MG-Cars.com
MG Midget and Sprite Technical More problems! BBS discussion at MG-Cars.net
MG-Cars.net
Welcome to our resource for MG Car Information.
Recommendations
Parts
MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.
|
|
MG Midget and Sprite Technical - More problems!
| Hi all, Please help me again as I am now completely lost. Car details - 1275 Mk3 123 tune dizzy alternator (just converted from dyno with regulator box removed) I have finally got the vibration sorted (Tuesday) and the poor battery charging hence the alternator conversion (before Christmas). After the test drive following the vibration fix, as I pulled into the drive, the engine began to hunt in a big way with the rev counter needle jumping from a few hundred to 2 or 3 thousand revs and then back down again. It was at a frequency of around 1 cycle a second. It did not stall but kept going up and down. Pressing the throttle pedal had little effect on the engine hunting. On switching the lights off the engine ran smoothly again albeit with a slightly higher tickover, perhaps 1200 instead of 1000. Turning the lights on again and all was still ok. I parked the car up and hoped it would all be ok. Today my daughter has been driving the car and she reports that after 10 miles or so it is playing up again. She has had to abandon it and walk home. On the phone to report the problem to me she tried to start the car and all she got was the solonoid click. I have not looked at the car yet but will do later today so I cannot give any more details. One would assume it is due the the dyno replacement as it ran fine before this. Saying that it has done a good 400 miles since the conversion without any problems. I did have to remove the LHS wing to retrieve a socket at the same time as I did the vibration fix (Tuesday). To do this I had to disconnect the LHS headlamp. After I first had the issue I checked the headlamp connections and all seemed ok. Has anyone got any ideas to what is the problem? Thanks for your help. Dave |
| Dave Brown |
| Dave Please describe what you did for the altenator conversion, e.g. did you retain the old regulator? A |
| Anthony Cutler |
| Hi Anthony No, I removed the old regulator. I connected the three thick wires together and connected the two thin wires together. I cannot remember the colours of the wires but I will update you when I get home. I did post a question on here and updated it with what I did in the end. I did not add a new wire from the alternator to the battery side of the solonoid as I did not have any wire thick enough and was told that this was not needed. I am off to tow the car home now. Dave |
| Dave Brown |
| Hi Dave If I remember orrectly you had the 3 bobbin regulator And you should have connected the 3 wires together that were 2 brown and one brown with green tracer. This brown and green wire should be connected to one of the 2 large connections on the alternator the second large connector on the alternator should also be connected to these wires to help with the high loads when altenator is charging a flat battery. The small connector on the alternator shoul be connecte to the small brown wire with the yellow tracer. The original small brown and yellow wire that was originally connected to the small terminal on the dynamo can be used for this. Your problems ppear to be multifold. The first is that you were given very poor advice when you first attempted to chage the dynamo to alternator. This is easy if tackled correctly but must be one with all the facts and not generalisations about it is early the same as other vehiles, which it is NOT. Secondly if you ha a problem at xmas that you believe could be olved by fitting an alternator instead of a dynamo perhaps we ought to consider the oriinal problem? Why did you change to alternator, what was going wrong? Perhaps the battery is actually uff? perhaps you have a drain? an maybe numbe of other things. Anyway first of all get the car home charge he battery and try the car. |
| Robert (Bob) Midget Turbo |
| Hi Bob, Thanks for the info. I have the car at home now and will go out in a moment and check that the wiring is as you suggest. I don't think I have a drain as the car stopped working whilst the engine was running when the altrernator sshould be charging. I will check the wires and go from there. Dave |
| Dave Brown |
| Hi Bob, Just looked at the wiring and the small brown/green at the alternator had parted company with the connector. I have connected this up to the small brown/yellow (wl)at the regulator box. The small brown/yellow was connected to the F connector oat the regulator The other three wires (all thick, two brown, one brown/yellow) are connected together. As I see it the small wire is for the ignition lamp and would not affect the charging. Is this correct? Battery is now on charge. I will reconnect the small brown yellow to the Thanks for your help Dave |
| Dave Brown |
