My latest toy.

Tom W

Active Member
#61
Which alternator do you have? The battery sensed alternator I described is the later type. Lucas 18ACR or similar, that’s internally regulated. Or do you have a Lucas 11AC? That is externally regulated with a 4TR regulator, and has a 3aw module to operate the light and a 6RA relay relay to disconnect the alternator when the ignition is off. The round can could be a 3aw module. The systems are wired differently.
 
#62
There is no make on it Tom, it appears new and is similar to ones available on eBay. I have a 3aw fitted, I think its the round can in the driver's side, can I do away with this and feed the warning light direct. I suspect the 3aw is faulty.
 

Tom W

Active Member
#63
Have you got a photo of your alternator? Sometimes 11acs get replaced with later alternators but the now redundant relays get left in place. Or the round can could be the flasher for hazard warning lights, and nothing to do with the alternator. If you have an 11ac alternator, you need the 3aw. Best we work out what you’ve got , before trying to diagnose the problem further.
 
#64
Have you got a photo of your alternator? Sometimes 11acs get replaced with later alternators but the now redundant relays get left in place. Or the round can could be the flasher for hazard warning lights, and nothing to do with the alternator. If you have an 11ac alternator, you need the 3aw. Best we work out what you’ve got , before trying to diagnose the problem further.
Thanks for helping me Tom, I'll try and upload photos, but I have had a problem with the files being too big. The can isn't anything to do with the flashers or indicators. I unplugged a wire it didn't affect either.
I have had a thought, if the alternator is being activated by a feed to the small terminal, but continues feeding when the ignition off. I could rig an ignition controlled feed so it is off when the engine is off. The alternator is being activated by the permanent small brown wire but this is on all the time. I won't have a warning light, but I can live with that.
 
#65
Thanks for helping me Tom, I'll try and upload photos, but I have had a problem with the files being too big. The can isn't anything to do with the flashers or indicators. I unplugged a wire it didn't affect either.
I have had a thought, if the alternator is being activated by a feed to the small terminal, but continues feeding when the ignition off. I could rig an ignition controlled feed so it is off when the engine is off. The alternator is being activated by the permanent small brown wire but this is on all the time. I won't have a warning light, but I can live with that.
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#66

Tom W

Active Member
#68
I could do with seeing the back of the alternator to identify what sort of wiring it needs. It doesn’t look like an 18ACR, they have a big plastic cover on the back. It doesn’t look like an original 11AC either. Im not sure what your car would have had originally, I don’t know when the V8 changed to an internally regulated alternator. From the photo, it looks like a slightly more modern internally regulated alternator. I have a similar looking one on a V8 Range Rover Classic.

You really need to work out what you’ve got. Do you have a wiring diagram? You’re likely to do some damage to something by speculatively connecting wires, or worse still, set something on fire.
 
#69
I could do with seeing the back of the alternator to identify what sort of wiring it needs. It doesn’t look like an 18ACR, they have a big plastic cover on the back. It doesn’t look like an original 11AC either. Im not sure what your car would have had originally, I don’t know when the V8 changed to an internally regulated alternator. From the photo, it looks like a slightly more modern internally regulated alternator. I have a similar looking one on a V8 Range Rover Classic.

You really need to work out what you’ve got. Do you have a wiring diagram? You’re likely to do some damage to something by speculatively connecting wires, or worse still, set something on fire.
Thanks Tom, I am still having problems loading photos. I am of the opinion that the alternator was damaged before I got it. I am also seriously considering getting a new one, doing the wiring as I understand it and mounting a discreet warning light. There is something about this set up I can’t figure out. The alternator fitted has what appears to be a diode pack on the back. It has the usual 3 connectors. 2 large ones and a small one. It also a larger bolt type connector B+ and a smaller one with W. there is also a separate small spade connector. I have converted dynamo to alternator set ups in the past without any problem. I can't get a seperate warning light to work from any of the connections

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Tom W

Active Member
#70
It looks as though your alternator is non standard. The W terminal isn’t needed. That’s for driving the tacho when the alternator is fitted to a diesel. If your alternator has the standard 3 wire Lucas style plug (I can’t see on your photo as it doesn’t show the wiring), the B+ terminal might be an additional 12v permanent live connection. What are the other terminals marked as? One should be marked IND. this is where the ignition feed via the bulb should go.
 
