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Post by on Apr 22, 2024 21:01:57 GMT
The light cruiser has two engines each of which have A127 alternators.
One of the alts doesn't work the other was working but stopped working and both the ind light and the oil pressure light illuminated even with the key switched off.
No oil problem.
There was also a parasitic drain.
I am not that concerned as I have the godlike LTO batteries which would start a Diesel truck in a blizzard but it is slightly interesting to consider the reason for both of the lamps being illuminated. I think its a diode.
The parasitic drain was really bad. I was shocked.
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Post by Telemachus on Apr 22, 2024 21:49:10 GMT
The light cruiser has two engines each of which have A127 alternators. One of the alts doesn't work the other was working but stopped working and both the ind light and the oil pressure light illuminated even with the key switched off. No oil problem. There was also a parasitic drain. I am not that concerned as I have the godlike LTO batteries which would start a Diesel truck in a blizzard but it is slightly interesting to consider the reason for both of the lamps being illuminated. I think its a diode. The parasitic drain was really bad. I was shocked. Yes I would say a diode, that is allowing battery+ into the stator which then, via the field diodes, finds its way to the D+ terminal. Then back via the alternator warning light to the isolated panel +12v supply (ie the circuitry the non-battery side of the ignition switch) which is thus powering the oil light, the other end of which is connected to ground via the oil pressure switch. With the bulbs in series I’d expect them to be rather dim, but none the less visible. Doesn’t explain how the lights would be on with the engine running though - but perhaps you only noticed after you’d stopped the engine? |
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Post by on Apr 23, 2024 5:05:43 GMT
The lights are on when the engine is not running but I was intrigued that they are on even when the key is out of the ignition switch. They are dimly lit not bright.
I guess its time to get a new rectifier.
As for the LTO batteries these are used as jumper packs and are not the reason for the failed alternator. Well its possible but I think its just age.
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Post by tonyb on Apr 23, 2024 7:25:41 GMT
What Tellemachus says. Current flows, via a shorted diode, back up the warning lamp cable to the ign. on terminal on the ignition switch. That terminal also acts as a bus bar (joint) to feed both tee warning lamps and any gauges. They are all in parallel, so the resistance in the new negative path is very low because of the multiple paths.
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Post by on Apr 23, 2024 13:28:33 GMT
In fact maybe it was thr LTO which blew the rectifier. They suck like an ethiopian prostitute and the alternator was probably tired anyway. So yeah.
Rotating electrics arrr very tedious.
I suppose if I do replace alternators or parts I should just use the AGM starter battery or it will fry again.
The way to use the LTO may be to dump its capacity into the AGM as a sort of portable generator. 15v with virtually no sag under load makes for a great cranking experience but could be detrimental for the heater plugs I suppose. Maybe not ideal.
One of the 40Ah@15v blocks can happily chuck out 250 amps for cranking without dropping below 14.8v.
Mad shit but could be dodgy.
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