| Hi Dave Sorry to be a bore but something is not making sense. If you want to get this right you need to check the following. First please check the wires that are connected to the alternator The alternator should have 3 connections on it 2 large terminals and 1 small, check the colours of the wires you have connected to these terminals please I will hang of for the answer. |
| Robert (Bob) Midget Turbo |
| Hi Bob. You are not being a bore, not to me at least ;)The wires at the alternator are as follows - one thick brown/yellow one small brown/green These are the original two dynamo wires. I have not added the extra wire from alternator to batery side of the solonoid as I have not yet got any high amp cable or connector yet, it is on order and I was told that it is not imperative that this wire is connected, it will just make it a little more efficient. I hope this is the case. |
| Dave Brown |
| OK mate That is the confusion I always thought the large wire on the dynamo was the Brown and green. I thought the small terminal on the dynamo was a brown and yellow. However not to worry, just confirm that the alternator has 3 terminals 1 Small 2 large In your case you state the small terminal has a brown and green wire connected? this will need to connect to the brown and yellow that connects to the ignition light and was originally connected to the W connection on the control box The large terminal on the alternator that you say has now a large brown and yellow connected to it should now be connected to the brown wires that were originally connected o the B and B connections on the control box, or the main battery cable on the starter sol. If that is the ase then all should be fine Please be aware that I am not saying large or small wires but the size of the connectors on the alternaor. |
| Robert (Bob) Midget Turbo |
| Bob, Yes it is a bit confusing connecting small brown/yellow to small brown/green when there is also a big brown/yellow too. From what you say, I think the wiring is ok. My alternator does have two large output terminals and I am pretty sure they are in fact two ends of the same piece of metal. Studying the handbook wiring diagram, I cannot see that the small wire being disconnected from the alternator will stop it charging as it looks like it is just a feed to the battery via the ignition lamp so that it glows when the voltages across the battery and voltage out of the alternator are different. So perhaps you are correct and I have got another problem. Dave |
| Dave Brown |
| OK Dave We will see soon enough Just wondered what was wrong when you used the dynamo? I used my car with one for 20 odd years without issue and only fitted it with an alternator to get some photos for an article. :) My MGA still uses one to this day. |
| Robert (Bob) Midget Turbo |
| Bob, Just charged the battery a little, it is now around 12.5v and the engine runs ok. The ignition light now comes on with the ignition on and the engine not running and it goes out when it is running. Voltage at a very low tickover (about 700) and the voltage is around 13.3 at the battery. Does that sound about right? I have ordered the thick cable to connect the second alternator terminal to the solonoid and I will tidy up the regulator box ends at the same time. I swapped to an alternator because the ignition light was glowing right up to around 1300 rpm so I thought it needed new brushes at least and the lights were dim at idle and glowed brighter as rthe engine revved up. Yes brushes would have been cheaper and, in hindsight, may have been easier. I will check the battery voltage again in the morning. Dave |
| Dave Brown |
| That sounds right to me mate good job, I would expect the voltage to rise to about 14V plus when engine speed increased so looks alright for now. Nice one |
| Robert (Bob) Midget Turbo |
| Thanks for your help Bob. I still don't know why the battery drained or the engine started hunting so badly though. Dave |
| Dave Brown |
| Dave. Yes, the line to the ignition warning light is necessary for proper battery charging. At least, according to Paul Hunt who knows more about these things than I do. When I did my conversion, I cut out the control box entirely and simply ran the two heavy brown wires to the starter solenoid terminal where the line from the battery connects. Have never had any problems in almost as long a time as Bob has been trouble free. It woulds like your battery was not charging properly and the "hunting" was due to the fact that you were running the engine on an almost fully discharged battery--i.e. insufficient voltage. It would be a good thing to take a voltage reading at a somewhat higher engine rpm. Your 13.3 volts at idle is right at minimum, perhaps a little low. You should show 13.5 to 14.5 volts at about 1,500 rpm. If not, you may not be charging the battery adequately. The other problem is an alternator which puts out the correct voltage but insufficient amps to both run the engine, any accessories which are on, and charge the battery. But, this needs to be checked by someone having an amp meter who can check the alternator output under load. Les |
