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MG MGA - charging problem

Hi Folks. It seems my MGA 1500 has a charging problem. My voltage regular crapped out in the spring, and I replaced it with a new one. The battery seems to have been charging well ever since, and the ignition warning light has been staying off except at idle, when it glows dimly (as it should). In the last few weeks though, the battery has been dead several times, and my car consequently would not start. When the battery is recharged, the car starts right up, just fine. So sstaarter motor, starter switch, battery cables etc, are fine. With the dead battery, when the starter button is pulled the engine (Obviously) turns very slowly. Jumping the starter switch with heavy cable gets the same slow cranking speed, so the starter switch is good. The generator is good, since the car runs with the battery ground cable disconnected. I also removed the generator, hooked it to a battery, and it does "motor". The fan belt is tight (but not excessively so), the battery terminals are clean and tight, and the wires attaching to the generator are clean and tight. The motor mount ground cable is attached to clean grounding points, and the bolts are tight. The battery was tested (after recharging) with a hydrometer, and all cells are good. (I tried a different battery in the car, and it goes dead after a few days also) The starter motor has been tested and is good, as is the starter cabling. The main (long) battery cable has been replaced with an upgraded (thicker) cable. The battery is not being drained when all accessories are off because I tested for this with a test light. (Between battery post and battery cable) The terminals on the fuse box and voltage regulator are tight and clean. I am assuming that the voltage regulator is good because it is brand new, and has been worjing fine. The ignition warning light is still working properly (goes out at anything over an idle, yet the 2 different batteries that have been installed does not seem to be charging. Does anyone have any idea as where to look next to track down the problem ? I am running out of ideas! :-( thanks! Glenn
Glenn

You have pretty well covered all the bases. I think your neighbour is sneaking over at night and turning your headlights on!
Mitch Smith

Glenn. I agree with Mitch. You have covered most of the bases. The first thing I would do is to disconnect the battery (ies) from the system and let the car sit for a day or two. If, when you reconnect them, you still have the problem, the battery is the root cause--it will not maintain a charge.

If you can disconnect the battery for several days, reconnect and it works properly, there is some form of drain on the system. The battery is being drained even though the test light does not come on when connected in series with the non-grounded cable. You are, then, beyond my level of competence. Go to Paul Hunt's Website, The Pages of Bee and Vee and contact him for more thoughts. Paul is a highly qualified electro-mechanical engineer who should be able to provide you with more troubleshooting techniques to determine what the actuall problem is.

One of them, now that I consider this is sticking points in the new voltage regulator. Had this problem with a 53 Mercury Coupe that my parents bought me as a first car. When I went to get a new battery, the "mechanic" installed it backwards, not being aware that US cars had, back in 1953, positive ground systems. We discovered the problem when our next door neighboor, and old Ford Mechanic, glanced at the set up, told us the battery was trying to drive the starter as a generator, reversed the connections, gave the mechanical voltage regulator a whack with a screw driver and said, "Problem solved". I drove the car for another year without problems. Up 'til I could get myself one of those Austin-Healey Sprites like my cousin had.

So, disconnect the battery and see what happens. Check out the new voltage regulator for stuck contacts, and, if that does not solve the problem, contact Paul Hunt.

Les
Les Bengtson

Glenn

I take it you are not using the light from the headlights to write your poems. The length of the prose would flatten most batteries!

Steve
Steve Gyles

I tend to think it's your regulator. The points on a new one even need to be cleaned. 400 grit, as many times as necessary. It's a good idea to clean the points with a q-tip soaked in alcohol after. I have found that any time I have a problem with the regulator, it's right after it rains. The car stays outside, and the moisture must make the points arc, burn, and generally tick me off. The last time, it stuck on, the lights were REALLY bright, the ammeter rising to max with engine speed. Luckily, I wasn't in a hurry, kept the revs low, and didn't burn out any lights or the battery.
Tom

I too think it MAY be the regulator. It could be intermittently sticking closed, causing the battery to drain through the field winding while parked and off. Normally this would not be the case. The cut-out contact is supposed to open and disconnect the battery from the field winding, but if it is a new regulator, it may be defective. Troubleshooting an intermittent problem is difficult at best. If the sticking contact is the cut-out contact, this would explain everything else checking out just fine.

Of course, it may be something totally differnt, but this is where I'd recommend you go next. You've already done a lot of testing on the common items.

Tom's symptoms would indicate the other set of contacts in the regulator sticking closed.


Chuck
Chuck Schaefer

Hi Folks. Thanks for the advice and comments. I will dig a bit deeper, and let you know what I find. Cheers! GLenn
Glenn

Recently I had a problem with my regulator. I had never pushed the electrics to the limit even though I had travelled into France on a number of occassions. Then at Silverstone this year the heavens opened and on the journey home I needed everything electrical to be on.
I had H/lights, blower, wipers all in full use for about a 3 hour journey. Just as I entered my home drive I noticed my indicators were not flashing. After stopping the car I tried restarting and had vertually nothing in the battery to turn the starter.
I checked the following day and found my regulator whilst charging atabout 12.5 volts would do no more. This is good enough to hold the ignition lamp off but is not enough to run the items I required. The result was a flat battery. Simple job was then required to adjust the regulator.
The point is of course for you to check the output of the regulator with a voltmeter across the battery when the engine is running and ensure the charging voltage is at least 14 volts.
Bob (robert)

