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Ammeter - this is crazy?

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tomster Avatar
tomster Tom Dunbar
Annapolis, Maryland, USA   USA
OK, I've really been enjoying the TR4 the 6 day's Ive owned it. Today I drove up to get my tags.
Car ran pretty good. Came out an hour later and tried starting it - cranked but wouldn't start.
Some nice guy's helped me get it started with a jump and I drove it around the parking lot 3 laps
almost went out on the road and it died again.

The real bizarre discovery in all of this is I was talking to one of these guys about the ammeter and how
in the Triumph owners manual it says - when the needle is moving to the right it is charging and to
the left it is discharging. Well, he noticed the illustration is completely the opposite of my gauge
in that the positive is on the right and the negative is on the left (which makes sense). On my car it's
the exact opposite! confused smiley Maybe it's an English/American thing? I have an American spec TR4 and an
English manual? (I've noticed other things in this manual that make me wonder too)

So when I start the car and am driving the needle is always bouncing to the right (negative side for me).
Is my gauge made in China or something? Is it correct? Ok, I've babbled too much - see photo for the real story and please
set me straight on this. Thanks!

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tomster Avatar
tomster Tom Dunbar
Annapolis, Maryland, USA   USA
Ok. I'm guessing that my ammeter is not original. Perhaps Jaeger is the original for this car?
Anyway, I imagine this Lucas is set up correctly and is showing correct Amps. Which explains
sort of my problem. I have almost never seen the needle on the plus side. So I guess either
my generator is not working to charge the battery or something is sucking power from it.

Trike4 Avatar
Trike4 Marcus G
Brighton, Michigan, USA   USA
1963 Triumph TR4
1963 Triumph TR4 "Trike"
Tom,

Your ammeter is the correct gauge for your car and the manual is showing the older style. They function the same. The ammeter will show negative if you are using more amps than you are generating. Normal running without lights and heater wont use much amperage so you could probably drive around for a few days and not notice. The generator and voltage regulator function together so its hard to easily figure out which is at fault. In normal operation the regulator senses voltage, if it drops below about 14 volts it energizes the field windings in the generator more and more. Lets say you turn on the headlights, you would notice the needle on the ammeter move to the negative (meaning you are drawing from the battery). The regulator will command more voltage from the generator and you will see the needle move back towards charge + and then stabilize soon after at the middle.
Other than occasional twitches when turning things on or off you shouln't see much needle movement meaning the generator is supplying all the voltage and the battery is charged.

I would charge the battery and then do some testing.

Easy generator test you can do
[url=http://]Testing the voltage regulator[/url]

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tomster Avatar
tomster Tom Dunbar
Annapolis, Maryland, USA   USA
Thanks Marcus - perfect! I was actually already researching those videos.
I'll try to get in the habit and do some more upfront troubleshooting before popping off on this forum.

I'm already charging the battery and will run those tests tomorrow (day off - holiday). Hope I can get
back on the road. Heck, I'll drive it gingerly regardless and just trickle charge the battery if I don't solve
it quickly.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
I didn't watch the Moss videos, but they have said things in the past that I rather strongly disagree with. So my suggestion is to follow the Lucas tests instead. If you follow the steps in the order given, it pretty clearly indicates where the immediate problem lies.
https://drive.google.com/file/d/0B2H2NJt34OffNTc3ODkwYzAtYjRlYS00NDNmLWI0YTYtNjY5ZjQxZTA2NGFm/view?usp=drivesdk

Then after any repair or adjustment, run the entire test again. Not at all unusual for one fault to lead to another, so, for example, a misadjusted control.box may cause the generator to fail.

Worth noting that the generator doesn't do much at idle, it normally will not keep up with headlights and so on. But it should catch up eventually at higher rpm.

Current limiting is an important function of the control box. Without it, the generator will happily generate enough to overheat and ruin itself. So don't be tempted (as I was) to turn it up higher to get more charge out of it. Also, if the ammeter reads more than 20 amps charge for more than a minute or two right after a cold start, stop immediately and address the problem before going on. Its far better to limp home with the generator disconnected (if necessary) than take a chance on burning up the generator or battery.

Last time it happened to me, the problem was a bad connection inside the field relay.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

tomster Avatar
tomster Tom Dunbar
Annapolis, Maryland, USA   USA
Thanks for the link Randall. I'll take a look at that in the morning. Nice logical flow to that testing. thumbs up

ducbsa Bruce Metcalf
Berryville, Virginia, USA   USA
Apologies if this was already covered in the tests, but ammeters can be hooked up backwards. The easiest way to tell is which way the needle goes when you turn the headlights on. That way is obviously discharge/negative. To fix, just reverse the wires going to the terminal posts.

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tomster Avatar
tomster Tom Dunbar
Annapolis, Maryland, USA   USA
Testing in process right now. I did the first Lucas test by connecting the black test lead to the "D" terminal on the Generator which I guessed is the fatter one that is slanted and the positive lead to the frame. I assumed the thiner one straight up and down is the "F". I had my son sit in the car and rev it up to 3000 RPMs as instructed and I read .25 on the voltmeter (near zero). So based on that I think I'm done but I'm going to check my procedure with my Engineer neighbor when he gets home.

