02 Ford Think: Service switch/fuse panel rewire (need pic or diagram)

Ford Electric Car Forum Ford NEVs
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I specialize on Ford Thinks only, and there’s a major safety concern I have to address immediately. The 12 Volt nominal system is actually 13.0 Volts, and the negative lead from the DC-DC Sevcon converter is tied to the frame of the vehicle, hence it’s also a negative ground automobile.

The 72 Volt nominal battery pack is NOT connected to any ground, and particularly NOT the vehicle frame. The battery pack should be referenced as +72 (Positive), and 72 Volt (Negative, or RETURN), but not as ground. If you have ever notices the ‘Lightning Bolt’ icon on the cluster, that signifies an unsafe condition exists where the battery pack is sensing potentially dangerous condition where there’s a problem with the ‘isolation’.

You do not need a working DC/DC Converter for the car to charge and operate, although no ‘12 Volt’ accessories will work (lights, horn, wipers, brake lights, etc) and the Brake Icon will remain illuminated all the time. You MUST use an isolated DC-DC Converter for safety, and this will always be a 4 or more wiring connector (+72V in, 72V return, +12V out, 12 Return). You can buy cheap imported DC/DC Converters for $35, but don’t do it. It can kill you!

The DC/DC converter is NOT influenced by the instrument cluster. You don’t even need to have a cluster in the Think, or connected. You do need a working DC/DC Converter, working cluster, good fuses, working MFS switch, key switch and working DC relay, for the headlights and tail lights to work.

  1. Turn on the SDS switch.
  2. Press the brake Pedal.
  3. If the brake lights fail to illuminate, it’s 99% the DC/DC Converter.
  4. However, they may be dim. The Sevcon DC/DC Converter normally fails with only 8 - 10 Volts out, not the 13.0, so the entire 12 Volt system may be weak, dim slow, or not working.
  5. Pressing the horn switch may also show whether the Converter is working, but there’s a TSB (Technical Service Bulletin) that addresses that the horn fails all the time, and it may also be a failure in the Multi-Function Switch which sits between the horn buttons and the wiring harness. Both of these don’t require the cluster, DC Relay, key switch, etc because they are safety-related functions.

I was a massive contributor to 4dsonly.com forum before it shut down years ago.

Scott Taylor
Electrons In Motion LLC

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