olds70supreme

Hello,
What is the "best practice" way to add circuits for non-stock accessories? I am installing a vintage air unit in my 68 Cutlass and need a source of switched power. If I was younger I probably would have jabbed a spade terminal in between the fuse and fuse holder.

I've seen aftermarket "add on" fuse blocks that give 5+ circuits, but these will still need something to trigger a relay to turn power on when the key is on.

I'm looking for advice on the best way to get this power, and if an addon fuse block is the best way, what are the best places to mount it? I'm trying to keep the non-stock aspects of my car as hidden as reasonably possible.


Thanks in advance.

joe_padavano

How much current and how many circuits? The factory fuse box has terminals for IGN (powered with key in RUN), ACC (powered with key in RUN and ACCY), and BAT (powered all the time). These max out at about 20-25 amps. If you need more, use a relay with a separate fuse or breaker wired directly to the junction post on the horn relay and controlled by a wire to the IGN or ACC terminal on the fuse box. This is how the factory wired high current accessories like power windows or seats.

olds70supreme

Wow, now I'm mad at myself. I just realized that the old HVAC controls had a brown power wire that gives me a convenient, non-modifying source of power that is already right where I need it. Now if only I had made that realization before posting and letting everybody else know that I missed it

oldcutlass

But you still learned something, so not a loss.

joe_padavano

But what's the total amperage of the VA unit, both compressor clutch and fan motor? That HVAC circuit is fused at 25A. Looks like the latest VA units require both that HVAC feed and a separate connection to the battery (or horn relay terminal) to feed the 30A circuit breaker.

olds70supreme

Not sure, it is a 14 gauge wire (same or smaller than the stock wiring it will connect to). As you point out the heavy amp loads are fed through a separate feed from the battery.

oldcutlass

Use the brown wire to trigger relay/s to power a separate fuse panel for your a/c and any other things electrically you'd like to add.

joe_padavano

Note the wiring diagram above. The brown wire feeds the Vintage Air ECU. There's a separate wire out of the ECU that triggers the relay as needed. That's similar to how the high speed blower relay works on the factory A/C.

coppercutlass

I use stand alone fuse panel and relay panel for my accessories outside of stock stuff.