Club 80-90 Forums

Hi guys,

I recently replaced my dash ribbon with the excellent kit that Chris sells on here.

I have noticed I have a faint glow from my oil pressure light despite having excellent pressure (gauges showing 4.5 bar running).

Any info on how I can test the wiring and sender?

Thanks

Hmm - I need to get to the bottom of this. Similar issue here.

I suspect that the red LEDs I'm supplying are just far more sensitive than the originals, and that they glow due to a very low residual current in that circuit. My own dash did the same with my prototype board, but a bigger resistor in the circuit (as currently supplied) fixed it for me. Maybe it needs a still bigger resistor.

It would be good if someone with better electronics knowledge than me could explain why there might be a residual current when one side of the LED is at ignition voltage, and the other is at whatever voltage the blue exciter wire puts out (which I assumed would be the same as ignition voltage). There is a diode after the LED, which perhaps creates a potential difference - is that enough to create this small current?

Here's the schematic for the battery light.



If the IGNITION and ALTERNATOR are at the same potential, the light should go out.

Could the greater resistance in the alternator exciter wire cause enough of a potential difference to create a tiny current?
Could relays connected to the exciter wire (fridge, split charge) provide a route to earth?
Could the diode D1 have something to do with it?

Whatever the cause, I guess that reducing the current with an even bigger R4 would solve the problem. The LED is plenty bright enough with the supplied 3k9.

@bmouthboyo - I guess I should double check that you did fit the 3k9 in position R4.

CJH wrote:Here's the schematic for the battery light.



If the IGNITION and ALTERNATOR are at the same potential, the light should go out.

Could the greater resistance in the alternator exciter wire cause enough of a potential difference to create a tiny current?
Could relays connected to the exciter wire (fridge, split charge) provide a route to earth?
Could the diode D1 have something to do with it?

Whatever the cause, I guess that reducing the current with an even bigger R4 would solve the problem. The LED is plenty bright enough with the supplied 3k9.

@bmouthboyo - I guess I should double check that you did fit the 3k9 in position R4.

Not sure if this is relevant when mine is the oil pressure light that is slightly lit, not the battery light?

Do you have the schematic for the oil pressure light? I assumed it is a simple circuit that is earthed via the sensor in engine head and is cut when pressurised?