Series 2 1970, Series IIA 88, Charging Mystery

rob1miles said:

Family of 5 in a SWB for 9 months and 16000 miles, so perhaps you be wondering what to do with all the space?

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Hi rob1miles,

Coincidentally, I have 4 children! So it's a similar situation. I liked the bit about them meeting people, who helped them fix it every day! I think that's one of the benefits of an old Land Rover, you will meet people in remote areas who have a lot of knowledge, and are used to fixing things a thousand miles from the nearest Land Rover dealer!

ExMil109 said:

Hi OldV8,
When I first looked at this circuit, I also wondered why they didn't just connect the field to the switched ignition feed. I think the reason is that any voltage drop through the ignition switch would then be seen by the regulator as a low output voltage and it would increase the alternator output, maybe overcharging the battery. Hence the relay to give as direct a path as possible to the regulator.
I guess it depends how far you want to keep it original (and it does appear to be a rare setup). And of course you want it to be reliable during your 3-month trip!

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A further development: F+ve turns out to be permanently live! Hadn't even thought of that possibility until now, but wondered why the alternator would charge with the regulator bypassed. Still trying to get my head round what they did in Solihull!

Hi Exmil109 & rob1miles,

What are your views on the attached revised diagram? My thinking is that if the F+ve lead is connected permanently to the battery within the loom, then the relay must be about switching F-ve on and off?

Hmm. The reg + will be live all the time, is that the way yours is wired? Would that the wire that bypasses the ign switch? Would this allow the reg to drain the battery slowly between reg + and earth even when reg F is isolated by the realy? I honestly don't know, the limit of my understanding on this passed by a while back!
My other thought is, can you rectify the orgnal fault by making a like for like replacment and connecting it all up the way it was on the basis that it worked before? Its a bit of cop out but it could work. You could then take some meansurments and work out what is going on.

rob1miles said:

Hmm. The reg + will be live all the time, is that the way yours is wired? Would that the wire that bypasses the ign switch? Would this allow the reg to drain the battery slowly between reg + and earth even when reg F is isolated by the realy? I honestly don't know, the limit of my understanding on this passed by a while back!
My other thought is, can you rectify the orgnal fault by making a like for like replacment and connecting it all up the way it was on the basis that it worked before? Its a bit of cop out but it could work. You could then take some meansurments and work out what is going on.

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Hi rob1miles,

All good thoughts. Thanks.
The detailed description you sent suggests that the regulator only makes a connection to earth when it senses the voltage is over 14.4v - that's how it temporarily stops the alternator producing electricity, by shorting regulator + to earth, and breaking the field coil circuit. So I don't think having the regulator + live all the time, would be an issue.
Good idea to wire it as the old one was, although there are no markings on the old regulator unfortunately, which makes distinguishing between + and F difficult (and getting the polarity wrong apparently blows up the transistor type of regulator!). Still a good idea to try, and to understand how it was working. I am getting a spare 4TR regulator, if the worse comes to the worst!

OldV8 said:

Hi rob1miles,

All good thoughts. Thanks.
The detailed description you sent suggests that the regulator only makes a connection to earth when it senses the voltage is over 14.4v - that's how it temporarily stops the alternator producing electricity, by shorting regulator + to earth, and breaking the field coil circuit. So I don't think having the regulator + live all the time, would be an issue.
Good idea to wire it as the old one was, although there are no markings on the old regulator unfortunately, which makes distinguishing between + and F difficult (and getting the polarity wrong apparently blows up the transistor type of regulator!). Still a good idea to try, and to understand how it was working. I am getting a spare 4TR regulator, if the worse comes to the worst!

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Hi,
Your last post got me thinking (so many thanks!). The attached is an alternative I think? Also there was a definitely a connection from C2 on the relay to the old regulator, and F-ve from the field coil also went to the regulator. This could be it!

Still a mystery!

Have tried both of the latest alternative wiring schemes. Only charges when the regulator is bypassed (and then of course, after a while, too much, because it is not regulated).

I am persevering with the last wiring diagram. I think Solihull would have been less likely to suddenly start switching off the -ve. Too unconventional given they switch off the +ve in all other diagrams.

There is a bit over 12v to C1 with the ignition off, and then to Regulator +ve via the relay when the ignition is turned on. So that seems to be working.

BUT it doesn't charge when running.

ONLY charges when the regulator is bypassed (F+ve and F-ve leads are connected, either by the relay or directly)! (Thus it appears the alternator is working OK).

Any thoughts welcome!

Hi Old V8,
With your first circuit, as Rob said, there will be a small current into the regulator when the ignition is off. Not a big problem, but may drain the battery over a long period. The second circuit should work, but doesn't improve on the "standard" circuit from the manual.
If you have 12V into + on the regulator and into F+ on the alternator and it's not charging then I'd suspect the regulator is faulty. You can confirm by connecting F- on the alternator to ground, bypassing the regulator and running the alternator flat out. If that gives a good +14V charge then the alt is good and the regulator is faulty. Worth checking that the regulator has a good earth though - if it isn't well-earthed, it can't drive the field on the alternator properly.

