Alternator part # decoding

**Jeffrey S.** · January 26, 2004, 10:14 AM

Re: Alternator part # decoding

Theo:
On original GM alternators, the the dating is as you have said: first number is last digit of year, letter is month code, last numbers are day of the month. I have never seen any variation of this.
Jeff

**Terry M.** · January 26, 2004, 11:21 AM

Re: Alternator part # decoding

Theo,
Date codes can and do change format.
The 1980-1982 TIM&JG shows a date code system which is consistent with what you have posted. D059 is:
D = December
05 = date of the month
9 = year. Presumably 1979.
There are other configuration issues listed in the 1980-82 TIM&JG regarding where the code is stamped and so on. I suggest you purchase the manual. It will help you feel more comfortable in your future parts purchasers and may even save you some money.

**theo law** · January 26, 2004, 11:50 AM

Re: Alternator part # decoding

Terry
That's actually quite good news, although I suppose it makes things a bit more complicated! I was beginning to think it was a dodgy faked date code (although why someone would do that for an 80, I'm not sure!)

So does the D mean "december", and not April, being the fourth month?

I was actually planning to buy the TIM&JG very soon, will need to find out if it is easy to have shipped to my home in the UK...

In the mean time, assuming you have a copy of the 80-82 guide at hand, can I ask whether you think that date (1979) would be somewhat early for my jul 80 build vette?
I don't mean to get you trawling thru all the info for me, specially as i'm planning to buy the guide myself - it's just I may need a quick answer on the "correctness" of this part, quicker than it would take for me to order and recieve the manual!
Much appreciated, thanks!

**Terry M.** · January 26, 2004, 12:13 PM

Re: Alternator part # decoding

Theo,
Yes the D = December, NOT April. There are number codes for the first nine months of the year and then O, N and D for October, November and December.

The rule of thumb in NCRS is six months before the vehicle build for dated components. This is right at that line. What I can not tell you, since I have little experience in judging 1980 Corvettes, is what an alternator date might typically be. Some components on some Corvettes routinely exceed that six month window, and experienced judges know which components those are.

There are four different alternator numbers listed in the manual for 1980 production.

There should be no trouble, other than the cost, in sending the manual to England. NCRS has an active chapter there (if you are not in contact with them, do so. They are on the "contacts" page, see below). I am sure the sales office (more buttons at the top of the page) routinely sends parcels to Great Britain.

I suggest you send a message to the 1978-1982 Team Leader. I know he does not routinely monitor this board. He can be reached through a link on the page that comes up when you click on the button at the top of the page labeled "contacts." Be sure to tell him you are a member of NCRS, if you are. All of the team leaders are more likely to respond to a member's question. Ask him about the date situation.

**theo law** · January 26, 2004, 01:10 PM

Re: Alternator part # decoding

Thankyou Terry, for all the good info.
I've just now sent an email to the UK chapter for info about the judging guide, and will await a reply. It would definitely be a most useful book to have.
I will also get in touch with the 78-82 team leader, to see if he can shed any light on the subject. Any info I gather, I will post back here for everyone else to see.

I've seen the four different alternators listed for the 80, the correct one for mine is #1101075, for late production cars with rear defog. This is the number of the unit whose date code we are talking about here. It was also used for 81 and 82 cars, i believe.

As you say, the date of the unit in question is pushing the 6 month envelope - my car's VIN suggests a build date of July 3rd 1980. I'll be interested to see what the 78-82 guy has to say.

Thanks again for taking the time out to look those numbers up for me!
Theo

**Terry M.** · January 26, 2004, 04:28 PM

Re: Alternator part # decoding

Good, Theo. Sounds like you have done all you can for the moment. There might be some 1980 judges prowling the board here who can help out in the mean time.
You will likely have to purchase the TIM&JG from the NCRS sales office here in the USA, but your inquiry to your mates will not be for naught anyway. You should get together with them at some of their events for more encouragement. You will be able to learn much from them.
As of this morning our sales office was still shut down due to the Regional meet in Florida. The office staff that was to return by airplane may be delayed in the south due to weather up north. I expect those who are driving will be further delayed by the weather as well.
I misread the manual about the four 1980 alternator numbers, there are five. This was a new style alternator for 1980, and the usual production schedules may not apply. All the more reason to get the opinion of an experienced judge.

**theo law** · January 27, 2004, 06:02 AM

Re: Alternator part # decoding

Terry,
I had a very quick response from Brian Pearce, thanks for putting me onto him. He's gone away with some more of my car's information and I'm looking forward to a reply from him at some point today (tues).
Unfortunately, the UK chapter do not hold any manuals for sale, according to their chairman, who I emailed last night. Seems I will get a manual mailed over from the US.

You say there was a new style of alternator used in 1980 - was that the point where it changed from the 10SI (with the metal cooling fan) to the 12SI (with the plastic fan)? I've read this before somewhere, but heard conflicting views on it.

Cheers

**Terry M.** · January 27, 2004, 10:36 AM

Re: Alternator part # decoding

I am not sure of the Delco style number for 1980, but I am sure it was no longer the 10 SI. Pre-1980 Corvette alternators were Y-wound, and beginning in 1980 Corvette alternators were delta wound. This gave a greater output for the same physical size.

**theo law** · January 28, 2004, 05:24 AM

Re: Alternator part # decoding

Cheers Terry,
I've since read that the 12SI was introduced in the 83 model year. So given you say the 10SI was definitely not used in 1980, I wonder what name would be given to the correct one for my car? (11SI seems a bit too obvious, but who knows?!)

By the way, I've been having a good chat with Brian Pearce, who was telling me about your search for a vette built on the 1st of july 1980, being as this is your daughter's birthday. From my VIN, the build date of mine appears to be very close to that time (3rd july). I need to check the trim tag to be sure, but Brian has suggested that the date on the trim tag may be a couple of days earlier than the VIN sequence date. I'll definitely let you know!

My birthday was the 9th jan 1979, so I'm actually only just a bit older than my car!

I'll keep you posted..

**Terry M.** · January 28, 2004, 09:58 AM

Re: Alternator part # decoding

Theo,
Glad you got in touch with Brian. My daughter's birthday is June 20, 1980.

**theo law** · January 28, 2004, 10:22 AM

Re: Alternator part # decoding

Hi Terry

Brian must have got his wires crossed there!
Well I looked at the trim tag on my vette this morning, and it's definitely the third of July, (J3).
I'm just waiting for another response from Brian, and I'll let you know if he thinks 6 months is an "OK" gap between alternator date and build date.
Cheers!

Alternator part # decoding

Alternator part # decoding

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Debug Information