The 'E' Type Forum

I keep suffering from my battery spilling acid from the top filler lids and I want to check that my dynamo/regualtor is not overcharging. The battery charges very well indeed and the dynamo was overhauled professionally and then I fitted a new manufactured RB340 regulator. I do wonder whether the regulator is allowing too much charge but not sure how to check this in spite of the instructions in the book. Can anyone talk me through this? Is this the cut in voltage or drop off voltage or the current regulator? There is quite possibly nothing wrong with the set up, it may just a battery that leaks, but since its the second battery I have suffered this with, I feel I must at least check the battery is not being over charged. I have an AVO analogue meter on its way to me as I know digital meters are not good for this sort of work. I am interested to learn about this dark art.

Simplest test is to put a voltmeter across the battery with the engine running - when revved to 3,000rpm it should read 14.3 volts. Any higher and you have a problem.

ok, well that sounds simple enough! thanks David. However, what if its charging it at 14.3 Volts regardless of the underlying state of the battery. i.e overcharging it? I mean if you charge a 12v battery at 14.3 regardless of the drain surely that would still overcharge it?

No, doesn't mean it's Charging at 14.3 volts all the time, it's just reaching that. I believe a normal figure is 13.7 volts to 14.7 volts max, with engine running, and with everything on (wipers, headlights etc,) it should still be 12.6 volts or more
If it never exceeds 14.7, it can't be overcharging.

Malcolm et al are spot on...look for around 14.2-14.5 volts at 3000rpm....any more and the unit is dud...and they are a pain to set up correctly once they malfunction....

Owning an mg with an RB340 as well as the E I now have several in my shed and most are duds. My experience with the new manufacture copy units has been universally rubbish. Some are not even electrically the same internally as the genuine Lucas unit either. I have had two start overcharging with the battery terminal voltage reaching 17.5 volts.....touch wood the genuine article in the e type works fine....the one in the mg I scrapped out the junk innards and fitted a electronic replacement....but that is another story

oooh Thats sounds bad. I will check the voltage across the terminals and report back . May be a while as I have the battery out currently and doing some other works. Lets see what it charges at and report back from there. thanks chaps, as always
Andrew

I had a MK2 Cortina on which the regulator packed up and the dynamo over-charged to the point that the battery acid was boiling and spewing out of the battery. It sounds like you have a similar problem.

I had the manual to adjust the regulator but it was hopeless. IIRC the contacts fused together on one of the coils which meant it wasn't making and breaking. No amount of dressing of the contacts would stop it happening.

Fortunately, in those days, you could visit a local scrap yard and find what you needed easily enough.

Regards

If it were me I'd just take the car to an auto electrician.

You can take it to an autoelectrician but really there is not a lot more they can tell you . The RB340 has three solenoid coils and three contacts. One is the low volts cut out that isolates the dynamical the battery at low dynamo output voltages....or when the engine is off. If it does not then the battery discharges back through the dynamo...bad. This section is also connected to the ign light. The other two are current and voltage sensitive. One will open its contacts if the current from the dynamo exceeds a set amount....usually around 22-30 amps depending on the dynamo it is calibrated for. The other will open if the battery voltage exceeds around 14.2 volts and protects the battery from overcharging.

Both the current and voltage reg contacts will open and close rapidly at times and are prone to contact wear that alters the current/voltage regulated level, and also to contacts welding together leading to either overloading the dynamo or overcharging the battery. The contacts can be cleaned using wet and dry paper and soldering 100 nanofarad capacitors across the contacts does reduce sparking and wear....and improves radio reception....but 're calibration of an RB340 requires patience and some test gear (a meter good for 30 amps D.C.) that most don't have. Easier to replace with a new one (usually crap) or Known good NOS one.

it was for the above issues with c...p replacements etc that i switched to a lightweight Alternator. Fit and forget.

