E12 Blade Fuse Retrofit Kit Install Tips
The E28 blade fuse retrofit kit is compatible with E12-based cars, however installation varies slightly due to minor differences in the fuse box frame in some models. Below are some notes from a customer who installed a kit in an E12 as a guide.
E12 Blade Fuse Box Upgrade Notes
Robert Bondi
Installation of the blade fuse circuit board on an E12 (77 530i) was straight-forward using the E28 information guide. A few techniques, extra notes, and differences are documented here in this supplement.
To enable rotation of the fuse box to work on the underside, the E12 has a grommet that passes two wires into the box as shown in Fig. 1 that should be removed. These wires connect to fuse 14 and 17. I disconnected these wires, pushed the grommet outward from the box, and set them aside.
There were 5 soldered connections as shown in Fig. 2 that go to fuses 3, 6, 8, 13, and 15. All of these were soldered to the input side of their respective bullet holders. Carefully, cut or heat release these wires for later.
Work hardening is very effective at removal of the bullet fuse holders; however, work hardening is difficult for the holders that have thru-terminals on both ends. In these cases, I found it effective to first drill a tiny hole with a Dremel drill bit (1/16” or 3/64”) at the blade ends where there is a small barb as shown in Fig. 3. This aids in release of the barb at the drill hole.
For installation of the blade fuse circuit board, it was necessary to open slots at the fuse 2 and 3 outputs and make a hole for the LED ground wire.
The grommet makes an ideal access point for installation of the LED ground wire later.
The biggest surprise for the E12 installation was the discovery that the blade fuse circuit board blocks the front mounting screw for the fuse box as shown in Fig. 4. While the three plastic pillars also appear present for the E28, they only seem to be resting mount supports on the E28, while three long sheet metal screws are used on the E12 to join the fuse box top and bottom together while also holding the assembly to the underlying sheet metal in the engine bay. Rather than completely abandon the front screw, a compromised solution is possible without considerable effort. By enlarging the hole in the front pillar to atleast the diameter of the screw head, it is possible to use the screw to fixture the fuse box bottom to the sheet metal and still have the fuse box top sit flush as shown in Fig. 5. An Allen head bolt and nut solution is also possible here, since there is access to the rear hardware at the front mounting point. Figure 6 shows the compromised solution for the front mount before seating the fuse box top side.
Like the E28, fuses 4, 5, and 17 LEDs will be lit with the key out of the ignition when everything is rewired and battery reconnected.
Fig 1. Grommet with pass-thru wires into the E12 fuse box.
Fig 2. Locations of soldered wire connections on an E12.
Fig 3. Small holes drilled at terminal blade end slots to aid release of bullet holders.
Fig 4. Direct comparison of blade fuse box upgrade (left) and the bullet style fuse box (right). The blade circuit board covers the front screw mount point.
Fig 5. Drill out the screw hole in the front pillar so the new hole is large enough to accept the mounting screw head. Blade fuse circuit board is seen through the enlarged hole.
Fig 6. Nearly complete installation on the E12 showing both the compromised use of the front screw mount and LED ground wire passing through the front grommet on the left.