More Than One 70 TCS Relay?

[Pat M.]

The TCS relay for my 70 SB 4-speed has three prongs on it, and I believe it's original to the car, even with a correct date. It is part number 3961573.
There's an auction on ebay in which the seller claims to have a relay with this same number on it, yet it has four prongs. The pictures are fuzzy so it's hard to confirm the numbers:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=330310244038&sspagename=STRK%3AMEWAX%3AIT&viewitem=

So did the 3961573 relay come in both three and four prongs? Maybe the four-prong is for an auto or different engine?
Thanks

[Pat M.]

More Than One 70 TCS Relay?

Anyone? See the picture of my relay with only three prongs, and the assembly manual shows only three wires going to the relay at UPC 7, Sheet B6. So why do all the other 3961573 relays I see (NOS and old) have four prongs?

[Jack H.]

Re: More Than One 70 TCS Relay?

When relays were purchased parts, GM typically had more than one qualified supplier. In this case, we're looking at a Littlefuse part. I think you're ASSUMING that any/all metal uprights on the bottom of the relay are 'terminals' for electrical connection. That's not a good assumption.

Here's another Littlefuse relay from a 1971 application where the bottom picture is shot with a slight angle. Note this is a 2-terminal device with a third post that acts as a connector keying lock. The purpose of the 'short' post is to prevent mechanics from inadvertantly plugging the harness connector into the relay bass ackwards...

[Pat M.]

Re: More Than One 70 TCS Relay?

Hi Jack. I get your point, that some "four prong relays" are really three prongs with an additional, non-electrical short post. That answers my question from a functionality standpoint.
But mine only has three metal uprights total. I don't even have a fourth "short post." And I have not seen that on any other 3961573 relay. I guess it's just a cosmetic difference.
Thanks for the response.

[Roberto L.]

Re: More Than One 70 TCS Relay?

Hi Jack. I get your point, that some "four prong relays" are really three prongs with an additional, non-electrical short post. That answers my question from a functionality standpoint.
But mine only has three metal uprights total. I don't even have a fourth "short post." And I have not seen that on any other 3961573 relay. I guess it's just a cosmetic difference.
Thanks for the response.

Patrick, I checked my car and it's the same like yours, three wires coming from it. See the picture.

Best regards

[Pat M.]

Re: More Than One 70 TCS Relay?

Patrick, I checked my car and it's the same like yours, three wires coming from it. See the picture. Best regards

Thanks Roberto. Does your relay have three or four metal uprights coming out the back?

[Jim T.]

Re: More Than One 70 TCS Relay?

Pat my original owner 70 still has the factory installed relay in question.
My 70's relay has four prongs. Two of the prongs are used by two different wires that are contained in one plastic piece.
The third wire by my observation could actually be connected to either of the other two prongs.
These two prongs are connected by the metal between them that lays exposed on top of the relay.
This metal piece is manufactured this way, flat metal on the relay with two prongs at each end. This is why I stated it would not matter which prong is used.
My 70 was built in July and I bought it in August.

[Pat M.]

Re: More Than One 70 TCS Relay?

Interesting Jim. As you can see from my photo, mine also has two wires that are contained in the same plastic piece.

Mine also has a metal strip that is exposed on the outside of the relay, but at the end of this strip is only one metal upright, and it appears to have been made this way.

And as I said, I believe this is the original relay from my car, down to a correct date of "4 0" for my May built car.

I must just have one unique relay, because no one has told me they have one like it.

Thanks for the response.

[Roberto L.]

Re: More Than One 70 TCS Relay?

Thanks Roberto. Does your relay have three or four metal uprights coming out the back?

Patrick, removed the wires and I see four metal spades, the innermost is the one unused and is shorter than the others. It looks like a guide but is metalic.

I took a picture today after disconecting the wires/connectors. Check it please.

Best regards

[Pat M.]

Re: More Than One 70 TCS Relay?

Mine sure seems sorta unusual based on everyone else's. Not only does mine only have three, but one of those (the incoming positive current) is the short kind. Most peculiar, momma.

[Jack H.]

Re: More Than One 70 TCS Relay?

Like I said earlier, the 'short' posts Littlefuse installed are generally intended for mating connector 'keying'... If you look at a standard electrical contact post, you'll see the contact tip is usually more narrow than the base of the contact post. That's by design to give the mating connector the proper width silhouette to grab/bite the contact post. The 'short' posts intended as keying devices generally rise only to the extent of the wider portion of the base of an electrically active contact post since they weren't intended for active electrical contact...

[Pat M.]

Re: More Than One 70 TCS Relay?

Yet in my case Jack I must use the short post for electrical contact because it's the only one I've got for the incoming positive current, and that appears to have been by design on this particular relay. And it's the correct 70 TCS Littelfuse relay, right down to the part number.

[Steven G.]

Re: More Than One 70 TCS Relay?

Pat, My 70' #9 with a/c looks identical to Roberto's relay, I think brown case is original and black must be a service replacement, something to consider. Steve

[Pat M.]

Re: More Than One 70 TCS Relay?

I'm sure that's possible Steve. But it would've been a remarkable coincidence to have such a perfectly dated service replacement put on the car, even if it was replaced very early in the car's life. I know the previous owners would not have cared enough to look/ask for one.

[Jack H.]

Re: More Than One 70 TCS Relay?

The body of the Littlefuse relay is Bakelite. When factory fresh, it's jet black and shinny (like a distributor cap). But, as the case weathers and ages, it starts to turn brown reflecting the Bakelite composition...