired a 12v standard type dash light in-between a switched 12V+ source and the #1 terminal on the alternator, when the key was on, light came on, when started, light went off, however it is still doing the erratic voltage output. I don't think the ignition switch could be involved, as the car starts, runs (except in drive) and shuts off fine with it. I think I have a source for a 100 amp 7135 style alt and am going to order it, swap it and see what the output is. If it's still jumping around, then I have no more ideas on what to search!

[@elvinkasumovic3296]

How change starting charge rpm on alternators ? My car runs slowly then normal I see some tractors have capacitors out side the case my car runs around 300 500rpm on porpuse so I wuld like to ceap it but alternator is bitcchy .culd I use the the R terminal on my starter selenoid to exite the rotor? To give my litel bost on start up?

[@rebuilderinabox]

No. Use something on/off with the ignition switch (not the coil). Check fuse box. F terminal or #2 is hot all the time. #1 or R is on/off with key.

[@koelzspeedgarage2796]

Hi Mike, I have a one wire alternator on my street rod that has a 350 chevy motor.I bought it at NAPA. I don't know what Model it is or remember many amp it is. How can I figure out what it is. I don't think it puts out enough amps when I am running my AC blower and my radiator cooling fan. Plus my MSD distributor, etc. Especially at idle. How do I figure out what I have, and , is there a way to boost its amperage output? install a bigger stator winding and stator maybe? Please help.

[@rebuilderinabox]

Well the thing is, we already helped as much as possible with the video. We don't sell any 10 SI parts because E bay is flooded with thousands of 10SI parts. Just buy the parts off a responsible E Bay-er or better yet directly off the web. The regulator is what makes it a self exciter (one wire) and the stator makes it a higher amp. Don't get crazy with a lot of amps, it's not very compatable with self exciter unless professionally assembled. Try to buy a moderately priced kit, some of that super cheap stuff is a waste of time.

[@koelzspeedgarage2796]

@@rebuilderinabox Thank you Mike for your time and expert advice. Great Videos.

[@edwardojr2838]

Do we need the noise suppressor?

[@rebuilderinabox]

No, but it could help the voltage regulator last longer.

[@JacobAHull-nx6rx]

How you remove the rotor shaft?

[@rebuilderinabox]

I've not done that in many years. A shop I used to work at did, I think it was a 50 ton press.

[@johnhodg8400]

all i need are the bearing replaced , its making noise.!!

[@guineapigzed]

Isn’t it called a diode triode. Three diodes?

[@rebuilderinabox]

Back when we did hundreds a day, we called them trios for short.

[@abousamah1967]

Where is the eesistor between regulator terminals Or its not nessesory What its function

[@rebuilderinabox]

We stopped using it in later years. It would put the idiot light on if the rotor circuit fails.

[@abousamah1967]

@@rebuilderinabox Thank you very mutch You make good jop nice explnation Thanks

[@pkerit308]

17:35 I came here to learn how to test the rectifier

[@rebuilderinabox]

The cost and ease of installation during service, verses doing the job twice, makes the rectifier a routine replacement. So we may not show you how to test it. The rotor can be tested at any point during the rebuild, but you will almost never find one shorted to ground. We have occasionally found open (no continuity from copper ring to ring) ones though.

[@jdvnautic]

Getting the nut off seems easier than it is. I just can't get it off my pulley. 😒

[@rebuilderinabox]

1/2 inch impact. They should be easy. Maybe yours needs heat or rust bust.

[@jdvnautic]

@@rebuilderinabox It's a new alternator. I'll will try to get it loose with heat. thanks