Diode Resistance

[nelmo]

I'm having a problem with my motorbike not starting. The troubleshooting guide in the service manual asks me to check continuity on the neutral diode, saying there should be a 'small resistance' between the terminals, with the diode out of the circuit (no voltage).

 

I've measured 750 ohms - is that considered 'small' or is it broken?

[fry61]

Diode resistance should be near zero when connected correctly so your's is reading high & very little current will flow through it.

[nelmo]

OK, many thanks...

[sj-bradley]

Are you testing using the "diode" setting on your meter?

 

If so, that could be reading the 0.75 volt drop that is normal for a diode. A diode acts like an open circuit when the wrong way round in your circuit and a short circuit when the right way round. If you place a low watt lamp and diode in a series circuit from your battery, most of the battery voltage will appear across the lamp with a small 0.7 volt drop across the diode.

 

Hope that helps? (It's late and I should be in bed !)

 

Simon.

[nelmo]

I was measuring resistance, not voltage. Turns out that 750 ohms was fine (according to Honda mechanic at the dealer). I put the diode back in, wiggled a few more connectors and suddenly it fired up - must have been a dodgy connection somewhere...

[Guest peter2b2002]

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peter2b