I've been doing some research on my '72 Supreme just for general knowledge, and I'm trying to locate the AC relay. The ASM shows two relays, but I'm not sure about what I'm looking at.

Any help would be appreciated 😀

 

From the PIM (yeah, this is 1971; the 72 is the same). Note the A/C relay is at the location shown by the orange arrows (callout 11). The other relay (blue arrows and callout 14) is for RPO C49 electric rear window defogger.

 

Thanks Joe...is there a way to test the AC relay off the car? Mine is missing the compressor.

 

The A/C relay is for the blower motor, not the compressor. If the blower works on all speeds, the relay is good.

 

Well that was easy...lol.
Thanks again Joe😀

 

Joe, is that part number 413074 or 496218?

 

The high speed blower relay is P/N 391948.
413074 is the relay for the RPO C49 rear window defroster.

 

So what are these??? I'm so confused 🤪
https://www.ebay.com/itm/NOS-1966-75...-127632-2357-0


https://www.ebay.com/itm/Relay-A-C-A...-127632-2357-0


...and is this the relay of which we speak?

 

Your confused because items on ebay are mislabeled by clueless vendors?


And yes, the relay in your photo is the high speed blower relay.

 

I waited for Joe to reply...since I was about to go postal on those ebay ads. If you recall, Dave (I hope you do) I strongly suggested you DOWNLOAD the parts catalog for your car. I provided you the link(s). Now, go and d/l that parts catalog now. The parts catalog doesn't lie. If Joe grabbed the OEM part number for you already, then you know for certainty the part number is correct (we've been down this route).

Have you downloaded the parts catalog, yet?

 

He's already posted the page from the PIM in Post #1 that shows 413074 is the relay for the C49 rear window defogger.

 

Thru 1975 - Oldsmobile Chassis and Body Parts Catalog

Grab this while you're at it:

Thru 1975 - Oldsmobile Illustration Catalog

 

And unfortunately, here's the problem with using a newer parts book edition.

The parts book excerpt I showed in Post #7 is from the January 1972 printing.




From the June 1975 Parts History Catalog, the correct 391948 relay was discontinued in July 1973 and was superseded by P/N 412687.




But wait, it gets better. In December 1981 Parts History Catalog, 412687 was discontinued and replaced by 413074. All of these relays are comparable in current-carrying and are physically interchangeable.




And finally, the November 1979 edition of the parts book also shows 413074 as the only available relay that has superseded all other part numbers. That doesn't make it "correct", it just means that this was the closest usable part that was still available in the parts network (the same parts book shows "J" heads for use on all BBOs).

 

All good info guys and thanks. So here's where I'm going with this thread...I'm working on a stockpile of OEM or NOS parts and my next goal is the AC relay,...will this one be the right replacement should mine ever go south?
https://www.ebay.com/itm/NOS-1966-75...-127632-2357-0

 

413074 will work. It won't be optically correct if anyone checks the part number. Frankly, it's no different than using a quality aftermarket replacement. Neither one will be the original, "correct" part. Both will look "correct" to the casual observer. For example, Standard Motor Products RY8 replaces 391648, 412687, and 413074 for about $13 at RockAuto.

 

I getcha Joe, but aren't we also talking Chinese made vs US made? Also, you have more knowledge about this stuff than I could ever dream to have, so based on your experience, how often have you seen these (and other 50 yr old) electronic parts go bad? IOW, is having backup electronic parts something I really need to worry about?

 

The blower relay definitely goes bad. The relay contacts pit, resistance goes up, the contacts heat up, and eventually they stick together and the motor won't shut off. I've had this happen twice. Your call on the GM part vs. the SMP part. Standard has always been a good brand, but like everything today, manufacturing has moved offshore. Just stay away from their low-rent "T" series parts, where the part number has a "T" suffix. Those are crap.

 

Having spent considerable time in the IT industry, some (quite a few) years ago I had some conversations with individuals well versed in production of electronic/electric components. This conversation began with my questioning the manufacturing of RAM (primarily) modules - both buffered and non-buffered. Aside from country of origin, I learned what the "T" stood for in the manufacturing process. I won't bother you with the various types & certification of RAM modules. The "T" stands for tape-and-reel packaging. Tape-and-reel packaging is a form of manufacturing processes of electronics/electrical supply components - I SHEET you not.

 

I'll be done with it, but since it was brought up, here's the annoying little piece of information regarding the "T" suffix (as an example when an electronic/electric part is produced/supplied/packaged/manufactured/assembled - pick your choice of term):

I could go on to produce many manufacturers who employ TAPE AND REEL PACKAGING, but this is not the thread to do so. There's plenty of "interwebs" information regarding TAPE AND REEL PACKAGING and part numbering.

 

Norm, what the heck does tape and reel packaging for individual electronic components used in a mass production pick and place assembly line have to do with a finished part that has a T in the part number?

I think the answer is: nothing.

 

If your original relay casing is in good condition you could replace the guts from a newly purchased relay.
You will just have to take your time to unbend the tabs holding the electronics in both relays and then inserting the new electronics into the old case and sealing back up by re-bending the tabs.

 

Yeah, I was going to say the same thing. I'm pretty sure that Standard Motor Products isn't using tape and reel packaging on their "T-series" distributor caps or voltage regulators or oil pressure sending units.

Here's an example. DS177 is their regular quality headlight switch. DS177T is their "economy" quality switch. Neither has anything to do with tape and reel packaging.

 

Good question, you've actually partially answered the question - the key is "mass production".

So, this is the skinny as I was told and based upon just a little research in which I convinced myself over the years the newsworthy commentaries of my colleagues with much more experience in the actual hardware production of part numbers in the electronic/electrical industry were in fact, true.

