Weird alternator regulator problem

[cheesegas]

Hi all. Got a weird alternator issue, I'm pretty clued up on electrics but this is weird!

 

Setup is an Isuzu 3KC1 (idles at 1000rpm as per the engine manual), single alternator V belt drive (tensioned, no slipping), 75a Lucas A127 clone (negative field control) connected to the starter battery, three 110ah leisure bank, one 110ah starter, Sterling VSR set to 13.6v, Victron BMV on the leisure bank with start batt monitoring.

 

Originally there was a very old but functioning Sterling alternator regulator fitted. This worked great, slowly ramping up the voltage to 14.4v within 20 min of starting the engine. Charging a depleted bank resting at 12.2v, I'd see around 30a charge current for half an hour or so before tailing off as expected. However the regulator recently failed closed, meaning the voltage would rise up to over 15v within minutes of starting the engine, and then the regulator's relay would open when it trips on high voltage, leaving the alternator's internal regulator to work.

 

I removed the old Sterling and have been using the internal regulator for a while - on startup, I'd see 15-20a charge current at 13.6v, current decreasing as voltage increases as normal. However, putting a load of around 25a on the battery with the engine running and a charge current of 10a would instantly pull the voltage down, and a current of around 10a would flow from the batteries. Made me have doubts about the alternator's regulator.

 

Anyway, yesterday I finally got round to fitting a new Sterling Pro Reg D. Checked the ignition feed, replaced the 12v battery sense and all grounds to the Sterling, checked that I'm seeing 6-8v from the field wire on the alternator. Fitted the regulator and I'm seeing absolutely no change in the above behaviour! No error lights on the regulator and it's in high charge mode. It also does not ramp up the charge voltage at all; after 2hrs of engine running, the voltage is still the same as if the internal regulator is being used.

 

I've tried the below:

- Disconnecting the field wire from regulator to alternator does nothing at all, no change to voltage or charge current.  

- There's a 0.5a current flowing in the field wire. Sterling manual says this should be around 10a?

- All grounds have under 0.05v potential difference between them; alternator, both battery banks, sense wires for the Sterling (both battery and alternator ground sensing)

- All 12v points have under 0.05v difference between them; alternator, both battery banks, sense wire for the Sterling

- Sterling is set to negative field control

 

The new Sterling is currently connected. The batteries got quite low last night as I had the inverter on, 12.1v rested so they should be accepting a high charge current. Started the engine this morning and the charge current went up to 25a at 13.6v relatively quickly which is what I'd usually expect, then after less than a minute it dropped to 10a. When the fridge kicks in, charge current drops to 6a at 13.6v.

 

Is this is a stuffed alternator internal regulator? And a DOA Sterling? The Sterling appears to be doing precisely nothing, the white field wire is not sinking any significant current from the field winding even though the lights on the front say it's all happy.

 

Thanks for your help!

[Tracy D'arth]

"Field " wire?  10A? highly unlikely. To what are you referring as the field wire?

 

Check the sensing wire to the battery + is correct. A poor or open connection will cause the Sterling to go to high charge all the time.

 

The internal regulator in the alternator has to be in working order for the Sterling to work correctly.

 

Phone Charles at Sterling, he is helpful.

[Tony Brooks]

Initial thought. High resistance on the domestic battery charging circuit. Dirty battery terminal, faulty master switch, loose connection some where.

 

Some of the statements and numbers don't seem to make sense.

 

A Sterling or any other external regulator can't mess with voltages until the alternator's regulator starts to regulate unless the internal regulator has been totally disconnected.

 

3 x 110Ah batteries at around 12.2 volts gave me in excess of 80 amps at first start with a 70 amp alternator. Yours sounds low, have you got a/some faulty diodes?

 

 

[Sir Nibble]

First off, 13.6V is stupidly low, where are you measuring it? Agree with the 10A comment above,  whoever wrote that would have rejected every alternator I have seen in more than 40 years of rebuilding them. "Helpful" is not the word I would use for Sterling. 

[nicknorman]

My 175A Iskra takes 4.25A field current when the field wire is connected to 13v, so a 70A alt is never going to take 10A. Although interestingly a lot of alternator regulator chips boast being able to supply 12A or more field current - not sure what alternator could take that though!

 

Anyway, you mention the current in the field wire but not the voltage across it. With one end of the field at battery voltage and the other end at 0v you should get max alternator output (only try this if your batteries are at a fairly low SoC) so you could try forcing the field to max current and see what the charge current is. This would show whether there is an alternator issue or not.