Thanks Julian, very helpful. I have suffered with these on all sort of vehicles over the years. My first experience was on my Willys Jeep, not a Lucas unit, but the same sort of thing. Its definitely a dark art. I had a chap in Kent who was a wizard with these things, but he is ill and not working. Finding any other Auto Electrician that even knows what they are in this day and age is a task in itself. I have read about electronic conversions and have fitted a few in old motorbikes, but was hoping that as these are newly manufactured they may work. Perhaps I am being too hopeful. Anyway, I will have to suspend the rest of the story until I get the car started again. Just fitting an adjustable reaction plate and new Tbars , will move onto the charging after that. thanks chaps.

I had been considering retro-fitting a dynamo as part of the final re-commissioning of my 3.8 but have decided to go the +ve earth Dynator route with the RB340 acting as a dummy unit. The control unit and relay are built into the Dynator. This keeps looks original but improves the charging at low speed and takes reliability issues (hopefully) off the table. Are you totally wedded to the Dynamo/RB340 for originality?

Ah Phil. I had forgotten that as an idea. I saw these Dynators at one of the shows and the dummy RB340 and made a mental note....and promptly failed to recall it until your jog. I will look into that, if I can establish that the dynamo is overcharging the batter. Maybe a better long term solution. thanks for reminding me.

Dynators are an option but in defence of the good old dynamo providing you can get a genuine Lucas RB340 that works the system is ok. My e type has an old (original?) Genuine Lucas RB340 and it has worked perfectly for the five years I have had the car.....all I have done is refurbished the dynamo with new brushes and a good oil and cleaned the RB340 contacts with switch cleaner...

I've been in dinosaur land too with an RB340, dynamo, +ve earth since I bought the car etc about 15 years ago and apart from'checking and adjusting the RB340 about 4 years ago have never touched anything, maybe because the regulator was NOS.

I wrote an article on my experiences on the Forum in 2013 including a simplified version of the adjustment instructions, can't see on this tablet how to copy the link (PC currently at the breakers) but if you search for RB340 AND rfs1957 it comes up.

All the images and diagrams have been fritzed by the swine at PhotoBucket, but if - from reading the words - it sounds helpful, then upon request I'll dig out the images and stick them up again.

Thank you Rory. I will do just that and have search. I bought myself an AVOMETER to do all this testing with, but now diverted trying to get that to work!! will report back in due course.

I hope it was a proper vintage avometer. I love em The model 8 mk4 is a fabulous instrument with a superb damped meter movement. The ideal instrument for setting up the voltage cut out....

Its a model 8 MK5. I just got it working, well on voltage. Seems pretty accurate. Now need to teach myself how to use it. I have always despaired of digital meters for some tasks, as they are just not static and bounce around all over the place. I am hoping this is going to work on resistance and current as well, but as I am not an electrical engineer its testing my schoolboy physics. The good news with the meter I have bought is it has all its original leads, some probes, clip on and crocodiles. They tend to be hard to come by. Are you an expert, if so we may take this off line and explore some basic lessons for me?

OK boys, you asked for it.

I have resuscitated all the old pictures, weeded out all the changed punctuation marks we got stuffed with when the Forum changed platforms, and generally wasted a couple of hours, so let's hope this is of some use to someone.

I must have been a lot brighter and sharper when I wrote this as reading it today (2017) freaks me out and would have me reaching for my cheque book and an alternator, however I obviously DID manage what I wrote and the car has worked perfectly ever since.

EDIT - re-establishing photo links and editing this in 2020 makes sobering reading - I was indeed a lot brighter in 2017 and in 2014 ! It's been downhill all the way, as I've since bought a Dynalite from Powerlite at DY5 3SU .......

Here goes :

Reading all the advice about adjusting the RB340, and other E-Type boxes, available in all sorts of different forms on the net, gave me a headache, and had me going around in circles. At one point, convinced I'd managed to bugger my genuine-original NOS one by my cack-handed adjustments, I was about to chuck it out and buy a solid-state one ....




I offer here a synthesis of the reading I did and ended up applying with success, using the words of one syllable I would have liked to have stumbled across, written for a complete f----wit, in the hope that the many hours I wasted will be of some use to others.

