30 Amp fuse holder
 

My '72 Trans Am without A/C has the 30 amp fuse holder attached to an alternator wire. I thought that was for A/C cars only.

A few years ago Restore a Muscle Car sold a very similarly equipped original 4-speed T/A without A/C. Attached is a photo from the sale that clearly shows it too has the 30 amp fuse holder.

I hope someone can help determine why they were on these cars.

I thought it was for the high speed in the fan/climate controll.

Electric grid rear window defogger?

My 71 is a non-AC, blower defogger car with original engine harness and has a white 30 amp fuse holder. Ignore the black fuse holder in front of the valve cover. That’s a battery tender wired to the alternator + terminal.

Not on a 10si..
This car has a ac engine harness probably. Look behind pass head for more unused wires

I learned about the 30A fuse holder on my '73 in this thread.

https://forums.maxperformanceinc.com...34#post6200434

I suspect it will answer your own question. There is a linked thread within it that may also provide answers. Mike (Held For Ransom) was a big help to me understanding it.

30A (white, twist top) is probably a standard harness and for the AC that is not there.

30A fuse holder
 

I've been working with American Autowire to figure this out. I learned from the '72 GM service manual that the "A" body harnesses contained the 30A fuse lead that exits the engine harness back near the TCS connector. However, the service manual schematic for the "F" body does not show the wire/fuse assembly. So, my non A/C 72 T/A did have the connector that exited the harness back by the TCS connector but was obviously never used (dirty and the plastic on the end of the connector looked a little melted).

BTW, my harness had a tag on it that read "0484" "RL". I strongly suspect the 0484 is the last 4 of the part number (perhaps 8910484??) and the RL would be a build sheet code. If anyone has more info on the "0484" part number or a build sheet that contains "RL", I'd like to learn more.