Models: all, Years: all

As you know the Pinz has a main power switch located between the driver seat and the door which connects the negative pole of the battery to the chassis. This is a good way to protect the batteries from accidental discharge but it presents a big risk for the alternator circuit (rectifier and regulator). If the switch is opened while the engine is running the rectifier and/or regulator would be shot in milliseconds. To avoid this problems the engineers at SDP designed a bypass circuit with a relay. As soon as the alternator delivers voltage/current the relay is activated and bypasses the main switch. With this circuit you can open the main switch and nothing happens unless......... the circuit is dead or the relay contacts get overloaded. This may occur if a lot of extra electrical circuits are added to the Pinz. In addition the relay is mounted in a very hidden spot but extremely exposed to the elements. It is located on the sheet metal between the engine and the battery box. If you are able to squeeze your head through the opening between the cylinder heads and the floor or between the battery box and the frame (from underneath) you may have a chance to see the relay. It’s a simple 24V relay and, if I read the marking correctly, rated for 20A only.

After 25-some years the relay and the connectors may be really tired so it’s a good idea to check whether the circuit is still functional. As it may be a bit too expensive to just turn off the main switch with the engine running and wait for what happens I want to describe a method to check it “destruction free”. What you need is a 24V power supply and a Ohmmeter (DVM).

Disconnect the battery (best on both sides) and hook up the Ohmmeter between the negative battery connector and the chassis. The main power switch has to be in off position (take the NATO-bone out). The meter should show an open circuit, if not: your main power switch is toast or the bypass relay contacts are frozen together. If this is the case disconnect the wires from one side of the main switch and measure the resistance between the two sides of the switch. Open it should show infinite resistance, closed not more then about 1 Ohm (if it shows more you will need a new switch).

Remove the doghouse and search for the light-blue wire(s) in the Molex connector close to the alternator. Pull out the one which doesn’t go to the regulator and connect it to the plus of your 24V supply. My preferred way is to open the connector, disconnect the light-blue wire from the regulator and connect the power supply to the Molex connector (less effort and checks the connector too).
You can use the batteries for this but they have extreme current capability so you better be careful! I prefer to use a power supply with a max current of 1A as it doesn’t contain as many “smoke genies”....... As soon as you connect the negative side of your power supply to the chassis you should hear a little click from the relay and the Ohm meter should show a short (if you didn’t disconnect it from the negative battery connector and chassis). If it shows more then 1 Ohm: time to replace the wires and/or connectors and/or the relay! If everything is still fine connect the light-blue wire back into the Molex connector (make sure it’s really in there!), connect the batteries and you are ready to go.

As a new relay + wires + connectors is not more then $10 it may be worth to replace the circuit no matter what you measured. A new regulator/rectifier costs a LOT more!

Contributed by Jürgen Schöpf