Ammeter behavior

[Member 10617]

I thought I could easily get an answer to this question among my friends here in my town, but I've had no luck. Seems it may be more complicated than I thought. So I throw it out to you on the forum.

When I, in my 58 TR3, reach 2000 RPM and above -- that is, when I accelerate or am driving at 45-50 mph -- the ammeter needle goes almost to the maximum (30+) and stays there. When I slow down and when I stop, it drops immediately to the midpoint ("0").

My question is: shouldn't the ammeter settle down remain at somewhere around "0" or between "0" and 30+ once I have begun driving the car and the battery has been charged up after my initial start?

I checked recently and was told that the battery is in good shape. So I don't think that is the source of the problem.

The voltage regulator and the generator are both brand new.

Does the ammeter indicate that the battery is being over-charged?

 

[Geo Hahn]

...My question is: shouldn't the ammeter settle down remain at somewhere around "0" or between "0" and 30+ once I have begun driving the car and the battery has been charged up after my initial start?...

Yes. I would start by checking all connections (including grounds), especially those on the back of the generator as they live in a hot oily area. Next stop would be the battery posts. Then on from there.

Beyond that, I never assume just because a part is new that it can't be a problem.

 

[Member 10617]

The generator is brand new -- just been replaced. Another one -- also new -- was fried by a problem with (?) the voltage regulator. (In fact, three new voltage regulators had to be installed before one worked properly.) All this was done by mechanics who work almost exclusively on British sports cars, so I have to assume they installed it properly (but I will take it back and check it out). Also, when they did all this work, about three weeks ago, they checked the battery, cleaned the posts, tightened the cables, etc.

Does the fact that the ammeter returns to "0" when the engine is running at below 2000 RPM mean anything?

 

[TR3driver]

+30 on the ammeter doesn't necessarily mean the battery is being overcharged ... but it sure DOES indicate that the regulator is not working properly! This can overheat and kill the generator in fairly short order (it's only rated for 19 amps continuous, or 22 if it has been upgraded with the almost identical TR4 unit); so I would suggest dealing with it sooner rather than later.

There is a small chance that the problem is not actually inside the control box, so I would first try removing the wire from the 'F' terminal on the control box (engine not running) and then start the engine. If the red light stays on and the ammeter stays just slightly south of zero, then the control box is either defective, misadjusted, or not wired properly. If it still charges with the wire off, then either the two wires to the generator are shorted together somehow, or there is a short inside the generator.

There is a fairly good guide to testing available at
https://tinyurl.com/37voevm
(although I think you may need to create an account with Gmail first to download it, and you will need a copy of Adobe Acrobat Reader.)

 

[Member 10617]

Randall,

Many thanks. What you have said about the regulator not working properly sounds like what happened a few weeks ago when it killed the generator. The mystery is that the mechanics installed a new regulator and a new generator after that incident. And now the problem seems to be happening again. I'll take it in as soon as possible and have it worked on as I am not savy enough to deal with these matters.

 

[TR3driver]

I dunno ... seems to me that you're at least savvy enough to know there is a problem; which is apparently better than the mechanics you've been going to!

I don't know, but it would not surprise me if new control boxes still need to be adjusted; while most mechanics seem to have a "replace things until it works" mindset.

 

[Member 10617]

Randall,

You are right: my experience is that many mechanics are better at replacing things than repairing things. Not much I can do about that, however, regrettably. In my next life I think I'll skip grad school and go to auto mechanics school -- much more satisfying and more useful! Perhaps even better financially. Ha, ha.

You are also right that even though I don't know how to fix these cars, I do have a sense of what seems to be working and not working. I think it is nothing more than "common sense" at work. At any rate, it is my only defense. And it has saved me several times from breakdowns along the side of the road. The problem is that when an amateur like me says to a professional, "I don't know... but I think something is not quite right," the professional initially doesn't give it much credence. They become a bit, let's say "defensive."

Fortunately, I have a shop that tolerates my misgivings and checks out my concerns. Nine times out of ten, it turns out there IS a problem.

I have mentioned this before, but I'll mention it again. The few repair manuals available for the TR3 assume that the user is pretty knowledgeable. Anything that is "basic" is not explained or illustrated. If there were enough market for it, what we need is a "Triumphs for Dummies" book, to help us rank beginners. (For example, just try to find instructions on how to set something as simple as the idle speed in a TR3!!!) -- Of course, I am also aware of what Lincoln once said: "For every problem there is a simple solution ... and it is usually wrong."

The payoff, of course, is that rare time that you are humming down the road in you car enjoying the countryside, and nothing breaks down, falls off, blows up, or melts down. I give thanks for small miracles.

