deciphering Julian Codes

[theo law]

Since buying the technical info guide for my 80, I have been looking around the car to see what parts are correctly dated. I know this isn't exactly a chrome bumper car with 12 original miles, but I'm still keen to quanitify how much original stuff is still present!
According to the guide, the horns are dated with a Julian code. The horns I have are the correct part number, and the Julian codes appear to be 610 and 520. Perhaps this would initially suggest days 61 and 52 of the year, but the guide has a section on Julian code layout that puts the zero FIRST for the two digit dates, ie these days would/should be 061 and 052. However this part of the guide is specifically referring to carb dates - what do my numbers mean to you more knowledgeable people??
Cheers!
Theo

[Guest]

Re: deciphering Julian Codes

I just looked at the Julian Codes in the carburetor section for 68-69 and the last number is the year code. Your dates would indicate days 61 and 52 of 1980.

[theo law]

Re: deciphering Julian Codes

Ok, so I guess if the date to be represented was after the 99th day, the code would move up to four digits, eg 1050? I was thinking the code was only 3 digits long and didn't reflect the year in any way. Well that's two more parts that match up nicely, which is always good!
Thanks for your help!

[Terry M.]

Re: deciphering Julian Codes

Julian codes can be devilish. Some items have the year first, others the year last, and just to make it more fun some parts changed the pattern. That is for part of production the turn signal flashers had the year first, and then suddenly they changed to the year last. I guess whatever the code is was known to those dealing with the parts at the time. Our challenge is to figure out what that code was all these years later.
PS: Don't always think in terms of the day of the year. While it is not strictly speaking a Julian code, tires (after 1971) are dated in weeks of the year.

[theo law]

Re: deciphering Julian Codes

Hi Terry,
I have to assume that, since these particular codes are 610 and 520, then they must refer to days of the year? 52 would work for "weeks of the year" but clearly not 61....
Have you had any experience of horn Julian codes? Do you think we are right in our above interpretation?

[Terry M.]

Re: deciphering Julian Codes

Theo,
My experience with horns is from a decade earlier than your car. I have nothing to base an opinion on regarding a 1980. I agree that they are probably days of the year, especially given the 61. I mentioned weeks just to point out that one must keep an open mind when trying to resolve date issues.
Have you looked at the 1980 Technical Information Manual and Judging Guide? That might tell you what the date code should be. Using earlier manuals, or the codes on other parts can lead one astray.

[theo law]

Re: deciphering Julian Codes

I appreciate your mentioning of week numbering as a reminder to keep an open mind :-)
Yes, I have looked in the TIM, but it gives Julian codes for other parts but not the horns. I think an educated guess would say that the numbers are days of the year and the "0" means 1980 - especially seeing that these are the orignal part number and "note", that interpretation would make the most sense. I just wondered if anyone would chime in and say "yes, those numbers DEFINITELY mean x,y or z...."

Good to have a chat with you again, cheers!

[Chuck S.]

Re: deciphering Julian Codes

Theo, there are always exceptions, but I would say that it is highly likely your horns are original. Unless failure is preordained by poor workmanship or bad design (evidence of chronic replacement in that MY), horns are a really low stress, low use part that are almost impossible to abuse.

Good question on the Julian dates. I knew about the variation that Terry mentioned, but my inclination was toward day of the year being three digits, with an additional digit for the year. I thought I would wait and see what others had to say.

If you get the chance, a close inspection of horns (if you can see them) on original cars at a regional meet is a good way to confirm your information.