Paddy_SP Posted November 11, 2022 Share Posted November 11, 2022 Back along I fitted a two-wire alternator as my mate had a brand new one that he let me have super-cheap (since my rebuild was swallowing every penny I had). I'm now at the point where I want to finish the wiring. The 'thick' terminal is clearly the main battery feed, while the 'thin' one is obviously for the indicator lamp. When I run the engine, the indicator wire shows around 6 volts at tick-over, so as the battery charge symbol on the Td5 dash is a 'negative on', the symbol stays off when the engine isn't running, and comes on when it is. I've tried wiring a separate 12v bulb with the indicator lamp wire connected to one side and +12 volts on the other, but once again, this only comes on when the engine is running. It appears to be charging OK, as the voltage goes up when I rev the engine. So my question is whether anyone here knows a way I can get the charge light working? Quote Link to comment Share on other sites More sharing options...
Peaklander Posted November 11, 2022 Share Posted November 11, 2022 I use a 97MY diagram for my 300TDi, knowing that it's really for the early TD5 and there, the charge light has +12V on one side and the alternator is on the other. In this way the lamp is on when the alternator isn't 'excited' and when it is, it matches the 12V from the other side and so the lamp goes out. The circuit is a little more complex as there's a resistor across the warning lamp, so that even if the lamp is missing, the alternator still gets the excitation voltage - which is what the warning circuit is really for. The alternator gets it's 0V reference from its body fastening but I presume this is OK as you say it is working. Maybe there is an earth missing at the dash display? The white core is +12V from IGN Quote Link to comment Share on other sites More sharing options...
Paddy_SP Posted November 11, 2022 Author Share Posted November 11, 2022 Thanks for your thoughts - I'll try implementing the circuit as shown; any idea where the resistor and diode live on a 300Tdi (if they're in the clocks I can steal them from a spare set I have!)? My instrument pack has a very good earth, by the way! Quote Link to comment Share on other sites More sharing options...
western Posted November 11, 2022 Share Posted November 11, 2022 The charge light resistor is buried in the main/dash loom, its not easy to get access. Quote Link to comment Share on other sites More sharing options...
Paddy_SP Posted November 11, 2022 Author Share Posted November 11, 2022 As I have a stripped-out 300Tdi loom - albeit from a Disco, that shouldn't be a problem! Is it easy to recognise? Quote Link to comment Share on other sites More sharing options...
Peaklander Posted November 12, 2022 Share Posted November 12, 2022 The resistor is only needed if the warning lamp isn’t functioning. It won’t fix the problem you have. Quote Link to comment Share on other sites More sharing options...
western Posted November 12, 2022 Share Posted November 12, 2022 9 hours ago, Paddy_SP said: As I have a stripped-out 300Tdi loom - albeit from a Disco, that shouldn't be a problem! Is it easy to recognise? On 110 loom it's looks like a in line glass fuse holder covered with a black soft plastic sleeve. Quote Link to comment Share on other sites More sharing options...
Paddy_SP Posted November 12, 2022 Author Share Posted November 12, 2022 3 hours ago, western said: On 110 loom it's looks like a in line glass fuse holder covered with a black soft plastic sleeve. Thank you! 1 Quote Link to comment Share on other sites More sharing options...
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