 

Edit: oh and yes, do check the voltage on the back of the alternator (B+) is also the 13.6v you mention, when the alternator is operating, to eliminate the possibility of some severe voltage drop between alternator and battery, which of course would only manifest itself when current was flowing.

Edited November 5, 2021 by nicknorman

[frangar]

7 minutes ago, Sir Nibble said:

"Helpful" is not the word I would use for Sterling. 

Me neither!!...I have however found Adverc to be incredibly helpful both with Brian the original owner and the chaps that own it now....I find Sterling kit to be poorly designed and built...

[cheesegas]

5 minutes ago, Tracy D'arth said:

"Field " wire?  10A? highly unlikely. To what are you referring as the field wire?

 

Check the sensing wire to the battery + is correct. A poor or open connection will cause the Sterling to go to high charge all the time.

 

The internal regulator in the alternator has to be in working order for the Sterling to work correctly.

 

Phone Charles at Sterling, he is helpful.

Yep, that's my thoughts that the alternator regulator is dodgy. I replaced the entire alternator less than 6 months ago due to a bad bearing but it could still be bad. The field wire is what Sterling refer to as the 'field control wire' which comes from the regulator and is connected to one of the alternator brushes; in the case of my neg field control alternator, it should be sinking current into the regulator to raise the field voltage. Sense wires are all correct, I replaced it all with the new regulator just in case. I'm seeing no drop when measuring voltage between the battery and regulator sense wire. The 10a is quoted from the manual, it says it can be as high as 13a which I agree is high.

 

 

 

2 minutes ago, Tony Brooks said:

Initial thought. High resistance on the domestic battery charging circuit. Dirty battery terminal, faulty master switch, loose connection some where.

 

Some of the statements and numbers don't seem to make sense.

 

A Sterling or any other external regulator can't mess with voltages until the alternator's regulator starts to regulate unless the internal regulator has been totally disconnected.

 

3 x 110Ah batteries at around 12.2 volts gave me in excess of 80 amps at first start with a 70 amp alternator. Yours sounds low, have you got a/some faulty diodes?

Thanks. Confident that all connections are good and clean as I replaced it all when I fitted the VSR a few months ago. Isolator switches and battery terminal clamps are also brand new, and I'm not seeing any voltage drop across any components in the system. Measuring between battery positive post and any other point in the system doesn't show any voltage drop either. Agreed on the diodes, although why it initially charges at high current before immediately dropping has me stumped. I'm going to fit a new alternator regulator and diode pack I think. What doesn't make sense in my statements?

[Tracy D'arth]

Have you also checked the negatives?

[nicknorman]

Just thinking aloud, the field current is low. Field current is generated by the field diodes (assuming 9 diode machine), passes through the brush, rotor winding (which is a resistive load), brush,  regulator, to 0v. So presumably, with low side regulation if you connect the “field wire”, which I presume connects to the second brush, to 0v with the alternator running, you should get 4A or so field current and max output. If you get much less than 4A and not 70A or so generated, maybe one or more field diodes is blown?

 

Oh and not familiar with Lucas alternators but are they definitely low-side regulated?

Edited November 5, 2021 by nicknorman

[cheesegas]

12 minutes ago, Sir Nibble said:

First off, 13.6V is stupidly low, where are you measuring it? Agree with the 10A comment above,  whoever wrote that would have rejected every alternator I have seen in more than 40 years of rebuilding them. "Helpful" is not the word I would use for Sterling. 

13.6v at the batteries and the alternator. It climbs to 14.4v eventually, with or without the Sterling.

 

5 minutes ago, nicknorman said:

My 175A Iskra takes 4.25A field current when the field wire is connected to 13v, so a 70A alt is never going to take 10A. Although interestingly a lot of alternator regulator chips boast being able to supply 12A or more field current - not sure what alternator could take that though!

 

Anyway, you mention the current in the field wire but not the voltage across it. With one end of the field at battery voltage and the other end at 0v you should get max alternator output (only try this if your batteries are at a fairly low SoC) so you could try forcing the field to max current and see what the charge current is. This would show whether there is an alternator issue or not.

 

Edit: oh and yes, do check the voltage on the back of the alternator (B+) is also the 13.6v you mention, when the alternator is operating, to eliminate the possibility of some severe voltage drop between alternator and battery.

