Okay, so I'm wiring up my latest mod (electronic cutouts) and it doesn't work. Lights come on, using the switch or the wireless fob cause the lights to flash, but motors do not actuate.

I was surprised to see that the volt meter only reads 8 V on my new circuit (but 12+ V at the battery). I'm using one of those add-a-circuit things in the BCM fuse box (passenger foot well) in fuse position 22. I also tried position 18, same results. When I test from the supply of the add-a-circuit (only one tab of the fuse in) to the ground (bolt just above the left side of the fuse panel), I get 12 V, but as soon as I install the fuse properly to power my accessory, I see 8V on the meter (for that circuit only).
Anybody have some experience with automotive wiring that could point out some condition that reduces the voltage by one third? Could it be a bad wire splice (poor contact)? I thought those generally gave you 12V but overheated quickly and fried the wires... All splices are crimp connectors, BTW, no vampire connectors here.
I've left a message for the vendor, but I was hoping someone here could help me out.