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Alternator/Headlight Upgrade

114114 Views 503 Replies 89 Participants Last post by  kwilford
Early in this thread you mentioned about upgrading the alternator using GM stuff as follows:

Well, since Bob brought up alternators....
I just borrowed a friends digital camera and I am taking some pictures of a simple way I use to back-fit Opel motors with a 60, 85, or even 140 amp GM alternator. I've even got the wiring figured out so the charge light on the dash will still work. I'll get the picture and some detailed drawings posted when I get them worked out enough to be presentable and double-check the parts fit into a GT. (What works in my Kadett or Manta only sometimes fits into a GT.)

I'd be very intrested in you sharing any info that you have on this upgrade. I want to upgrade my GT alternator and from what I've found out the GM Delco 10si style alternator is a great way to go. Internal regulator, good output even at low idle speed, well designed and cheap too. How did you do it? I'm all ears.
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I followed the advice of this thread a bought a Delco 7127 63amp alternator. I also use the universal GM alternator bracket that looks like an "F". What I did differently than everyone else was the upper bracket. I used half of the stock bracket and half of the GM universal upper bracket for small block chevys. I cut 4 notches in the GM bracket and bent it into a smaller radius, it was shortened as well and then welded the the first half of the stock bracket. If I had it to do over again, and I might, I would cut more notches and bend the bracket even further so it would not rise up next to the distributor.


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Hi I am in the process of posting a new & better alt. choice using a GM
"CS" 105 amp alternator the case is smaller than the org. Opel alt.
( 135 mm dia. for Opel and 120 mm dia. for GM ) I have installed this with a
Chevy alt. bottom bracket and using the stock opel bracket . This is a one wire hookup and the charging light in the Opel is still used. The "CS" 105 alt.
is a better charging alt. at idle than the "SI" 63amp alt. and can respond to high amp. draws in traffic or poor weather I.E. wipers, coolant fan ,headlights, radio or etc. on at the same and at low speed . I have many photos to resize and do the write up to cover all questions and see if there is any interest.Hope this helps on your upgrades. Guyopel
Bummer:( , I would have done the better one. How much does the new one cost?
The one I installed was a rebuilt unit and parts ( bracket , alt.plug )
was about $100 to $120.Guyopel


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Have any of you tried the one wire alt from jc whitney it just has one wire to the battery used one in my 69 worked real well
alt info

well there are many alternators out there that use only one or two wires ur main battery wire and an exciter wire and the ground usally runs thru the main mounting bracket. theres a nice 80 amp one ive seen used to use on the 70's early 80's chevy trucks and then the current one they use know forget the amprage but they use it on the later 80's model chevys works pretty good and is the same size as the gm alt. i put on my gt, pretty easy to install as well, only had to modify the lower bushings, just look around and make sure u get one that has the right upper mounting locatin for your adjusting bracket.
From one of my maintenance manuals for the later GM products, late 80s and up, it says the alternators that have riveted case halves are lower than 100 amp ratings and the ones with bolts holding the case halves together are greater than 100 amps. But then if you get a reconditioned or rebuilt alternator, all bets are off. :confused:
A quick and dirty way to find out the amps is to check with your local auto parts store, there are usually 2-3 different alternators that will fit a car, so it should fair easy to look for the part/model number when you're out at the recyclers. HTH.
would anyone care to elaborate on the 'bypassing the amp guage' comments. i trully don't follow. i got hte 7127 ac delco alternator and the pigtail that goes with it. i'm going to go ahead and mount the monstrosity in the car, regardless. slightly nervous about damaging what i consider 'priceless' (snicker) equipment by totally foobaring it.

and correct me if i'm wrong here plz.

Large stud on back of alternator -> stud on starter where battery connects.

run a ground wire from back of alternator to block or whatever...

Red wire on pigtail loops back to the stud.

white wire gets spliced wit hthe blue white stock wire runnning to the amp guage light.

which reminds me. HOW hehe... does connecting the alt to the trouble lamp also 'excite' the alternator?
and why would having the amp guage included in teh circle cause an issue. i just couldn't make sense of that site. (isn't exactly car savvy)
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If I remember correctly it is the red wire that loops, as you describe it, that excites the fields within the alternator. The trouble light connection is just a bonus, you don't really need it to have the system work. It's been awhile since I read all the stuff you are reading, but I believe this to be correct. The thing about having the Amp gauge in the circuit is that when you kick up the amperage capability of the whole system and then don't fuse it, but run a relatively long wire through the dash, there is a possibility of overload and fire.
put a 30 amp inline fuse on the b+ wire? maybe?
First off, by all means put in a hi amp fuse, the original wiring has a fuseable link at the alternator output, also there is one on the red wire at the starter where the battery cable hooks up and powers the whole system. If you don't have a DESTEC schematic or access to a wiring diagram, here's how the original charging system is hooked up. Output from the alternator goes via the red wire to a stud on the fuse panel, through the buss bar and out the other stud via the Red/White wire to the B+ stud on the amp gage. From the L+ stud on the amp gage via the Red wire back to the fuse panel stud opposite the stud that came from the starter. That setup gives total amperage indication + or - of the entire electrical system, because all power into and out of the battery and alternator goes through the amp gage. On the original alternator/regulator there are three wires into and out of them both. The only other wire is the Blue/White wire from the amp gage lite. That lite has "switch on" power to one side of it and alternator signal power on the other, This difference in voltage between the two sources of power lighting the lite is what signals the alternator to put out voltage/amps. When the alternator puts out anything close to system voltage the lite dims and as voltage going out increases, the lite goes out. If you do not have the lite in the charging system you will not get any alternator to function, it is the difference in system voltage and alternator voltage that makes the alternator work. In order for the single wire alternator to work, you have to have the Blue/white wire go to the plug on the alternator. If you hook up the alternator output to the starter terminal where the battery hooks up, you will not have any indication of charging or discharging, because you take the ammeter out of the circuit. By looping the wire from the alternator plug to the output stud, the alternator will see no difference in voltage and will not generate any output to the battery. HTH.
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i'lm thumbing through the wires under the hood and i've realized something.