 

[Andrew Mace]

...If there were enough market for it, what we need is a "Triumphs for Dummies" book, to help us rank beginners.....

Well, it was out there in 1968:

<span style="font-style: italic">How to Repair Your Foreign Car: A Guide for the Beginner, Your Wife, and the Mechanically Inept</span> , by Dick O'Kane. You might still find it in a public library, or you can try to find a used copy online @ Amazon or similar (they seem to be getting expensive, though)!

 

[Geo Hahn]

...If there were enough market for it, what we need is a "Triumphs for Dummies" book, to help us rank beginners...

Here's another one, from Readers Digest. Sort of a companion to their Home Repair book that saved my bacon more than a few times:

With 480 pp it is fairly comprehensive. Published in 1981 when most older cars still had carburators & no computers so the fundamentals are in there.

My niece actually works for the publisher of "_______ for Dummies", I may suggest a title though it would probably have to be classic cars in general (not merely Triumph or British) to have wide appeal. I already suggested to her "Ventriloquism for Dummies" and "Crash Testing for Dummies" and she didn't think much of those ideas.

 

[LBCs_since_1988]

Just a suggestion: Don't rely on the original Ammeter for diagnostics. Get a proper multi-meter.

 

[Member 10617]

Thanks for the leads to the manuals. I'll look around to see if the HOW TO REPAIR YOUR FOREIGN CAR is still available somewhere.

As for the caution not to rely on the original Ammeter, I have to agree.

Just to finish off my story, here is the latest. Perhaps you can make some sense of it.

I drove to the shop this morning that works on my car. On the way, the ammeter continued to do its thing: at 2000 RPM or higher, it rose to about 30+ and remained there (dropping only when I stopped the car). Since I was on a highway, I switched into overdrive and, presto, the ammeter fell to between "0" and 30+, and remained there! After a few miles I switched off the overdrive to see what would happen and, presto, it remained at the halfway point and did not rise to 30+.

At the shop the owner said, "You cannot rely on these old Lucas ammeters." (Just what Aaron has posted.) He said that the problem might be with the spring in the ammeter, or any number of other things. He attached an electronic device to my car and he and several others watched the read-outs as they revved up the engine and ran it through its paces. Their conclusion: the electronics of the car were operating as they should. They also double checked the battery and found that it was good.

Relieved and reassured, I headed home. But on the way, the ammeter once again did all of its tricks. I decided to stop worrying about it and enjoy the ride.

Perhaps I need to take the LUCAS label off my battery. It came with the car, and so, it seems, did the "Curse of Lucas."

The shop owner was surprised to learn that I have been driving my car the past two days as the temperature has reached 100+. He said -- half seriously -- that all the TR3s he knew of would probably overheat in such heat. I told him that not only did my car not overheat, but that the temperature gauge (recently entirely rebuilt) registered at the mark BELOW 185, and remained there. He said I must have the only TR3 on this planet that runs that cool in such heat. My thought: life has its compensations, even when it comes to these cars.

 

[TR3driver]

For LBC electrical work for the complete novice, I would recommend Dan Master's manual. Unfortunately, AFAIK, he never got around to writing the TR2-4 version; but the existing TR250-TR6 version, combined with a diagram that matches your car, should get you a long way down the road. It's not rocket science after all (and many of us started without any sort of manual, let alone resources like BCF).

Just out of curiosity, what was the ammeter doing while the shop had their ammeter connected?

BTW, my TR3A wouldn't run below 185, as I had a 185 thermostat in it. But it also would not overheat even in 115F ambient ... the driver overheated first!

Haven't had a chance to drive the 'project' TR3 in such temperatures yet, but I'm expecting similar performance. First I need to do something about the temp gauge, the aftermarket gauge I moved over from the 3A is starting to act up.

 

[cheseroo]

I don't believe any hands on car person's library is complete without this book. It's the most common sense approach to auto repair I've ever read. Yes it's for a VW but how many manuals out there explain how you can use a rock to fix something when you are broken down at the side of the road? Every other manual I've read takes the approach that you are fixing something in a shop with all the proper tools. This one approaches the repair with the perspective that you are broken down at the side of the road or have no money for special tools. I seem to recall it includes some rather interesting advice on things to do while waiting for the motor to cool down.

 

[LBCs_since_1988]

For what it's worth, the TR6 Voltmeter is MILES ahead in reliability than the early Ammeter. My Ammeter works just enough to let me know there is current flowing. At high-revs it reads ok.

I once read on a Mustang forum (I know, I know -it was just a Google serach!) that "their" Ammeter just bopped around aimlessly. Others chimed in and said "There's nothing wrong with it. They all work like that!"

