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  1. Firstly Sorry for long post but need to give all the info as it may also help someone diagnose my problem I have 2 Lucas A127 65 amp alternators which are from my land rover defender tdi(200) to give a quick summary: one of these actual alternators has been on the car for last 6 years and has been charging both my batteries in the car (I have a National Luna dual battery split charge system installed) The alternator has been giving a good charge everyday of 14.2volts approx,although it would not hold that voltage steady when i put a bit of load on with lights heater it could go down to maybe 13,8volts which i realised is a bit weak. I have a Madman monitoring system in the car which give instant live time display of coolant temp,oil temps ,exhaust gas temp, oil pressure etc BUT more importantly with connection to this matter ,battery voltage so i can accurately see the battery charging voltage all the time and all these parameters are alarmed with low and high settings. Last week i had to replace a power steering pump / alternator mounting bracket which was easy BUT after putting it all back together i cannot get a charge on the alternator its sticking at 12.6 volts with a fully charged battery. As i say i never had ANY problems with charging at 14.2 volts before this current bit of work and would start vehicle on the button all day long even on coldest days Battery is fairly new 5 months ago( last one lasting over 9 years-showing vehicle has been keeping a good charge). I have checked the wiring to the alternator which is only 2 wires ,the main battery positve wire goes to the B+ post, and warning light cable to the D+ post of the alternator. After not getting a charge I have done a voltage drop test on the alternator positive lead and it came back good at @0.2 v same with the negative connection from the alternator casing to the negative post on the battery. Thinking i must have damaged the alternator somehow i took it out and did the following (stripped down )tests. on this alternator AND the spare one that i had lying about as a spare . 1) test on the rotor windings from the earth of the claw magnet of the rotor to each slip ring and both ended up open circuit (OL). Also the slip rings are in good condition no obvious wear. next tested the resistance between the slip rings and it came back as 3.1 ohms .my workshop manual gives a value of 3.2ohms As far as i can see this all in spec??? 2) Next the stator windings (which had the rectifier(s) unsoldered and removed ) testing between each pair of the 3 windings i got values of 0.2 ohms on each of the 3 pairs. .my workshop manual gives a value of 0.15ohms test on the stator windings from the earth of the magnet of the stator to each of the pair of 3 phase windings and all ended up open circuit (OL). As far as I can see this all in spec??? 3) rectifier:I tested on the diode setting from B+ post to the 3 top diodes and they all came back open circuit(OL) then swaped leads arounfd and tested the same 3 diodes and had readings of 0.54 volts(+/- 0.01volts) Then used the bottom earth point on the rectifier to check the other diodes and the all came with rhe same results. I even had a spare 3rd rectifier that i tested also with same results I cant be 100% on my testing at the correct points on these diodes as i have tried to reasearch where they are it comes back that there are 9 diodes 6 from the stator windings and 3 which come from the rotor windings. I will put some pictures of where i am testing these below. Lastly could not test the voltage regulator so replaced with new one (twice !,once on each alternator) and still the alternator when fitted to car produces no charge and charge lite constantly lit.Had the 2nd alternator (which gave allexactly the same readings as first) bench tested and is showing no charge with charge light constantly lit. I am completely stumped why for a start has the alternator come to give problems ONLY after removing its mounting bracket for repair . How sturdy are they? Is it usual to be easily damaged inside by slight knocking about whilst working around them? Remember the 2nd alternator( identical results) has been BENCH tested and also shows no charge. Am i testing all the diodes (and correctly)? I only see 6 of them but what is that black rectangular component with letters "DIET" on and could this also be a diode Just to say this is me wanting to understand what is wrong rather than just bung in a new rectifier /regulator or complete alternator. Im in South Africa and often drive long distances without any support or backup so need things working or at the very least to understand how to diagnose and fix
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