Thanks. I've never measured the field current with the old Sterling, nor any other one for that matter so I'm not sure what it's supposed to be! 0.5a seems low though. As mine's a neg field alternator I'll take the wire to ground and see if the charge current changes. With reference to ground, the voltage on the field wire with Sterling connected is 6v and disconnected 8v so it's doing something small.  Checked the voltage on B+ and batteries, the difference is less than 0.05v.

 

 

3 minutes ago, frangar said:

Me neither!!...I have however found Adverc to be incredibly helpful both with Brian the original owner and the chaps that own it now....I find Sterling kit to be poorly designed and built...

The old Sterling failed because a pair of resistors soldered in a little arch where there's room for just one on the PCB fell off. No idea on the value as said resistors are probably somewhere in the bilge... The new Pro Reg D (not the waterproof one) has got all the LEDs on a mezzanine PCB which is asking for the same thing to happen with vibration!

[MoominPapa]

If it would help, I have a brand new A127 regulator marked 14V going spare in the Nantwich area. (I've just installed a new alternator which came with this regulator and I replaced it with a "tractor" voltage adjustable one.) Free to a good home.

 

MP.

[cheesegas]

7 minutes ago, Tracy D'arth said:

Have you also checked the negatives?

Yep, less than 0.05v difference between any negative point on the system and the batteries.

 

 

Just now, nicknorman said:

Just thinking aloud, the field current is low. Field current is generated by the field diodes (assuming 9 diode machine), passes through the brush, rotor winding (which is a resistive load), brush,  regulator, to 0v. So presumably, with low side regulation if you connect the “field wire”, which I presume connects to the second brush, to 0v with the alternator running, you should get 4A or so field current and max output. If you get much less than 4A and not 70A or so generated, maybe one or more field diodes is blown?

Makes sense. Not sure if the field diodes are in the regulator or the diode pack on the A127 but I'll replace both just in case. As mentioned above, I'll take the field wire to ground and see what happens, will do it when I get back this afternoon. Thanks for the reference on field current too.

 

 

 

Thanks for all the help, I'm having trouble replying fast enough! Keep it coming...

[nicknorman]

Charles does like his through-hole mounted LEDs! Bearing in mind how cheap and easy lcd displays are these days, it’s a bit lazy Luddite!

[frangar]

6 minutes ago, cheesegas said:

 

The old Sterling failed because a pair of resistors soldered in a little arch where there's room for just one on the PCB fell off. No idea on the value as said resistors are probably somewhere in the bilge... The new Pro Reg D (not the waterproof one) has got all the LEDs on a mezzanine PCB which is asking for the same thing to happen with vibration!

I was asked to fit one by a customer....I told him there was no comeback to me if it failed at any point!....even basic stuff like the sharp edges to the box and no cable grommets or protection made me wince....the sole cable management seemed to be a cable tie inside the box.....I likened it to a poor O level project...and told Mr Sterling so....He in turn told me how much more profit I could make fitting his products than his rivals....inbetween swearing at me....lovely chap!

5 minutes ago, nicknorman said:

Charles does like his through-hole mounted LEDs! Bearing in mind how cheap and easy lcd displays are these days, it’s a bit lazy Luddite!

Its the Amstrad philosophy.....lots of flashing lights so it must be good.....

[cheesegas]

5 minutes ago, MoominPapa said:

If it would help, I have a brand new A127 regulator marked 14V going spare in the Nantwich area. (I've just installed a new alternator which came with this regulator and I replaced it with a "tractor" voltage adjustable one.) Free to a good home.

Thanks for the kind offer but I'm down south in Cheshunt - just ordered a 14v one.

 

 

4 minutes ago, nicknorman said:

Charles does like his through-hole mounted LEDs! Bearing in mind how cheap and easy lcd displays are these days, it’s a bit lazy Luddite!

A lot of complexity for seemingly no reason! Bought the waterproof version so hopefully the potting compound holds it all where it should be.

 

 

Just now, frangar said:

I was asked to fit one by a customer....I told him there was no comeback to me if it failed at any point!....even basic stuff like the sharp edges to the box and no cable grommets or protection made me wince....the sole cable management seemed to be a cable tie inside the box.....I likened it to a poor O level project...and told Mr Sterling so....He in turn told me how much more profit I could make fitting his products than his rivals....inbetween swearing at me....lovely chap!

Yeah, the old one was really badly made and the new ones aren't much better either! No grommets is inexcusable, and it mechanically relies on the solder joint which is crap for something so close to a vibrating engine...

