MGA! Tech Talk – September/October 2025
Tech Talk
with Bob Shafto, Technical Editor
Hidden USB Power Adapter
I have had a USB auxiliary power adapter wired into my car for a while. However, it is a hassle when I need it because I have to fish it out from under the dash and then it takes two hands to plug in the USB connector for my phone. At least it served the purpose while I contemplated a way to attach it to the dash and be able to fold it back out of view. There were a few details I needed to figure out. First, it would have to have a hinge and a way to keep it from folding when plugging in a USB power cord. Another issue is it would need to be removable and leave no trace that it was ever there (this means no new holes). After giving thought to various designs and locations, I settled on a hinge with a locking arm mounted to a magnet base and a right angle mounting bracket for the auxiliary power adapter.
The ideal location seemed to be at the bottom edge of the dash between the heater controls and radio cutout, this placed it out of the way of the shifter and other obstacles.
The auxiliary power adapters come in a variety of configurations, the one used here is 56w, has two standard USB connectors, one USB Type C, inline fuse, a volt meter and a power On/Off switch.
The selected hinge is Fath # 095KF3030F00 Polyamide, Series: 30, Overall Width: 59mm with locking lever. The magnet is a Magnetpro 66mm – Strong Rubber Coated Anti-Scratch with 65 lbs of Adhesive Power. It has a 6mm threaded hole in the center. The Magnet, hinge and power adapter cost is about $30.00.
To mount the hinge to the magnet, you need to drill and countersink a 6.6mm hole near the edge of the hinge for a M6-1.00 x 16 Flat head screw. This will require some reinforcement. First fill the hollow areas on the back side of the upper hinge plate with a structural epoxy like JB Weld. While the epoxy sets, make the reinforcement plate and mounting bracket. When the epoxy has set, file or sand it flush to the hinge plate.
Next mount the reinforcement plate to the upper hinge plate, using two 10-32 pan head screws and trim them flush to the reinforcement plate. Now use the 6.6mm hole in the reinforcement plate as a guide to drill a 6.6mm hole thru the hinge plate (be sure to keep the drill perpendicular to the reinforcement plate) and countersink the hole on the front side of the upper hinge plate.
The power adapter comes with a two-wire harness and a 10amp, inline fuse. The black wire must be connected to the negative side of the battery so if you have a negative ground car, connect it to the knurl nut on the back of the fuel gauge with the dash harness grounds. Cut the ring terminal off the red wire and connect it to the A terminal on the lighting switch.
If you have a positive ground car the red wire goes to the knurl nut on the back of the fuel gauge and the black goes to the A terminal on the lighting switch.
Hack: The brown wire for the horn button has battery power except while the button is being pushed. It also has a bullet connector so the single barrel connector could be changed to a double barrel and the power wire for the power adapter could be terminated with a bullet and connected with the horn button brown wire.
The adapter will lose power while the horn button is being pushed, but power will return when the horn button is released. This is much easier than connecting to the A terminal on the lighting switch.
