Re: '48 Electrical System Polarity

Posted by HH56 On 2011/3/6 15:09:06

The relay (or solenoid) is just an electromagnet attracting a piece of iron so doesn't care about polarity in this application. If it were trying to attract another magnet or electromagnet then yes, polarity would make a difference.

To prevent the machine gunning which I recommend you not allow, you need 3 and 4 on the solenoid both at the same time.

When you ground term 5, relay one comes in and applies power from term 1 and out to 4 for the pull in coil. At the same time powers indicator lamp and feeds the coil of relay 2 which is in series with solenoid hold in coil. That hold in voltage goes out terminal 3 to solenoid. Once solenoid pulls in, its internal contacts open the pull in coil and just leaving the hold coil in operation.

One set of remaining contacts in solenoid (term 7) extinguish the indicator lamp when solenoid is pulled in and the other set (term 6) closes and is the starting point for a series of contacts for the ignition cut out. It stays in this state as long as you are in OD.

When you kick down, relay 1 drops out killing voltage to everything, and closes its second set of points which are in the ign cut out circuit (terms 2 & 6). That circuit is now complete so coil is shorted. Engine misses a beat or two and solenoid drops out when torque is released opening the ign cut out points there. If for some reason those fail to open, relay 2 has a slight lag but does open. One or the other contacts either solenoid or relay will open quickly enough to keep the engine from dying. All this happens in a few milliseconds.