Dashboard electronics query
Discussion
I have just fitted a new dash to the Grif at the same time I have had a new loom to the engine bay - bit daft really as now I have a few electrical problems and don't know if its the loom or dash, hey ho.
Anyway, on the dash I have a battery warning light and also a warning light incorporated in the speedo. When I turn ignition on the light in the speedo illuminates as you would expect however the dash warning light does not. However when the car is running and I turn off ignition both lights illuminate as the engine dies which is normal. So there must be two different feeds - any ideas why and why the lights both illuminate on power down but not on power up. Also presumably one feed is from the alternator, where would the other feed come from??
Any pointers welcome!!
Ian
edited to add if I switch the polarity on the warning light both come on with ignition and go off on start up but only the light in the speedo comes on when I power down so I am guessing this is the better of both options!
Anyway, on the dash I have a battery warning light and also a warning light incorporated in the speedo. When I turn ignition on the light in the speedo illuminates as you would expect however the dash warning light does not. However when the car is running and I turn off ignition both lights illuminate as the engine dies which is normal. So there must be two different feeds - any ideas why and why the lights both illuminate on power down but not on power up. Also presumably one feed is from the alternator, where would the other feed come from??
Any pointers welcome!!
Ian
edited to add if I switch the polarity on the warning light both come on with ignition and go off on start up but only the light in the speedo comes on when I power down so I am guessing this is the better of both options!
Edited by roseytvr on Tuesday 28th May 17:04
roseytvr said:
I have just fitted a new dash to the Grif at the same time I have had a new loom to the engine bay - bit daft really as now I have a few electrical problems and don't know if its the loom or dash, hey ho.
Anyway, on the dash I have a battery warning light and also a warning light incorporated in the speedo. When I turn ignition on the light in the speedo illuminates as you would expect however the dash warning light does not. However when the car is running and I turn off ignition both lights illuminate as the engine dies which is normal. So there must be two different feeds - any ideas why and why the lights both illuminate on power down but not on power up. Also presumably one feed is from the alternator, where would the other feed come from??
Any pointers welcome!!
Ian
edited to add if I switch the polarity on the warning light both come on with ignition and go off on start up but only the light in the speedo comes on when I power down so I am guessing this is the better of both options!
I would think the second way you have it is correct. The dash one is an led, so polarity sensitive but the one in the speedo is a normal bulb. Think about the way a "normal" charge warning light works, +12v supply and then earthed through the alternator regulator. As the alternator output rises when running, a voltage is applied to the other side of the bulb, what was originally earthed, hence the bulb gradually dims out rather than being on or off. When you power down the voltage from the alternator gradually falls but what was the ignition supply side is now earthed through other circuits, hence the light coming on then dimming out. The led in the dash shouldnt do this. Substitute the led for a small bulb and try it.Anyway, on the dash I have a battery warning light and also a warning light incorporated in the speedo. When I turn ignition on the light in the speedo illuminates as you would expect however the dash warning light does not. However when the car is running and I turn off ignition both lights illuminate as the engine dies which is normal. So there must be two different feeds - any ideas why and why the lights both illuminate on power down but not on power up. Also presumably one feed is from the alternator, where would the other feed come from??
Any pointers welcome!!
Ian
edited to add if I switch the polarity on the warning light both come on with ignition and go off on start up but only the light in the speedo comes on when I power down so I am guessing this is the better of both options!
Edited by roseytvr on Tuesday 28th May 17:04
I know what I mean even if my explanation is crap 
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