Hi All,
Steve, yes, many manufacturers have centralized protection centers for fuses, relays, and diagnostic computer plugins and, due to their electronic complexity, were designed that way. Our Healey harnesses were not and operating amperage for all devices are carried and controlled with elements directly wired into each circuit (i.e. Headlight Circuit, etc.).
Although this was not as much of an issue with few attached devices of low draw, many of us have added many more devices that have dramatically increased the amperage draw through circuit wiring. With aging, corrosion, and hardening, additional resistance results in increases in even the original equipment amperage draw with harnesses required to carry more power flow. Adding upgrades and add-ons through the same harnesses have caused many to exacerbate the situation with the switch from their original 23-amp generators for a 65+ alternators in order to meet the power demand.
So, what are you trying to protect? If you are installing relays to reduce the amperage flow through your harness from operational draw to that of switching only, I would suggest you place the relays closer to the device and create a harness to the nearest source of high power (i.e. generator/alternator). As with fuses, if you want to protect the circuit, place the fuse at the power source of the circuit but if your intention is to protect the device, place the fuse close to the device. Keep in mind that, in most cases the Healey's circuits and devices are not fuse protected and running additional wire to a central point only extends the circuit for questionable access convenience. Also, with a fuse block, you are limited what it provides. However, you can centralize critical components and compliment with the use of in-line fuse protection on all other circuits and components you wish to also protect. Although this combined approach will eliminate any limitations, it does require the creation of additional documentation that references the circuit and its location of fuse protection to ease future location.
Since all my relay and fuse connections are lubricated with dielectric grease and weather tight to eliminate moisture penetration over the substantial extended time of forgotten attendance, I trust the small benefit derived from a central fuse box and/or relay box is far less then the accepted limits.
Just my thoughts,
Ray(64BJ8P1)