So my next thought is if it is the generator then I'm thinking I'd go ahead and just buy another one and re-build this one as a backup.
Any thoughts or preferred places to buy a generator? Looks like one can be had for $90 or so.

Thanks for all the help Marcus, Randall & Bruce.

PS. Today I drove it off the battery anyhoot!

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Just to be certain, I might try repolarizing the generator and trying that step again. Just momentarily connect 'F' to the battery (engine need not be running). If that doesn't improve the situation, then I agree the armature is probably shot (very possibly from overheating).

Sorry, no help on where to buy. "Back when" I bought from Bap-Geon, but they're gone now and I didn't like the way they refused to differentiate between a C39 and a C40. (Early vs Late TR3A; but Lucas said not to mix control boxes between the two models.) TRF appears to have the same problem; but they also claim to have found some new C40 with the original aluminum end plates.

If I hadn't decided to convert to an alternator, I probably would have found a local "auto electric" shop to rebuild my original generator for me.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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Trike4 Avatar
Trike4 Marcus G
Brighton, Michigan, USA   USA
1963 Triumph TR4
1963 Triumph TR4 "Trike"
Besides re-polarizing you may want to do that simple test MOSS suggests where you run the generator as a motor. It would be a bummer to buy another generator only to find something is wrong with a wire or the volt regulator.
I may have an extra generator for your year TR4

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Running as a motor with no load proves almost nothing at all; I have seen shorted (from obvious overheating, thrown solder and everything) armatures that would work enough to spin but no way generate as it should.

And the 2 volt test bypasses essentially everything else, it only looks at what the armature can generate with the residual magnetism field from the iron housing. It can't be affected by a bad control box or wiring (since neither is even in the circuit at that point).



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

tomster Avatar
tomster Tom Dunbar
Annapolis, Maryland, USA   USA
So if I understand Randall correctly. Re-polarizing could actually correct the situation? (sorry, I'm in learning mode)

And Marcus if I understand what you are saying - simply replacing the generator may not cure the situation as there are wires and
a voltage regulator between that and the battery, so test everything to completion up to the battery. Basically, I think my neighbor
was telling me the same thing. Test the wires separately etc.

I did like that Moss test showing the generator running, real evidence as opposed to a number on a meter (which may or may not be set up correctly).

oldhokie Gold Member DAN ALLEN
Myersville, Maryland, USA   USA
In reply to # 1497182 by tomster Testing in process right now. I did the first Lucas test by connecting the black test lead to the "D" terminal on the Generator which I guessed is the fatter one that is slanted and the positive lead to the frame. I assumed the thiner one straight up and down is the "F". I had my son sit in the car and rev it up to 3000 RPMs as instructed and I read .25 on the voltmeter (near zero). So based on that I think I'm done but I'm going to check my procedure with my Engineer neighbor when he gets home.

So my next thought is if it is the generator then I'm thinking I'd go ahead and just buy another one and re-build this one as a backup.
Any thoughts or preferred places to buy a generator? Looks like one can be had for $90 or so.

Thanks for all the help Marcus, Randall & Bruce.

PS. Today I drove it off the battery anyhoot!

A simple generator test is to full field it. Not familiar with the innards of TR4 generators but this should work:

  1. Start engine and set to about 1500 RPM
  2. If positive ground system BRIEFLY short generator field terminal to ground and observe ammeter
  3. if negative ground system BRIEFLY jumper field terminal to positive post on battery and observe ammeter

When full fielded the generator will produce maximum output. If you have full field output look elsewhere for your problem. If no output generator is likely bad.

Dan


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tomster Avatar
tomster Tom Dunbar
Annapolis, Maryland, USA   USA
But Randall the 2 - 4 V test from Lucas was only the first step.
Upon completion of that you move to the next step. Like a decision tree to isolate the exact problem.
At least that is my understanding.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1497241 by tomster But Randall the 2 - 4 V test from Lucas was only the first step.
Upon completion of that you move to the next step. Like a decision tree to isolate the exact problem.
At least that is my understanding.
I guess you can put it that way, but the next step with your result is to examine the brushes and, if they are physically OK, replace the armature. Then you start the entire sequence over again.

You only proceed to the next test when this test produces 2-4 volts.

There might be other problems, like the control box or wires; but it has to pass this test first before the other tests are meaningful.

Repolarizing is not likely to solve the problem; I've never seen a generator lose it so completely that it wouldn't do the 2 volt thing. But it's theoretically possible; and easy to try.

Just for a bit of background; when you first start the engine, the generator has no field current (meaning the field coils aren't generating a magnetic field). But that tiny bit of power created by the armature spinning in the weak field stored in the iron housing gets fed to the field coils; which produces a stronger magnetic field, which in turn generates more power and so on. Only takes a fraction of a second for all this to happen, but the essential first element is getting some voltage without field current. Once the voltage reaches 12v or so, the cutout relay closes, connecting the armature to the battery and charging can begin. The voltage coming up is also what turns out the red light on the dash.

"Repolarizing" is just refreshing that weak magnetic field stored in the iron housing. The polarity of that field is also what happens to determine if the generator produces a positive voltage (for negative ground cars) or negative voltage (for positive ground cars), hence the name.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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