Output diode

[overyonder]

I have a 1977 ford 4600 tractor, diesel. My concern is a output diode located in a 10 gauge wire between the alternator and the solenoid.The system is externally regulated. Does a reading of 00 in both direction mean the diode is defective and if so will this cause the system warning light to glow? I have current on both wires at the warning light but I'm trying to find something to wire in to replace the socket and bulb itself. Nothing there at the moment.I been through all the harness according to wiring diagram and all seems to me okay except my doubt about the before mention diode?

 

[Slowpoke Slim]

If you have the diode loose in your hand, reading it with an ohm meter, one direction you will see a short, and switching the leads to the other polarity, you will see a resistance value. If you see an open in both directions, it's bad.

You have to have the diode out of the circuit. If it's in the circuit, the meter could be reading a ground path through the wiring harness, or to something else, throwing off your reading.

 

[Roadworthy]

Slim is entirely correct but I will add that when you replace the diode it must be installed in the correct orientation to work properly.

 

[Slowpoke Slim]

Good note Road,

I should have included that. A diode is like a one way valve, (only for electrical instead of water or hydraulics). It should be clearly marked (hopefully) as to it's polarity, so you can keep it straight when you take it out and put it back.

 

[BravoXray]

Even when forward biased, the diode should show some resistance, as it will drop about 0.6 volts when conducting.