| Les Bengtson |
| I'd leave the barrety on charge to help with your diagnostics later 12.5V isn't very high I think you should be looking for 13.2v from the fully charged battery alone but Bob will confirm or say if I'm wrong |
| Nigel Atkins |
| Les, If it is correct that you need the ignition light wire connected for the battery to charge properly then I will be happy as it explains what has happened. I am sure if hte revs are higher the voltage will be up to 14v+. I will check tomorrow when the battery is fully charged. Nigel, I will check the voltage again tomorrow morning to make sure the battery is holding its charge and then put it on charge for the day. Thanks Dave |
| Dave Brown |
| Dave. Were I having this problem, I would make sure the battery was topped up with water, then charge it for at least 24 hours. Pull the battery clamps off and clean the battery terminals before charging. Then, when the battery charger shows fully charged, let the battery set for 24 hours before cleaning the inside of the battery clamps and reconnecting them. If the battery itself is bad, it will show up after being charged, but not connected, over the period of a single day. If the battery is good, leave the clamps connected, run the car at a fast idle--1,500 to 1,800 rpm, and check the output voltage of the alternator. If it reads between 13.5 and 14.5 volts, the alternator is putting out sufficient voltage. If not, the alternator is bad. One other area will allow a battery that is connected up to the circuit to go bad--a drain on the battery through the equipment it is powering (alarm/radio/any other full time on system). If the battery seems good and the vehicle is hard to start (low cranking output) after sitting for a couple of days, you might have some form of drain on the system. If so, post again and we can trouble shoot that problem. The alternator can, under certain circumstances, produce such a drain on the battery if its internal circuitry is bad. Les |
| Les Bengtson |
| I am not aware that the ignition light wire has to be connected to make the alternator work, nut I am unsure. However the only way a circuit can be made by this wire is if the ignition light bulb is NOT blown. If the bulb was blown the circuit is open and of not significance. Now if that were the case then eachtime someone had a charging issue then someone ought to suggest checking the bulb which I have never heard. I think I need to do a check in my garage at the weekend to see if that connection is vital. Nige a decent battery that has been stood for at least an hour or 2 will not exceed 13 volts when checked. Typically it will give a reading of 12.5 to maybe 12.8 somewhere in that area. Certainly a reading of 13.5 when the engine is running is a positive indication of charging. Naturally this depends upon RPM and this voltage will increase as revs rise. |
| Bob Turbo Midget England |
| yes I was probably thinking of a check just after full recharging the battery on a bench good point by Les about checking each cell of the battery for distilled water level before charging and making sure battery lungs and clamps are clean not sure about 24 hours but you might want to leave battery to settle for a while after charging before moving or reconnecting then of course reconnect securely and protect lugs and clamps |
| Nigel Atkins |
| On most old internal reg alternator the power to the regulator is supplied by the ignition switch via the ignition light. If it's not connected the alternator won't work. This small amount of current through the light, about 0.25 amps is enough to power the regulator and excite the field. It's not enough field cuurent for any real output of the alternator but enough to get it going and self excite. This self excitation powers the regulator. Once it gets going the regulator is powered by 3 small exciation diodes in the alternator (not the main diodes). These excitation diodes supply all the power required to make the regulator work and supply the field current (approx. 3amps) needed for maximum altrernator output. When the alternator is charging battery voltage placed the IND terminal on the alternator. The field wire then has +ve on it all the way back to the light. The light then has +ve on both sides of it and it then goes out. If there is a break in the wire from the ign to the alternator it won't charge but you won't have a light telling you so. Too small a globe i.e. less than 3 watts can also cause problems as there mnay not be enough current for the regulator to get going. Bob if you have a charge problem check the globe is ok. :) Pulling the field wire off the alt (IND or L) and touching it on earth will soon tell you if this part of the circuit is ok. I used to be an auto electrician and lucas alternators were good business, but not good if you had one on your car. |
| Greg H |