#71
It looks as though your alternator is non standard. The W terminal isn’t needed. That’s for driving the tacho when the alternator is fitted to a diesel. If your alternator has the standard 3 wire Lucas style plug (I can’t see on your photo as it doesn’t show the wiring), the B+ terminal might be an additional 12v permanent live connection. What are the other terminals marked as? One should be marked IND. this is where the ignition feed via the bulb should go.
something strange is going on inside this alternator, I rigged a bulb between the smallest of the 3 terminals and an ignition source. The light lit as expected I started the engine, it charged straight away and the bulb went to a small glow. But the engine wouldn't turn off until I disconnected the ignition feed. The alternator is activated by applying a voltage to the warning light terminal either directly or via a bulb, but the only way to stop it charging is by removing the warning light feed. I am puzzled why that should be. I could bodge a momentary switch to activate the alternator. This would have to be pressed every time the car is started, I don't really want to do that. I am still considering buying a new alternator and wire it up independent of the cars wiring.

The W terminal is under the rubber cap at the top.
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Tom W

Active Member
#72
Your alternator is newer than the car, but should be compatible with the original wiring.

I think you need to trouble shoot the wiring on the car, it’s not a complex circuit, and you should have enough for the alternator to work with just the 3 pin plug. The reason the car didn’t turn off is because the extra wiring you’ve added will have bypassed the ignition switch, either accidentally, or through some fault in the alternator. What wattage bulb did you use? It should go out completely, not go dim if everything is working right.

Checking the original wiring is straight forward. The two large wires go to the battery, via the ammeter shunt behind the dashboard. They should both have 12v permanently. Check this with a meter. The smaller wire shouldn’t be live with the ignition off. With the ignition on, this should also show a voltage, though maybe not 12v because of the bulb. With the ignition on, connect the small terminal to earth (be careful not to earth the big terminals, they’re not fused). The light on the dash should illuminate. If it doesn’t, then check the bulb, and check there’s power going into the bulb. Once the light is working, you should have everything you need to get the alternator to work, assuming you haven’t fried it by connecting the wrong wires to the wrong terminals.

The other terminals on the alternator aren’t necessary for your installation. The W is for a tacho on a diesel, the B+ is an alternative connection for the main battery feed, for cars with ring terminals on the wiring. The small spade terminal is for a suppression capacitor.
 
#73
Your alternator is newer than the car, but should be compatible with the original wiring.

I think you need to trouble shoot the wiring on the car, it’s not a complex circuit, and you should have enough for the alternator to work with just the 3 pin plug. The reason the car didn’t turn off is because the extra wiring you’ve added will have bypassed the ignition switch, either accidentally, or through some fault in the alternator. What wattage bulb did you use? It should go out completely, not go dim if everything is working right.

Checking the original wiring is straight forward. The two large wires go to the battery, via the ammeter shunt behind the dashboard. They should both have 12v permanently. Check this with a meter. The smaller wire shouldn’t be live with the ignition off. With the ignition on, this should also show a voltage, though maybe not 12v because of the bulb. With the ignition on, connect the small terminal to earth (be careful not to earth the big terminals, they’re not fused). The light on the dash should illuminate. If it doesn’t, then check the bulb, and check there’s power going into the bulb. Once the light is working, you should have everything you need to get the alternator to work, assuming you haven’t fried it by connecting the wrong wires to the wrong terminals.

The other terminals on the alternator aren’t necessary for your installation. The W is for a tacho on a diesel, the B+ is an alternative connection for the main battery feed, for cars with ring terminals on the wiring. The small spade terminal is for a suppression capacitor.

Thank you very much Tom, all you say makes sense and I understand it. I have tried different size bulbs, the first one was an indicator I think 21 watt, with this the engine wouldn't switch off. I substituted it with a smaller 3 watt bulb this still glowed the car charged but the engine turned off. The third one is a little dash indicator this glowed when the car was charging the engine turned off ok. I have ordered a new alternator a standard one I will wire it independently and have a little additional warning light. I know its not standard, but as you say there may be a fault in the wiring, and from experience it could be a nightmare to find. Thanks for all your help, I thought I was going insane at one stage.
 

Tom W

Active Member
#74
The wiring shouldn’t be complex to fix. You’re better off fixing the original wiring rather than adding more non-standard wiring and potential unreliability.