Hi ExMil109,

Thanks, that's a useful tip.

There has been a major discovery. Which is that (presumably by whoever put in the 1970s Japanese replacement regulator) the F+ve lead had been earthed where it came out of the loom near the relay! It looked orignal, so I assumed that was meant to be there. Mindboggling really, but I guess the polarity in the regulator wasn't important, and it doesn't matter which way the current flows round the field coil? Still trying to work out how the permanent +ve lead was connected to F+ve!

I have rewired it all now in the standard way (as attached below). Although no 3AW in my case, of course.

It is not charging, but the earlier trials may have blown the 4TR. I am waiting for another to turn up.

I tried putting F-ve to ground and it does charge, as per your tip. 16v across the battery, and 33.5A from the alternator output.

Thanks again for your help.

Hi OldV8,
Well, it sounds like your alternator is healthy! Hopefully a new regulator will get it charging properly.
I don't think it makes a significant difference if the alt field is connected "backwards" - it will still create a magnetic field and the alternator will produce current. With a dynamo it would reverse the polarity, but an alternator always produces the same polarity because of the rectifiers.
That said, there will be some residual magnetic field so probably best to connect it as the manufacturer intended...

have you fitted the 3AW unit controlling the ignition warning light https://forums.jag-lovers.com/t/ignition-light-question/368634

ExMil109 said:

Hi OldV8,
Well, it sounds like your alternator is healthy! Hopefully a new regulator will get it charging properly.
I don't think it makes a significant difference if the alt field is connected "backwards" - it will still create a magnetic field and the alternator will produce current. With a dynamo it would reverse the polarity, but an alternator always produces the same polarity because of the rectifiers.
That said, there will be some residual magnetic field so probably best to connect it as the manufacturer intended...

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Hi Exmil109,

Good and bad news. It worked for a short while with the new 4TR - 14.4v across the battery. Then the regulator got warmish, there was even a slight electrical burning smell. Now 16.5v across the battery!

I have re-checked all the wiring. Is it possible that the 4TR wasn't good?

It is a modern replacement one.

https://www.autoelectricsupplies.co.uk/product/705

mystery said:

have you fitted the 3AW unit controlling the ignition warning light https://forums.jag-lovers.com/t/ignition-light-question/368634View attachment 200538

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Hi mystery,

Good diagram of the whole charging circuit, including the inside of the regulator!

Just checking whether you meant the charge indicator light, or the light that comes on when you turn on the ignition and goes out when the engine starts? Different things in my case.

Please see earlier in the post about the charge indicator light. I have a rare voltmeter instead, which shows off charge/on charge. There is no 3AW as far as I can see, and there is certainly no connection to AL on the alternator.

Can you get the top off and look inside? Zenners get hot but this sounds more like over current. That could be low resistance in the field windings or a short? Remind me is your set up neg earth?

rob1miles said:

Can you get the top off and look inside? Zenners get hot but this sounds more like over current. That could be low resistance in the field windings or a short? Remind me is your set up neg earth?

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Hi rob1miles,

It looks prety sealed. Possibly drilling the rivets out would make it possible to prise the back plate off (it looks a very tight fit, and there is also a rivet in the centre of the backplate too). I don't think it was intended to be accessible!

I checked the resistance between the slip rings when I had the alternator apart, it was just over 3 Ohms. Autobooks said it should be 3.8 Ohms.
I didn't do their test beween the outer slip ring and rotor pole, because I didn't have a 110v supply and a 15W bulb! But my multimeter said resistance was infinite, so I thought that was OK?

A short somewhere else in the system is possible of course. Any thoughts?

I'm clutching at straws!

Hi rob1miles,
Thanks for trying! It is very trying!
I think these modern 4TRs are PCB, so it's shot. I will have to get another one in any case. Fingers crossed (or perhaps a revelation will happen in the meantime)!

am I correct in that you say the warning light as been replaced with a volt meter ,yet the warning light is the mean that the alternator get it excitation ,on later models a diode and 100 ohm resistor fitted so if bulb failed alternator would still charge
I take it you did look at link posted

In case the detail is of any help:

F is connected to -ve permanently now in the blown 4TR. The system is charging (overcharging - 16.5V).

Current flowing in the field coil is 3A.

mystery said:

am I correct in that you say the warning light as been replaced with a volt meter ,yet the warning light is the mean that the alternator get it excitation ,on later models a diode and 100 ohm resistor fitted so if bulb failed alternator would still charge
I take it you did look at link posted

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Hi mystery,

I did take a look, thanks.

They seem to have a different issue? Ignition/charge light coming on.

My ignition light is OK. Nice and bright when you turn the ignition on, then goes out straight away when the engine starts. Also my system is charging - it's just charging too much!

My understanding is that (if you have one) the 3AW masures the AC voltage at AL and if it is above 7.5v it puts the charge warning light out. Doesn't have any effect on the exciting of the alternator.

Voltmeter is original Land Rover. Photo again for you.