| Hi Greg No I do not have charging problems I was trying to help David with the original post. I was speculating whether or not the ignition light needed to be connected to help the alternator work, I didn't expect it would however you have explained the situation and have if I have understood correctly that it will not work without that connection. I must admit to doubting that because of 3 reasons. 1 would the slight residual magnetism be enough to excite the windings? 2 why could the excitation be taken from the main battery connections? 3 why have I never heard of the ignition light bulb blowing be the cause of battery not charging? Those were the considerations I had previous to your post. I had suggested testing in my garage simply to try the theory of charging without the ignition lamp purely as a test and not because I have a problem. :) Anyway when you say old do you mean modern alternators do not require this connection to work? |
| Bob Turbo Midget England |
| Greg, Thanks for your explanation. It explains why I had the problem and the battery went flat and why, when I switched the lights off the engine ran better when I first noticed the hunting. I only wish you had posted 'Don't get a Lucas alternator' earlier! Can you confirm that the ignition light bulb should be greater than 3w? What watts should the bulb be? Thanks Dave |
| Dave Brown |
| the 3w bulb has me confused anyone, like my good self, who has possession of a owners/Driver's Handbook has the answer literally at their figure tips :) (Ref: 0057) - http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html page 35:- Ignition warning - all markets except North America, Sweden, and West Germany 12v, 2.2 watts, GLB 987 I think I changed my ignition bulb a couple of years back and would have used a 2.2 watts on the then a Lucas alternator |
| Nigel Atkins |
| Bob I know your car was ok just responding to your statement "eachtime someone had a charging issue then someone ought to suggest checking the bulb which I have never heard" :) 1. Residual magnetism doesn't do enough. Although I'm sure there are instances where it has worked. 2. If it was powered by the battery the regulator would always be powered even when the car was parked in the garage so needs IGN to tell it when to go. 3. Ign light lasts a long time as it's not on that often. But when you turn your ignition on it's worth checking the light is on before you start the car. Alternators on newer cars, probably since later 80's often have two wires. An IGN feed for the regulator and a seperate wire for the light just for driver indication. It will charge as long as it has IGN feed to it. But all manufacturers are different. Lights about 3 Watts but not that critical and if the manual states 2.2W then that's obvioulsy what it should be. I just recall times when people put little globes in and it stopped charging. They may ahve been 1W or so but don't know how small before there's a problem. Dave Lucas isn't called the "Prince of Darkness" for nothing. A Lucas alt keeps it original but if you don't care I'd put a small late model alternator on it off a Japenese car, but over there there may be other good ways to go. Doesn't really matter what you fit what ever is easiest and actually fits on.They all work the same but like everything things have improved a lot since our cars were built |
| Greg H |
| This got me thinking too. I’ve never come across a fault checker that said make sure the charging warning lamp is good. But thinking about it. ---- Going back to first principles from my old college theory notes .— For an alternator to work, its rotor must turn inside a magnetic field. Initially the magnetic field is produced by applying an external voltage to the non moving field windings, which causes a current to flow through them, --an excitation current. This can be done by connecting a lamp or resistor via a switch from a battery in series with the field windings. When the switch is turned on, current flows from the battery, through the lamp or resistor and field windings, and provides an initial magnetic field for the rotor to turn in. Once the rotor is turning fast enough, this enables the alternator to produce an output voltage. The output voltage is fed back to the field windings, and it becomes self exciting. At this point current ceases to flow in the lamp or resistor. So, in theory. unless there is either an external current source, or residual magnetism in the field of the alternator, the alternator can’t produce an output and can’t self excite. So if the lamp or resistor is open circuit, or taken out, the alternator won’t produce an output voltage. ---. In theory. Chances are though, I would reckon there is always an amount of residual magnetism in a previously used alternator. And even new ones have probably been tested, and therefore also have a level of residual magnetism too, -- and once the rotation reaches a sufficient speed, it will self excite and produce an output voltage. But, if the lamp or resistor isn’t there, maybe at low revs it wouldn’t be enough to charge a battery. So you can’t really do without the lamp or resistor. Maybe, if you got a value of resistor right, you could wire one up in parallel with the lamp, so that if the lamp blew, there would still be a path for excitation current. But getting the value of resistor right would be tricky, -- I think. |