[Tracy D'arth]

17 minutes ago, frangar said:

I was asked to fit one by a customer....I told him there was no comeback to me if it failed at any point!....even basic stuff like the sharp edges to the box and no cable grommets or protection made me wince....the sole cable management seemed to be a cable tie inside the box.....I likened it to a poor O level project...and told Mr Sterling so....He in turn told me how much more profit I could make fitting his products than his rivals....inbetween swearing at me....lovely chap!

Its the Amstrad philosophy.....lots of flashing lights so it must be good.....

I can only speak as I find.  But then I didn't insult Charles by telling him his product was an O level project...................

[Tony Brooks]

28 minutes ago, cheesegas said:

13.6v at the batteries and the alternator. It climbs to 14.4v eventually, with or without the Sterling.

 

Thanks. I've never measured the field current with the old Sterling, nor any other one for that matter so I'm not sure what it's supposed to be! 0.5a seems low though. As mine's a neg field alternator I'll take the wire to ground and see if the charge current changes. With reference to ground, the voltage on the field wire with Sterling connected is 6v and disconnected 8v so it's doing something small.  Checked the voltage on B+ and batteries, the difference is less than 0.05v.

 

1. As it should because the Sterling can't do anything until the in built regulator starts working. Then the Sterling can override it.

 

2. The rotor windings are typically around 3 to 4 ohms so in theory at 12V that should give a rotor current of 3 to 4 amps but that will only be while either regulator is juts sitting there waiting for the voltage to rise to the point they can starts working. Once they work it will be a rapidly pulsing current so a sampling digital ammeter could be all over the place.

[frangar]

10 minutes ago, Tracy D'arth said:

I can only speak as I find.  But then I didn't insult Charles by telling him his product was an O level project...................

I was only telling the truth! What sort of professionally made product leaves wires to rub on a sharp metal casing edge? Especially one that’s made to go into an area that might be subject to vibrations? Hopefully he’s made it better by now….

[Sir Nibble]

Now we have field current quoted at 13A?????

First thing, whoever wrote that has no idea at all, none, ignore them and reject anything they say or do. It sounds to me like a positive output diode failure. Check and compare voltage at B+ (output) and D+ (warning light) terminals with engine running. Should be the same give or take about a quarter of a volt.

[cheesegas]

38 minutes ago, Sir Nibble said:

Now we have field current quoted at 13A?????

First thing, whoever wrote that has no idea at all, none, ignore them and reject anything they say or do. It sounds to me like a positive output diode failure. Check and compare voltage at B+ (output) and D+ (warning light) terminals with engine running. Should be the same give or take about a quarter of a volt.

Don't know if you've read a Sterling manual, but it's pages and pages of badly written small text with cryptic diagrams in there. At one point, it says the field current will be up to 10a, but the in the specifications of the device a few pages prior, it says a maximum of 13a. Hmm. 

 

B+ and D+ voltages are identical.

[Sir Nibble]

Odd one. Sounds like a low performing alternator. Yes, I've read the manual just before phoning, being told that it must be remembered that an alternator is only a single phase machine, and giving up! Probably the same bloke who thinks 13A is a credible field current (it's actually what we in the trade call "burned out").

[Tracy D'arth]

10 minutes ago, Sir Nibble said:

Odd one. Sounds like a low performing alternator. Yes, I've read the manual just before phoning, being told that it must be remembered that an alternator is only a single phase machine, and giving up! Probably the same bloke who thinks 13A is a credible field current (it's actually what we in the trade call "burned out").

I cannot understand how the small brush gear in an alternator would continually pass 13A without problems. Which is why I queried the quoted 10A figure.

[nicknorman]

I think the point is that the electronics in the Sterling alternator controller is CAPABLE of passing 13A, not that 13A is necessarily the expected current. My alternator regulator is CAPABLE of passing 12A, but I only get a max of 4.25A

[Sir Nibble]

Field current aside. It sounds like the alternator is struggling against load to raise voltage. In other words,  bulk phase. The low current suggests a faulty alternator. I've just thought of a test for negative diodes. Check and compare AC voltage between W and B+, and W to negative. Again, the readings should match. 

[Tracy D'arth]

6 minutes ago, Sir Nibble said:

Field current aside. It sounds like the alternator is struggling against load to raise voltage. In other words,  bulk phase. The low current suggests a faulty alternator. I've just thought of a test for negative diodes. Check and compare AC voltage between W and B+, and W to negative. Again, the readings should match. 

Good call, forgot that one.  Don't have the engine revving too much, your meter may not read AC well at high frequency.