There are MANY forms of manufacturing/assembling of electronic/electrical parts. Historically the manufacturing of these items was shall we say "analog", not a bad way to describe it. In the early years, let's use computers as an example, or TVs, or RADIOs, etc. we began with simple tubes and tube arrays which controlled various functions with no board circuitry. It was a mechanical means to electronic/electrical engineering in which, here is a key, parts were certified - a very, very time-consuming labyrinth of labor - but, one which achieved a very high non-failure rate.

Times changed, technology changed, manufacturing of electronic/electrical components migrated from analog/mechanical arrays to digital formats employing board circuitry e.g. recall the early RAND computers, tube TVs, radios, cars, etc. Enter the digital world and board circuitry. Early endeavors had essentially one marketplace - that was to make the best non-fault electronic/electrical components where each received a high degree of certified bench-testing before they left the manufacturer. Move further along in the history of digital engineering and you arrive at the silicon wafer chips (the area I have the greatest familiarity). In the many and various technologies which have migrated into the digital age (the largest of which was the PSTN - Public Switched Telephone Network), but lets include include EVERY single facet of our life, the production of electronic/electrical devices has had to keep abreast with demand. Enter the various "types" of mass production of these components.

Perhaps the best components, components which would not be purchased for say an Ariane 5 rocket to send the James Webb telescope 1,000,000 miles distance from the Earth, would not have part numbers with a "T" suffix. None-the-less, the circuitry includes both electronic and electrical circuit boards with components derived from silicon (ingot) components and nano-components made by select manufacturers who also produce many of the same components.

Let's use RAM as an example. There are literally hundreds of millions of various electronic/electrical components produced to satisfy various industries. MIL-SPEC manufacturers (as and example), medical device manufacturers, etc., etc. will NOT purchase part numbers with a "T" suffix because there is no or extremely limited validation/verification/certification of the components employed in the manufacturing process. The same manufacturers can and do produce the EXACT same model number device assembled in absolute MASS quantity employing tape-and-peel manufacturing. These let's call them "T" components are heavily mass produced with (in many cases) no warranty, limited warranty, no certification - mass produced for the masses. The cost of manufacturing is pennies compared to non-tape-and-peel production. It' far cheaper for a supplier to replace a bad piece of technology designated "T" than to manufacture the exact same component without tape-and-peel ("T") technology. The "T" designation also produces a formidable line of manufacturing fault/non-fault history of manufacturing. So, back to RAM and computers, telephones, etc. and the like - many manufacturers employ components produced via tape-and-peel technology at in many cases 70% - 80% less production cost than the exact same component produced without tape-and-peel technology.

 

And, that is a valid point. I'm not a manufacturer of anything. I did perform a little research on the development and notion of tape-and-reel manufacturing when I was in IT, and as I suggested, when questioning the manufacturing of RAM (primarily). My answers were drawn from experiences working with colleagues at Philips Electronics, Cisco, 3-COM, INTEL, Nanya Technology Corporation, Samsung and the like. If you have the occasion to examine parts labeled "T" in the IT industry, you'll find replete instances of the exact same component part number identified with and without the "T" designation.

 

Norm, your lengthy post #23 above is not quite correct. I work at an implantable medical device manufacturer and ALL of our components are tape-and-reel in order to facilitate automated parts pick-and-place; it has ABSOLUTELY nothing to do with the quality/reliability of the components. ALL of our parts are higher than MIL-spec quality as they go into life saving medical equipment, and they are ALL tape-and-reel so that they can be placed by the automated Muehlbauer pick-and-place equipment.

 

Kenneth - As stated, I was informed the "T" suffix related to mass production of electronics/electrical components employing tape-and-reel technology. I was also informed it did in fact have everything to do with reliability, certification, quality & longevity. Perhaps your company purchases those components and they're excellent - how am I to say who purchases your components, I guess they work.

 

And the nonsensical BS continues........

 

A petulant remora………………

 

By someone with inaccurate information, or your recollection of the information is inaccurate. The T suffix merely designates the packaging method, which is whatever the buyer specifies for that particular component. The packaging has no correlation to the quality level of the part.

 

You may have a point and I suspect I should believe you and that’s fine. Yet, in the field of RAM module production, I know for a fact industrial applications of RAM modules are labeled differently with the suffix “T” representing lesser quality mass produced, non-certified assemblages. These components are regarded as consumer products. They are employed in consumer production as opposed to precise certified industrial applications. It’s unclear to me why a Cisco hardware engineer would state to me there are differences in quality of production materials and lesser quality components designated via the suffix “T”. Maybe these folks don’t know what they’re talking about? I can attest when it comes time to purchase RAM modules those listed with a “T” are not within the approved parts numbers for purchase while those without the “T” suffix are approved for purchase at anywhere between 100 to 1000 times the cost for the exact same number but w/o the “T” suffix.

I only brought up the topic because I noticed Joe mentioning to stay clear of parts numbers ending with the suffix “T” (read above) - that was not my statement. Perhaps this is industry based. Perhaps technology has advanced and assembly packaging production has improved greatly and within select industries. I’m not a manufacturer, I’ve purchased significant quantities of both precise industrial IT components (primarily RAM modules) and consumer based RAM modules for 100,000+ employee organizations. Evidently I was fed a bunch of mumbo jumbo. I guess it’s all whimsical nonsensical BS not worth engaging in conversation. I remain curious as to why an automotive part is labeled with and without a suffix “T” and why the suffix “T” equates to crap?

 

And even less correlation to automotive components sold by Standard Motor Products...