Much of it is relevant to other control-boxes, not just the RB340.

I know from experience with engine-dynos that I tend to lose my wits and reason when confronted with revving engines and twitching dials, breathing carbon monoxide and waiting for rods to come through the side, so I made myself up a set of cards to slide under the control box during each of the 4 operations so that all was to hand and simplified, aimed at the intoxicated f----wit.

You will need the relevant reference pages relating to these control-boxes from the original Lucas Handbook, as of April 2020 this link still worked,

http://mgaguru.com/mgtech/books/pdf/Luc ... _Tests.pdf

It theoretically does contain all the necessary information, tho' I found misleading and indigestible - which is why I wrote this lot in fact.

Things to note :

A. With the original 3.8 harness, the regulator is fed from the battery with NO fused protection whatsoever - the brown/white wire feeding the B-B terminals is permanently live and mega-powerful ; if you were to manually close the Drop-Off contacts during any adjustments, they can weld shut and you can fritz the wiring harness back to the battery, and probably end up with a fire to extinguish. I consider it absolutely imperative to fuse both the brown wires that leave the battery/starter-solenoid interface ( one goes to the ammeter, the other to fuses 3 and 8 ) before you do anything to the wiring on a 3.8.

See for details : viewtopic.php?t=5214&highlight=

B. The revs expressed in many publications relate to Dynamo revs, NOT engine revs, so you need to be wary of what you read - and be kinder to your engine, because 3.000 dynamo rpm, for example, is actually only 1.800 engine rpm on my car (pulley diameters give you the proportion, mine are approx 80mm and 130mm, dynamo speed is 13/8 times engine speed etc).

C. The advice regarding which way to turn the cam adjusters is very misleading - Lucas refer to the direction in which their tool with its integral pinion is turned, but since we'll all be using long-nosed pliers directly on the cam, the directions are then reversed - counter-intuitively, it is CCW to increase any reading, and CW to decrease it.

D. My car has the C42 dynamo, and the figures shown may be different if you have a different one - suggest you consult the Lucas book.

E. The tests are meant to be carried out within 30secs of starting the engine so that heat build-up in the regulator coils doesn't skew the readings ; I got somewhere close no matter how long it took, then waited 5 minutes for everything to cool and have another go - it didn't frankly seem to make a lot of difference.

Preparation consists of

1. getting a decent shunt ready (see photo) for bridging the two 9.5mm spade connectors of the brown-white wires from the RHS terminals B-B (which are in fact common) once they?ve been disconnected from the regulator, I used three flat 9.5mm spades riveted together so I could also have a solid connection to an ammeter-wire for the Current Test.





2. removing the brown/green off the W-L (Warning Light) spade, and replacing it with an insulated spade plus short wire to facilitate its connection to a voltmeter.

3. finding a way of holding an accurate moving-coil voltmeter on a clamp or w.h.y. so that it can be used hands-free.

4. setting up some Heath-Robinson jury-rig so that the throttle can be operated from the regulator area - even if you have a second pair of hands and feet to help, I still think this was 15 minutes well spent, notwithstanding its disgraceful construction out of some scrap timber and a few dry-walling screws ; don't tell anyone I made this please.



I suspect that you can do these adjustments in whichever order you choose but like a good soldier I did them in the Lucas sequence.



1. CURRENT - see Lucas Handbook pages 18, 19

This requires either an inductive clamp that will do DC or a serious industrial meter like this one I got for £15 on E-Bay :

http://www.ebay.co.uk/itm/AMMETER-0-40- ... 3f2c38b29b

Use a crocodile clip to hold the points shut and bridged on the LHS/front of the RB340, and with the brown/whites disconnected from their B-B terminals and shunted together, connect them (via the shunt) to the -ve terminal of a 0-40 amp ammeter, and the +ve terminal of the ammeter to the B-B terminals on the regulator. Start the engine, switch the headlamps, panel lights, heater fan etc and run the dynamo up to 4.500 rpm (whatever engine rpm necessary for this, 2.700 for me) and check the maximum current - for the C42 used on my car this should be adjusted to 30A +/- 1.5A.





