On Sun, 9 May 2021 15:41:24 -0400, Ralph Mowery
wrote:

In article ,
says...

ATC and ATO are just made by different manufacturers but follow the
same standards.




I do have to disagree with you on that. The ATC and ATO are two
different ways of making the blade type car fuses. The ATC is a closed
fuse element so that water can not get in and cause corosion. The ATO
has an opening where the fuse element is and water can get in.

NOT true. It is branding only. Littlefuse vs Bussman
ATO was available for registering - Auto was not - so Littlefuse
registered ATO as it's "auto" fuse. When Cooper Industries Bussman
division got into the market they used ATC for AT style COOPER.

There is an APR fuse that is suppose to be a replacement for both of the
above.

I have not verified it, but I am thinking the is for the blade type
fuses and they are only rated for 32 volts. I may be off on the
voltage, but it is more than 24 and less than 50 volts DC.

32 volts for 24 volt vehicular electical systems
Also APS, APM, APR and APX Automotive Protection Small, Automotive
Protection Mini, Automotive Protection Regular and Automotive
Protection Xtra for small, mini, regular and Maxi.

There is also the theory (unproven to this point) that the AP stands
for Anderson Products - another large Automotive fuse and device
supplier (now Impulse Electronics) - manufacturer of, among other
things, the PowerPole quick disconnect power connector that has
established several "standards" in the low voltage DC sphere.