You say your car doesn’t have an ignition warning light, it should have. It is one of the 3 along the top row. Left hand one from memory, though I’m not near to my car to check. Check the bulb and the wiring for that, it’s the most likely cause for the alternator not working in the first place. The alternator probably got fried later by connecting the wrong wires to the wrong terminals.
 
#75
The wiring shouldn’t be complex to fix. You’re better off fixing the original wiring rather than adding more non-standard wiring and potential unreliability.

You say your car doesn’t have an ignition warning light, it should have. It is one of the 3 along the top row. Left hand one from memory, though I’m not near to my car to check. Check the bulb and the wiring for that, it’s the most likely cause for the alternator not working in the first place. The alternator probably got fried later by connecting the wrong wires to the wrong terminals.
Thanks Tom, the car came with a spare set of gauges, so my set up is a mix of the two. I now know where the ignition light is and I know the bulb is ok, what I meant was that I have never seen it illuminated it doesn't light with power applied to its wire. . I stupidly thought the oil warning light was the ignition one. I only realised the car wasn't charging when the battery went flat. I suspect the damage to the alternator was done before I got it although I accept I could have done it. I am a bit nervous about connecting a new alternator to dodgy wiring. I will carry out a full check of the present set up. Am I right in thinking I don't have a 3 aw thingy?
 

Tom W

Active Member
#76
There isn’t a 3aw on your car, that’s for cars with 11AC alternators.

How are you checking the bulb & wiring for the warning light? You don’t apply 12v to the wire where it connects to the alternator. It will have a 12v supply from the ignition, you need to earth the small wire on the alternator plug. Then turn the ignition on to the run position, but don’t start the car. If that doesn’t make the light illuminate, check if there is 12v at the bulb socket.

Do you have a wiring diagram? It makes everything much easier to understand.

If you’ve had the dash binnacle out, there’s a possibility you’ve dislodged a connection behind, it might be a simple fix.
 
#77
There isn’t a 3aw on your car, that’s for cars with 11AC alternators.

How are you checking the bulb & wiring for the warning light? You don’t apply 12v to the wire where it connects to the alternator. It will have a 12v supply from the ignition, you need to earth the small wire on the alternator plug. Then turn the ignition on to the run position, but don’t start the car. If that doesn’t make the light illuminate, check if there is 12v at the bulb socket.

Do you have a wiring diagram? It makes everything much easier to understand.

If you’ve had the dash binnacle out, there’s a possibility you’ve dislodged a connection behind, it might be a simple fix.[/QUOTE


Well Tom you are right, I took the front off the dash, checked the bulb which was ok. I got the bulb to light by connecting an earth with ignition on, I did a continuity check on the connection from the alternator which showed a fault.. I took the rest of the binnacle out and lo and behold the brown and black wire had come a drift from the multi plug. Easy fix, I have an ignition light although it still glows when the car is charging I am sure a change of alternator will fix that. Thanks for all your help and patience.
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roverp480

Active Member
#78
I wonder if there is something wrong with the alternator to vehicle wiring . You say the engine continues to run after you have switched off the ignition, when the warning light you have rigged up is connected. There cannot be enough current to feed the ignition circuit through the bulb, so it must be coming from somewhere else. The alternator is connected to the battery side of the ignition switch so it shouldn't be feeding from there with the ignition off. I would check out all the feed wires and ignition switch connections to make sure there is not a fault
 
#79
I wonder if there is something wrong with the alternator to vehicle wiring . You say the engine continues to run after you have switched off the ignition, when the warning light you have rigged up is connected. There cannot be enough current to feed the ignition circuit through the bulb, so it must be coming from somewhere else. The alternator is connected to the battery side of the ignition switch so it shouldn't be feeding from there with the ignition off. I would check out all the feed wires and ignition switch connections to make sure there is not a fault

I don't know how but it appears the alternator is putting out 12 volts through the terminal which connects the warning light. I have got it 90% right with the help of Tom W. It now operates ok but the warning light is still glowing slightly when the alternator is charging. I have a new correct alternator coming next week so fingers crossed.
 

Tom W

Active Member
#80
It should put 12v, or thereabouts out of the terminal the light connects to. That’s what turns the light off. When everything is working properly, the bulb has the same voltage to both terminals, so doesn’t illuminate. If there’s a mismatch e.g. low charging voltage, then the light will illuminate.
 
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