Last update: Apr 13 2017


This page describes the additional wiring added to support the new 12V components as well as the high voltage accessories.


Wiring Diagram

The AUX IG RELAY provides 12V power when the ignition switch is turned on. It is redundant to the car's ignition relay to avoid taxing any existing circuits.

The DC-DC converter input includes a diode and inductor to protect it from voltage sags and oscillations, respectively. The diode idea is from EVTV. The inductor is recommended in the Evnetics FAQ "Why does the fuse to my DC/DC converter keep blowing whenever I accelerate?"

The high voltage circuits, except for the controller, are controlled by Gigavac P105 contactors.

Fuse Box

Many of the new components are contained in an auxiliary fuse box I added to the right hand side of the engine bay, where the air intake was.

Aux Fuse Box Aux Fuse Box Aux Fuse Box Aux Fuse Box

The 12V fuses and relays are plugged into a fuse and relay block called the Cooper Bussmann Rear Terminal Mini Fuse & Relay, purchased from Waytek Wire. I'll rarely be submarining, so no waterproofing seals or cover.

Cooper Bussmann 15303 Cooper Bussmann 15303 Cooper Bussmann 15303

The fuses and relays attach to the wires using Delphi Metri-Pack 280 series female terminals, so a crimper is needed. The GM Delphi Weatherpack Crimper Tool is relatively inexpensive and works fine.

Terminal Crimper

For making connections, I attached six 6-pole Wago Lever Nuts to the sides of the fuse and relay block using heavy duty double stick tape. Two are for unswitched power, two for switched power, and two for ground. These devices are easy to use and compact. Perfect for fixing mistakes and changing your mind.

Wago Lever-Nut

Part Numbers

EnclosureHammond Manufacturing 1444-10825 and 1434-108
12V fuse and relay blockCooper Bussmann 15303-4-0-4
12V mini fuse 5AWaytek Wire 46261
12V mini fuse 10AWaytek Wire 46263
12V micro relaySong Chuan 301-1A-C-R1-U03-12VDC
High voltage diodeSTMicroelectronics STTH200W06TV1
High voltage fuse 1/4" x 1-1/4" blockCooper Bussmann BK/S-8301-3-R
High voltage fuse 1/4" x 1-1/4" blockCooper Bussmann BK/S-8301-1-R
High voltage fuse 1/4" x 1-1/4" 30A (heat, A/C)Littelfuse 0505030.MXP
High voltage fuse 1/4" x 1-1/4" 10A (DC-DC)Littelfuse 0505010.MXP
High voltage fuse 1/4" x 1-1/4" 315mA (JLD404)Littelfuse 0508.315MXP
High voltage inductorBourns 1130-101K-RC
High voltage contactor 50AGigavac P105
Junction blockVTE 77025N02
Spacers under relay blockEagle Plastic Devices 561-kSP166
Splicing connector, 5 conductorWago Lever-Nut 222-415
Solid State RelayCrydom DC400D20

Ignition Switch Power

The AUX IG RELAY coil is fed by the vehicle speed sensor power wire, which is a convenient source of ignition switched power near the center of the fire wall. The VSS connector B17 color is gray in the service manual, but actually black in the car. Very confusing because it is right next to another gray connector with the same number of poles (connector B128).

The DC-DC output relay coil is powered by a different ignition switched source. Connector F60 is located conveniently close to the 12V battery, where the DC-DC is located. Pin F60-4 originally provided power to the ignition coils.

Engine Grounds

The IC engine block itself forms part of the electrical circuit. It has several ground connections, one of which is for the fuel level sensor, vehicle speed sensor, and the instrument cluster. With the IC engine removed, these connections need to be replaced. I recommend grounding these wires at the connector nearest the engine (F60 in the diagram below).

Wiring Diagram

Keep your ECU

I recommend leaving the ECU connected and leave as as much of the existing engine wiring in place as possible. In order to remove the clutter of the engine wiring harness on the passenger side of the engine bay, I removed the wires all the way back to the ECU and removed the ECU itself. It was a decision I came to regret. I cut off the connectors to the ECU only to find that some wires unrelated to the IC engine are spliced together near the connectors to the ECU. Thus, I inadvertently severed several important connections. Additionally, it would have been much easier to identify wires leading to the ECU with the connectors still attached.

ECU Removal ECU Removal

One problem that resulted from removing the ECU was that the keyless entry unit malfunctioned. This was perplexing and time consuming to diagnose. I eventually discovered the culprit was the immobilizer control module, which was not happy without the ECU. The problem was solved by disconnecting the immobilizer. The specific problem is that the immobilizer produces 10V on pin B141-26 (WR), which is connected to the key warning switch B370-2 (WR). This connection is not shown in the service manual wiring diagrams. The immobilizer pin B141-8 (Y) is also undocumented.