The one test that you did not run is the first one I run when some one comes in with a complaint like yours. I load the battery and test the output of the generator in amps. The machine I use is larger and more $$ than you would have at home. This is the test that shows if the charging system is doing it's job. The objective of the generator is to make AMPs of current at the proper voltage. The test can be run with less costly equiptment. Using an inductive ammeter and a small battery load tester (what we call a toaster because the wires inside glow and get hot when used) and a volt meter. With an ammeter measuring the current through the output wire at the generator and a voltmeter at the battery rev the engine to 2000-2500 rpm and apply a load to the battery (to simulate a low battery). Watch the two meters volt should not exceed 14 ( if it does the v-reg has a problem, may need adjustment) Amps should be about the rated out put of the generator, though the MG service manual doesn't show and I don't know what that spec would be. I think the amps should be between 25 and 35 but I am not sure. If any one out there knows the amp rating of our generators please post. Remember ohms law, power measured in watts equals volts times amperes. W = V x A. Without both volts and amps there in no power to fill the battery and run the systems. With all that said the regulator is the most likely culprit.
R J Brown

That test using an ameter is totally unecessary, If the voltage is at 14 volts measured across the battery with the engine at 2000 rpm then the current will be as a result of the resistance of the circuit. If the battery is almost fully charged then the resistance will be high and thus the amps will be low. If the Battery is low then the resistance will also be low causing a high current flow. Simple ohms law as you point out.
The point being that the voltage across the battery is the key to the performance of the generator and regulator.
Bob (robert)

Chuck, you're right. The bobbin with the fewer windings (regulation) was arcing in my case. This was quite visible at night, when I had the problem. The points need to be clean or they will try to weld themselves together. I guess they're always trying, but get more sucessful at it as the surface deteriorates. The cutout is a bit tricky. It closes at a voltage (12ish?)..you can see it right after you start the engine (may have to rev it a bit, mine idles fast enough to close). But it doesn't open until after the engine is shut off. The spring is strong enough to pull the points open, but if they've tried to weld themselves together, there may be a current path to drain the battery.

I'm fresh off the control box thing, so these things are fresh in my mind. Ask me in a month what I just said, and I'll reply "huh?". The same applies to measuring the darn thing in 30 seconds, letting it cool down each time, adjusting, cooling, rechecking. I've never made any large adjustments to the factory settings. Cleaning the points really well is the main thing.

There are folks out there that put modern solid state innards in the things. I think I'd rather just carry some sandpaper in the glovebox. Might need it for the ignition points some time, too.
Tom

Tom, I was just thinking that an easier way to check that situation is to measure voltage on the field terminal of the generator. If there is ANY voltage, even a few tenths of a volt (so long as there is still some voltage left on the battery), it would indicate a sticking or arcing cut-out contact.



I know what you mean about being fresh in the mind. I mentally went thru the operation of the control box a few years ago to get a better understanding of how it worked and why it was done the way it was. I had a few moments of thought before I could get back into it.

I'm glad that the problem was that easy (and inexpensive) to solve.

Chuck
Chuck Schaefer

Bob your right using an ammeter is unnecesary you can do the job without one. But its like driving nails with a brick once you own the proper equiptment and know how to use it it sure makes it nice and easy. Don't pan modern equiptment and methods just because you dont understand them. I use a Snap On MT 3750 AVR to test starter battery and charging systems. I was trying to describe a way to simulate the tests we run with more common equiptment.
R J Brown

Yes Rick, is it Rick? but the point is unlike the MGB and more modern charging systems the MGA does not have a current (amps) cut out therefore it only has 2 adjustments. The first cuts in when the dynamo turns and the second on switches in and out to control the voltage at about 14.5 volts. Thus all that is needed to set this thing up is a voltmenter across the battery and a screwdriver to adjust the voltage contact. This is so simple it is easier than topping up the oil and should not be made out to be the big deal that it isn't!
Bob (robert) Used to have 2 cats

Bob (used to have 2 cats),

Do you use a digital meter to set voltage?

I tried it once and had some problems measuring at the generator. The electrical noise on the generator caused the meter to read high. When set that way, the idiot light would almost always stay on. Measuring at the battery would be better as the long wires tend to smooth out the noise, but I just have a small problem seeing the meter behind the seats from under the bonnet :>)

I switched to my trusty Simpson 260 analog meter(moving coil) and found the issue. Reset the control box using the Simpson, and all was well. Besides, an analog meter would have been what the factory used, no?

Different brand digital meters react differently to noise, causing an error in readings. If you don't have a second way to verify the setting, you would not know. I have run into this before in my vocation.

Just wondering if any other brave soul, who would dare mess with Lucas control boxes, has seen this effect.

Chuck
Chuck Schaefer

Chuck yes I must admit to using an analogue meter for this task. This due mainly to the refresh rate of a digital meter and the constant opening and closing of the regulator points tends to drive the meter bananas.
The other point you may want to consider when using a cheap digital voltmeter is the condition of the internal battery. I have seen where if you leave the meter switched on for extended durations and the battery within the meter is pretty poor the actual meter reading tends to go high! Not to reassuring!
Bob (robert) Used to have 2 cats

The control box is part of the mystique of owning one of these cars.

I must admit to not always taking the time to mess with them internally. Once, I put a used one on the car to check it out. Soon after, there was a smell of burning insulation. So it's a good idea while playing with this stuff to keep your battery connections loose enough to be easily depower the system and avoid more expensive damage. Use your nose as well as meters and such.

I think you can use a digital meter across the battery and it will read fine. The battery smooths out the voltage.
Tom

Tom,
I recently had to replace the yellow wire running between the generator and control box due to a bad box and/or generator (I replaced both). Of course, I had installed a new loom only htree years ago. I now have an in-line fuse on the yellow wire.
Joe Cook

Makes it tempting to put an alternator on, eh? Even with new control boxes costing about what an alternator would, I just can't change. I like to brag that it has positive ground, I guess. I'm a geek.
Tom

This thread was discussed between 22/09/2005 and 27/09/2005

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