| Lawrence Slater |
| there has previously been dicussion on here about this I'm sure but as usual I can't remember the outcome I think I remember something about a bulb coonection but as I can't back it up I'll have to look later after I've been for yet another roof down dry and sunny drive in winter :) |
| Nigel Atkins |
| Needs the light to work. Some cars not Lucas mostly but the first alt equipped MGB did/do have a parallel resistor to keep it working if the bulb blows, which is pretty useless since the bulbs never blow except when there is a fault in the alt/reg. This particular fault causes the system to go unregulated, which fries everything, until it is dead dead. I had this on an Austin - the light goes out when you start the car, but glows dimly. As you increase engine speed, it gets brighter as the voltage rises to around 18 or 20V, headlights are REALLY good! Then the bulb blows and the thing quits charging. I used to carry spare bulbs as I didn't have the shekels for an alt, but every time I got frisky and took it up past about 4500, the damned lights would go out. Some early Lucas alt systems used a field isolating relay and an "assimilator", instead of using the light for excitation. If you get an early Rover or Jag with this, have fun sorting it! FRM |
| FR Millmore |
| Nigel, you are right it has all been discussed here before. When l changed to altetnator on my 71 car about 4 years ago it was all explained to me then. At the time it seemed to be common knowledge that everyone except me was aware of ! Now it seems everyone but Greg and Fletcher had forgotten about it !! |
| Guy |
| Brain cells Guy, ever leaky for most. :) Memories fade. Good that they do. The archives are great, but nothing like as informative and interesting as a live rehash of a subject. imo.:) |
| Lawrence Slater |
| LoL Lawrence! I gave up on the archives ages ago. I just can never find what I want there. I use it occasionally but just sort of wander around in there looking at random discussions. The search options never for me bring up what I am looking for for some reason. There are those that say what a fantastic resource it is but unfortunately I don't seem to have the right index! Regards the alternator/ ignition light. - sometimes when I go to start my car I switch the ignition on and the bulb doesn't light up, but the car still starts when I press the start button. The light then glows on and immediately off again as the engine fires up. It has done this for ages, maybe 1 in 3 starts, but other than that seems fine. I think it is just one of those oddities of ownership but maybe its a portent of problem, a failing alternator? Should I be have a worrisome 2012? |
| Guy |
| Guy- Most common reason for that behavior is bad connections, in this case specifically but not exclusively, in the W wire connectors under the dash, especially doubles. Since these will sooner or later cause failure of all IGN controlled functions, usually in an intermittent hence maddening form, I suggest you check and replace all the connector sleeves. Also, any connection in the IND lead to the alt, including the bulb/socket and any dicey things that might have been introduced in the conversion. As I've said a million times, the sleeves crack with age, and they are all past expected lifetime now; they make a poor and intermittent contact when cracked. I used to find bad ones occasionally; recently every double and most singles are cracked on any car that hasn't been attended to. There are about 10 single and 20 double connectors per car, for a total of about $10US. I use OxGard on these and all connections and bulbs, a special grease that ensures good contact, but any form of grease will do. Much better to fix these at leisure than chase gremlins forever, and everything works better after you do it! And it will usually stop all those enquiries re poor turn indicators and dim side/tail lamps. FRM |
| FR Millmore |
| FRM, Thanks for that advice. I will check out the wiring connections under the dash. I have a stock of bullet sleeve connectors an and have been replacing them and when I am working on any particular circuit. But haven't done the behind the dash ones yet. I also use a electrical contact grease called Durite on any connections that I re-make. |
| Guy |
| Guy, the discussion or thread I'm thinking of was more recent than 4 years ago I'll see if I can find it in the Archives (that I'm hit, miss, miss, ect. at) |
| Nigel Atkins |
This thread was discussed between 05/01/2012 and 08/01/2012
MG Midget and Sprite Technical index
This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.