Proliferation of Car Part Numbers

[George7941]

I will use GM (Delco) relays as an example since I am familiar with them but this applies to other manufacturers and other parts.

There are so many different relays used for typical relay applications --- starter, fuel pump, lights, horn, ignition etc. The part nos. vary with the application and also from year to year e.g. starter relay for a 1998 model will be different than the one used in the 1999 model.

Now, relays are not very complex. All the ones we are referring to are 12v relays. Desirable characteristics are
Low coil current
High current rating for the contacts
Low voltage drop across contacts
Small size
High mechanical reliability

So why doesn't Gm just standardize on a few high quality relays? Say, 150 ma coil current and a 30 A contact rating in a mini can size. With standardization comes economies of scale and Delco will be able to provide a smaller array of higher quality relays.

While I am not an electrical engineer, I don't think the different GM relays are all that different and they really do not need so many different ones.

I can see why a reverse light switch from one transmission might not work well on another transmission since thread size, travel, clearance etc might be different. But as for relays, there just are not that many variables

 

[d00df00d]

Good question. I suspect there is a very sensible and yet not altogether comforting answer.

 

[MolaKule]

The higher the current, the larger the contacts need to be. There are limits to the "current density" for any contact. The larger the contacts, the larger the mass needed to "throw" the switch contacts, so higher currents are needed, therefore, the field coil has to use more current (to create a greater magnetic field strength for "pulling-in") and has to be itself larger.

 

[George7941]

Molakule, I agree with all your statements.

My point is that the differences are not significant enough to warrant using so many different relays. If they standardized more , they could use higher quality relays where they are using lower quality relays now and it would not cost any more because of the savings to be had by having far fewer part numbers.

 

[The_Jeff]

You'd like my saturn; all the relays are the same except the DRL one has an extra tab to pass current when resting.

What's dumber than anything is when you read a GM owner's manual and the "starting instructions" say to look up your engine in the VIN, then follow this part of the manual-- but all it says for every motor is don't touch the gas, turn the key until it goes!

I remember back in the 80's when car wiring was mostly spade terminals arranged in plastic blocks-- so in a worst case scenario, one could rewire with off-the-shelf spade terminals.

 

[brianl703]

A bunch of the relays (horn, fuel pump, headlight, foglights, etc) listed for the 2004 Chevy Malibu Classic are listed as follows:

ACDELCO Part # 1550688 {4-WAY-SPST-280 MICRO #12088567, 1580453, 158571, 19115080}
RELAY,HDLP CODE 3412
RELAY,HDLP 4 TERM, 280 MICRO, HI-PWR, W/RESISTOR, UNSHROUDED, GRAY

I find the same relay used for a few applications in the 2001 Chevy Cavalier.

I suppose that #12088567, 1580453, 158571, 19115080 are the OE part numbers this AC Delco relay replaces. Of these, only 19115080 works, the other 3 come up as a discontinued/unknown part.

 

[brianl703]

How about furnace control boards? Goodman/Janitrol has used B18099-06, B18099-08, B18099-10, and B18099-13. B18099-13 is supposed to replace all the preceding ones(which are no longer available), but I replaced a B18099-06 with a White-Rodgers 50T35-743 which also replaces all the B18099 parts.

I think what seems to be proliferation of part numbers is often because old parts and numbers are superseded by newer (presumably improved) parts with newer numbers.

 

[bdcardinal]

Originally Posted By: brianl703
I think what seems to be proliferation of part numbers is often because old parts and numbers are superseded by newer (presumably improved) parts with newer numbers.


bingo. you would be amazed how fast part numbers supercede with ford especially.

 

[Rabbler]

A change in vendor can also trigger a part # change.
Some relays also require a spike suppressing diode if they are computer controlled.

 

[Papa Bear]

Once you get the relays straightened out, maybe we could have 3 or 4 different oil filters as well, not hundreds.

Of course, GM is going to make a part, then keep fixin' on it (with different part numbers) until it doesn't work right.... and then KEEP it.

 

[George7941]

"Some relays also require a spike suppressing diode if they are computer controlled."

Then why not have the diode in all the relays? IIRC, at DelCity, the relays with the diode are the same price as the ones without the diode.

The explanation about supercession of part numbers makes sense and probably accounts for a large percentage of the different part numbers.

 

[bdcardinal]

Supercession is the most difficult thing to explain working in a parts dept. Sometimes the new part looks a little different and may require a jumper harness to work. Sometimes they are made of a different material, such as an engine mount or a suspension bushing. For some vehicles they have updated spark plugs due to issues that dealers see, i get a lot of shops complaining about that. Usually sources like alldata do not update so we have to print out the TSBs or SSMs.

 

[brianl703]

Originally Posted By: George7941

Then why not have the diode in all the relays?


Relays with diodes in them are polarity-sensitive. Relays without diodes are not.

 

[George7941]

Good point! With most relay blocks on cars, you can turn the 4-pin relay around 180 degrees and still plug them back in. It would blow the diode if done with a diode-equipped relay.

I suppose one way to prevent this is to use 5-pin relays even when the fifth pin is not needed.