Let's dive into the power distribution module (PDM) a bit...
First, here's some "old school" relays and circuit breakers. These are "mini" relays and what is still included with most relay kits for fans etc. But, that's not what OEMs use anymore. They take up way too much space. Shown here on a piece of aluminum for reference.
Here's a modern upgrade using the current micro relays and mini fuses that have the same ratings as the larger stuff. In fact, this little box can fit 6 relay and 12 fuses/circuit breakers. This pic shows 3 30 amp circuit breakers and 6 relays as one layout possibility. Compare that to the above which is 4 relays and 4 fuses/circuit breakers. In fact, I can fit 2 of these little boxes and have room for up to 12 relays and 24 fuses. The are fully configurable so I could fit 30 fuses in one box if I wanted. I will note now, the ECU power does not run through here. It needs to be wired to the battery and not in a PDM. This provides the cleanest power for the ECU which needs the cleanest power it can get. So the ECU runs over to the battery through a MAXI fuse. I also am tying the vintage air 12V line in with the ECU as it needs clean power too since it's running digital logic just like the ECU.
Here's the backside of the PDM I'm building, showing 2 bus bars, one for 12 V and one for ground. Both will be wired directly to the battery. Ok, the 12v will go through a 200 amp fuse with the alternator. Obviously no wiring just yet, however, I did complete the layout tonight. With the 2 boxes, I have loads of free space for future needs. I'm currently planning 6 relays (3 fans, AC, Head lights i.e. low beam and high beam), 3 circuit breakers for the fans, and 8 fuses for additional circuits. I'll finish up the fab work on the panel and get some paint on it then wire it up.
