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TR2/3/3A TR3A alternator is installed and working

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PeterK

PeterK

Yoda
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Busy weekend.

Got the GM 7127-3 alternator installed in the 3A today. After removing the generator, I pulled the old bracket to drill the rear hole to 3/8". I used 2 - 3/8-24 bolts and a grade 5 coupler with jam nuts to span the generator bracket. Some said to get a 7" bolt and I would have used this with a spacer, if I could find one without mail ordering the thing. Funny, but nobody locally sells longer the 6" and then not grade 5 or 8. Also if you use a long bolt, you must install it in the bracket before you install the bracket or the exhaust pipe will be in the way. Using the original adjusting bracket required a 1/2" spacer on the waterpump mount to get the pulley aligned properly without having to flatten the adjusting bracket for pulley alignment.

I gutted an old regulator to use the external terminals and preserve some degree of originality. The cover was in 3 pieces but after JBWelding, sanding and Krylon fusion, it looks very nice. Can't say "new" because the cover is bakelite which is a dark brown, semi-flat finish and now is black gloss. But still nice looking.

Wiring was kind of a pain because I had to extrapolate what I needed to do from the information that I gleaned from the web. Once I figured out what DMI was trying to do, it was easy to wire. His instructions are a good cookbook but I prefer to know what I'm doing before I attempt it. After installation, my idiot light works as before, ammeter works. I wired a direct feed from the post on the alternator to +side of the starter solenoid (also newly replaced). This sends the power directly to the battery instead of though the dash. I found it interesting that at 500rpm idle (just redid the jets and floats earlier this week so my idle is nice and smooth this low!), the dash light was on until I blip the throtte and the exciter kicks the alternator in. I think this is a SI alternator for low rpm kick in but I guess not 500rpm.

The hockey tape was a good tip for wiring harness cover too. Thanks to whoever posted this.
 
PeterK-

Great work! I know this has been covered on the net here and there, but any more details you can provide will be greatly appreciated - I will likely go over to an alternator on my TR4 when the generator misbehaves, but I have yet to see a 100% clear cut path on how to do it. So here's some extra questions while you are still glowing with your successful work:

1) What are the modifications to stock - sounds like just minor change to original bracket, and refit of regulator, which is a cosmetic option . Any grinding anywhere?

2) Why the 7127-3? Is this just to give the third wire/idiot light functionality? I'd definitely like to retain that feature as well.

3) By going direct charge back to the battery, does your ammeter behave well? No need to shunt or swap out to a voltmeter?

4) What did you use for pulley arrangement? If you have a different fan belt, what's the model?

Any pics? How about driving down here so I can look it over myself and take some notes? Now see what you started!

Randy
 
A.
1) Per others instructions, I needed to cut 1/2" off the rear mounting boss on the alternator. There's already a protrusion there and cutting it off allowed the pulleys to line up. Easy cut on a bandsaw or by hand.

2) The 3 wire setup allows the idiot light to work. The "-3" on the model denotes a 3'oclock position on the back for the connections when mounted. That puts the connection outboard towards the fender.

3) A voltmeter will be installed next to show actual charge. The ammeter seems to behave normally in testing so far.

3) I switched out the narrow alt. pulley for a 3/4" wide one that is commonly sold for tractor conversions. Cost $12.60 on ebay, available from alternator repair places. I did not convert to narrow pulleys on the TR.

4) The belt is a Gates green stripe, NAPA 25-24379 purchase from CarQuest. Put the belt on before bolting to the bracket.

In this case, a picture won't show much, just an alternator instead of generator. Using the dummy regulator keeps a non-molested look too. I had to solder acopper wire inside the regulator to connect A1 and A terminals together.
 
Thanks, very good information. It sounds like your bolt arrangement is a better option than the 7" long bolt if you have to get the belt on before you bolt it on.

With the alternator, is there a socket plug available to tie into, or did you just tie wires to each terminal separately?

Randy
 
For the plug, any parts store will carry the plug for GM alternators. It has two wires attached, usually red+black or white+black. The black wire feeds the idiot light through terminal D wire on the old regulator box, and the red/white gets attached to the post on the back of the alternator with the big wire (use 10 ga or 8 ga) that you direct run to the + side of the starter solenoid..
 
You might also consider what Dan Masters has to say about using the ammeter with a higher output alternator in this pdf from his website. See page four. The most logical modification seems to be the shunt for the ammeter. That will reduce the amperage going through it by approximately half. Of course, the reading will be half, but you won't toast the ammeter that way.
 
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