i have no blue/white stripe wire.


coming from the 'bundle' of wires going towards the regulator and coil and what not:

red - stud on back of alternator.
green - coil/distributor
clear - coil (oppoisite side of green)
black (no color) goes to same post as said clear wire.

red wire to 3 wire pigtail that connects the alt and regulator.

I assume, of course, that red is actually blue/white.

*shrugs* i'm being over cautious, normally, but with my gt, i can definately defend the point, seeing how parts are rare at best.
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maglinjosvinn said:
i'lm thumbing through the wires under the hood and i've realized something.

i have no blue/white stripe wire.


coming from the 'bundle' of wires going towards the regulator and coil and what not:

red - stud on back of alternator. Should have a fusable link and go to one of the 4 studs in the fuse panel
green - coil/distributor Should go the the tach
clear - coil (oppoisite side of green) Should go to fuse #5
black (no color) goes to same post as said clear wire. Should go to the starter solenoid vertical male terminal

red wire to 3 wire pigtail that connects the alt and regulator. That should be a fusable link and the Blue/White wire connects to it

I assume, of course, that red is actually blue/white.

*shrugs* i'm being over cautious, normally, but with my gt, i can definately defend the point, seeing how parts are rare at best.
Look for the Blue/White wire to come from the inside the vinyl covering of the instrument panel harness, it should have a male/female spade lug terminal connecting the two wires together. HTH.
ok. alternator is hanging off the spare engine. i took a random alternator arm out to my forge, bang bang bang, goes in, ground down the bracets, and away she goes. i gotta fille the groove in the adjustment arm towards the block cause the belt is WAY TOO TIGHT! lol. aside from that, golden

over all:

47 bucks. alternator and pigtail.

are two photos i've reworked. more to come. the first doesn't include the arm i fabed up, but i'll get a shot of it soon.
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right then.

doesn't work.

mechanically, its sound. nice and clean. the problem?

i dunno.

it WAS putting out a 17 volt signal to my voltimeter at the stud on the alternator

but that was the only place. fusible link? i think so. so i tested it at the fusebox. 0 volts. well shisa, thats not good. hows the car running? i dunno. so i go back out to the alternator, test the stud again and 12 volts. odd.

the little red dash light is on. continually. when i FIRST put the alternator in, the red light would come on till you started the car, then it would either go out or dim. now it won't go off.

... gah. i'm stuck. its pitch black outside and as much as i hate going to bed with a problem, i got no choice.
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You are really close to the solution. From what I have read (I think in this thread, but since I hit reply I can't go find it) there is one more wire to hook up. It is a white one (maybe?) that needs to go to the light on the ammetter that turns on the alternator. Without that draw of the light to kickstart it, nothing happens.

Search more here or for another similar thread on alternator wiring for the new single wire alternators. There is another plug that needs to be used.

I hope this helps.
See post nos.5 in this thread and post nos.40. for the wiring. If you purchased the alternator at a junkyard, there's a good chance it's bad. Take it to one of your local autoparts stores and get it checked. HTH, Jarrell
*nods* i bought the alternator brand new, but i am going to take it to be tested today.

the white wire IS connected. i'm going to be going under the dash to check all the connection points.

PROLY - going to have to take down the fuse block, clean EVERYTHING and put it all back to gether. go me. i'm considering replacing all the wiring going 'under the hood' from the fuseblock at this point in time, and adding my underhood GEO 91 storm fuseblock so i can bring the headlight fuse out front, the fuse for the alternator output, the fuse off the battery... everything. really handy peice of equipment.

I did i confess, lay a screw driver by accident accross something when i was ... what was i doing. lol. nice big spark. the alternator still put 17 volts out after that, and the idiot light did go out. *sigh*

i gotta go to work in 30 minutes, then back around 4 tonite, at which point i'll have a few hours. *has to be to work again at 5 am the next day. hopefully i can find a solution.
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well it worked. works. going on a road trip. i'll edit this post after work tomorrow to show you guys the solution.

in short. i bypassed the blue/white stripe wire. on the diagrams i saw for other cars w/ this alternator in em the white wire was supposed to be constant hot. period. the red wire. constant hot. period. so. i ran a relay from the key on fuses under the hood, and hooked a line up direct from teh battery so the alternator kenw the charge on teh battery. that point in time, the alternator either was putting out 0 or 63 amps of power. when i hooked it up that way, a nice 20 amps, which slowly went down to 0 or so as it charged.

thats it in a nutshell.

*lights are INCREDIBLE NOW!* lol. still putting cibie Zs in tho.
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