2. VOLTAGE CAM - see Lucas Handbook page 20

This determines the charging voltage seen by the battery. Once wired up as per diagram, run the dynamo to 4.500 rpm (2.800 engine rpm on my car) and set the cam so that the voltage is about 15v - on my car the cam adjustment is very sensitive at this point. There is a Lucas table of corrections for temperature, but essentially the tolerances are large and 15v is shown to be acceptable for temperatures ranging from 10°C up to 40°C ambient. If you've got an odd battery (I'm using a modern Spark-900) then you may need to adopt a different reading here, mine requires a maximum of 14.7v. From what I can see the revs are actually irrelevant once you have reached the peak - from about 2.000 engine rpm upwards the reading is stable on my car.

3. CUT-IN CAM - see Lucas Handbook page 23

This is misleadingly labelled as a cut-out relay on some diagrams. First the brown/whites go back on their B-B terminals, and the voltmeter goes between the temporary wire on the W-L terminal and earth. Run the engine, then watch carefully the pair of contacts that are between bobbins C and C.IN (that's centre and right, of the three) - these points will start off open, then as the revs rise there will be a click and they will close. It is the voltage reading when they close that is critical - between 12.6 and 13.4v is correct. The C.IN cam is adjusted to obtain that reading - I just aimed for 13v. All the books talk about watching for a jerk in the volt-meter reading as showing the points closing, but I found this very hard to ascertain and the visual method was much more reliable.

4. DROP-OFF CONTACTS - see Lucas Handbook page 24

These are the same ones you've just observed when adjusting the Cut-In cam. Start by disconnecting the brown/whites from their B-B terminals, and connecting them together again with the shunt, as per for the Voltage Cam. Fit a voltmeter between the BB terminals and earth. Then rev the engine to about 2.000 rpm (should see 13 - 14v or so) and let the revs drop slowly ; the voltmeter reading should drop gently, then fall suddenly as the contacts open - this fall should occur at a value between 9.5 and 11v. The adjustment of this requires bending the fixed contact arm, I found that I could bend it just with pressure from a long insulated screwdriver ; pliers would be inviting shorting something out I fear. Reducing the air-gap will increase the drop-off voltage reading, whereas increasing the air-gap will reduce the voltage. I just aimed for 10v and found it quite easy to tweak the position with the screwdriver.

The cover on my car was held on by a two ghastly sort-of black nylon reusable pop-rivets, which I couldn't live with even if they were original - 5mm rubber Well-nuts require the back-plate holes drilling out to 9.5mm, and then you can use conventional screws ; I promise to replace the dome-headed Allens with something more "period".





HERE ARE THE CARDS TO PRINT OUT THAT MAKE IT EASIER TO REMEMBER WHAT YOU'RE TRYING TO DO WHILST BEING ASPHYXIATED BY ENGINE FUMES AND DEAFENED BY THE EXHAUST NOISE :

Well done Rory everything anyone could ever need to know...

For those who have only ever used a digital meter if you use one here it will probably wonder about as the dc voltages here are very "rough" with all sorts of spikes and noise...digital meters tend to sample and measure the instantaneous voltage and then display it. Chances are each sample measure will be different hence the display jumps about....expensive meters such as Fluke can have an average facility which helps. However an analogue meter cannot jump about easily so shows an averaged reading anyway....which is ideal for this job. And the Avometer was the pinnacle when it came to analogue meters with it deliberately damped meter movement...if you can get one they make a great meter for General diagnosis of classic car electrical gremlins. They do D.C. and AC volts (up to 3000 volts!!!. D.C. and AC amps (10 amps max) and three resistance ranges. The resistance ranges need one D cell and a 15 volt battery which you can still buy from the internet...and the meters often pop up on eBay...