11 AC Lucus Alternator

Tom W

Active Member
#41
My Jag has the same alternator. The 6RA relay went bad, despite (or because of) being a new replacement. It was arcing and causing the alternator to overcharge. I replaced it with a modern relay as they’re much cheaper, and so far much more reliable. The 6RA isn’t particularly waterproof, and mine was a bit corroded inside when I took it apart. You could try a modern substitute to see if that cures the problem.
 
#42
My Jag has the same alternator. The 6RA relay went bad, despite (or because of) being a new replacement. It was arcing and causing the alternator to overcharge. I replaced it with a modern relay as they’re much cheaper, and so far much more reliable. The 6RA isn’t particularly waterproof, and mine was a bit corroded inside when I took it apart. You could try a modern substitute to see if that cures the problem.
I did try swapping in a modern relay, but for some reason the car didn't like it.... Maybe it was the wrong type or wrong wiring. Just another thought - I wonder if I have a short in the ignition causing the relay to latch. I think the modern relay did fire straight away, which would mean a short in the ignition, right? Will have to do more testing! Cheers :)
 

Tom W

Active Member
#43
I think I just used a 4 pin, normally open relay. Nothing complex, it came off the shelf at the local motor factors. The relay should only be energised if the ignition is switched on. If the feed from the ignition switch to the relay is live all the time, then you’ve got some investigation to do.
 

cobraboy

Well-Known Member
#44
Not all modern relays have the spades in the same locations, some are reversed. It is best to get a magnifying glass and check out the numbers next to the spades and connect to suit that way rather than just assuming they are all the same.
 
#46
Not all modern relays have the spades in the same locations, some are reversed. It is best to get a magnifying glass and check out the numbers next to the spades and connect to suit that way rather than just assuming they are all the same.
Yes I thought I had done it 'by the numbers'. Interestingly when I put a multimeter on the RA I can't find any current causing it to latch...
PS I really appreciate everyones help - the missus is impressed with you lot too!
 

sdibbers

Well-Known Member
#47
Yes I thought I had done it 'by the numbers'. Interestingly when I put a multimeter on the RA I can't find any current causing it to latch...
PS I really appreciate everyones help - the missus is impressed with you lot too!
Rob, you can use a multi tester to check what each connection is. The coil should have some continuity (some resistance, not completely cut off). Find the two connectors for that and the other two should be your contact spades. If you find that the two contact spades have zero ohms I would say you have a normally closed relay (rare, but not unheard of) and it won't be suitable for your needs.
 
#51
Yeah that's what I had.... Hmm. I'm starting to think I have a short in the relay trigger wire (W1) somewhere....I recently installed a new ignition - I wonder if there's a leak in there that is giving the 6RA just enough to latch on and drain....but then why would the relay sometimes not fire, resulting in no charge?? More investigation required. It's funny because sometimes it's perfect - sometimes not. Something else that's interesting is my mulitimeter.....I'm new to them. Now when I'm measuring amperage it doesn't give a reading straight away but starts and 0 and increases to the reading....when I take the terminals off the reading also leaks away until 0....and sometimes even stays at .3 or so when not touching anything. I wonder if my meter is bung....?
 

sdibbers

Well-Known Member
#52
Yeah that's what I had.... Hmm. I'm starting to think I have a short in the relay trigger wire (W1) somewhere....I recently installed a new ignition - I wonder if there's a leak in there that is giving the 6RA just enough to latch on and drain....but then why would the relay sometimes not fire, resulting in no charge?? More investigation required. It's funny because sometimes it's perfect - sometimes not. Something else that's interesting is my mulitimeter.....I'm new to them. Now when I'm measuring amperage it doesn't give a reading straight away but starts and 0 and increases to the reading....when I take the terminals off the reading also leaks away until 0....and sometimes even stays at .3 or so when not touching anything. I wonder if my meter is bung....?
Are you reading a voltage at W1 with the ignition switched off?
 
#53
Ignition off, no voltage at W1, W2 or C2. 12v+ at C1, on the battery post of the alternator and on both F+ and B on the alternator - no voltage on the upper tang which normally gives 6v when running (W?). 12v+ at both terminals of the regulator. It has to be coming through the ignition switch, right? I must have something touching or the wiring wrong....or a fault in it. Maybe I should go to individual switches for coil/pump/alt racing style....
 
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