Any run-of-the-mill voltmeter on the other hand seem to be very accurate.

 

[Member 10617]

The unit the shop guys attached was attached to the poles of the battery. At one point, they asked me to tell them what the ammeter was doing as they revved the engine. I looked and it was registering 30+.

BTW, what are the signs that a generator is malfunctioning or that a voltage regulator is malfunctioning.

I don't suspect I have a problem, but I want to be able to monitor them. from what has been said here, I cannot depend on the ammeter in these cars to diagnose any problems.

 

[TFB]

Ed,
Not exaclty sure how ammter is wired in tr3 but,generally they work and indicate current,amps,quanity and the direction.
Vintage generators are usually quite reliable ,thier main disadvantage is heavy,low output ,and worse output at low rpm.Plus you said you have 30+amps.
Most all charging problems are more likely related to the mechanical voltage regulator which has sloppy control at best,compared to electronic regulators.
So I will putting in a 3 wire alternator with internal regulator ,using my orig. regulator as a terminal blocK.
The other option,(seen on this list) is the electronic unit fit in the old mech. reg.
Have fun
Tom

 

[Member 10617]

Tom,

Many thanks.

My car has a second brand new generator, a brand new alternator, and a third brand new voltage regulator -- all within a few months. I describe them this way because a few weeks ago, as far as the mechanics at my shop can tell, the new voltage regulator that was recently installed in my car malfunctioned and killed my new generator. The mechanics went through two other new regulators before they found one that was not defective and finally got the system working again, and they replaced the "fried" generator.

The system seems to be working OK since then, but I have had this question about the ammeter reading high when the engine hits 2000 rpm or higher. I had things checked out again yesterday, and the mechanics said it is probably a faulty ammeter.

I have suggested putting in a solid state voltage regulator, but the shop guys don't want to do it because they trust the electronic units even less than the standard units.

If I have any more trouble with the regulator, I think I'll argue for the solid state regulator.

 

[RJS]

Hi,

(Silly) question. If the TR3 generator is only rated for 19 amps continuous output, is it actually possible for it to max out and pin the ammeter at 30+ amps?

If Yes, then I learned something new. If No, then I would be very suspicious of the ammeter displaying 30+ amps and would first look to diagnose the ammeter.

Bob

 

[TR3driver]

Not a silly question, Bob. The answer is Yes, at higher rpm the generator (like most DC generators) is quite capable of putting out substantially more than it's rated current. This is why one of the duties of the control box is to limit generator current as well as voltage. A healthy system will actually reach close to 30 amps if you rev the engine right after a cold start; but should quickly regulate back down to 20 amps or so.

Generators definitely fall into the "dancing bear" category IMO : What is surprising is not how well they dance, but that they dance at all.

I'm still dubious about the ammeter reading high; but if that is the case, I would want to replace or repair it. They very rarely fail (all of my originals still work fine) and so used originals should be relatively inexpensive. Or any of the gauge restorers (Mo-Ma, N.Hollywood Speedo, etc.) should be able to repair it for less than the price of another generator.

 

[TR3driver]

from what has been said here, I cannot depend on the ammeter in these cars to diagnose any problems.

Well, I guess that puts me in the minority (a common situation). Compared to the voltmeter in both of my Stags (which is basically identical to the later TR6 voltmeter), the TR3 ammeter is a paragon of simplicity, reliability and accuracy.

The voltmeter reading is affected by any voltage drop through the wiring or ignition switch; the ammeter always reads actual current. (Of course the current may be affected by voltage drop in the wiring, but that is a different issue.) In addition, both Stag voltmeters are off by over a volt (more than the difference between charging and not charging). When I tried to calibrate one of them, I found that it's internals were so sloppily assembled that any minor shock (like setting the unit down on the bench) would change the calibration!

IMO the main reason ammeters get a bad rap is because they do indicate exactly what is happening, right now. Any changes are instantly reflected (including the regulator points opening and closing). Voltmeters (especially the type used on later Triumphs) give a much more smoothed indication of what happened in the past.

Just one example, a voltmeter will NEVER tell you if the current regulator is failed, as long as the voltage regulator is working. An ammeter will. A voltmeter will also not tell you that you've left the lights on, or that the brake lights are not working. The list goes on.

Yes, 50+ year old automotive gauges can have problems. But I would say that the ammeter is the most reliable one of the bunch, rather than the least.

And I guess I asked the question the wrong way, so I'll try the other way : What was the shop's ammeter indicating when your dash ammeter read +30?
Or did they not have an ammeter connected at all (to connect an ammeter requires opening the circuit, not just connecting to the battery posts) and assumed that since the voltage was within limits, all was well?