I've recently had two of the 20-0-20 Taiwan ammeter repops start an electrical fire (actually just a lot of smoke) under the dash of my '26 tudor. This last one ruined the switch wiring harness before I jerked the + battery cable off. Then, a friend and Model T restorer of excellent repute told me those cheap repops are all dangerous and I should get a slightly more expensive 30-0-30 Model A ammeter. It looks like Snyder's sells the 30-0-30 script ammeter but for the same $8.25 as the ones that started the smoking. I looked at our friend John Regan's Fun Project website but he hasn't reproduced the smaller ammeter. Has anyone else experienced the same calamity and can anyone offer a source of better quality ammeter?
My only comment is to make a practice of pulling the ground side of the battery first. That kills the battery power, and is safer than putting a wrench on the hot terminal, with possibility of getting wrench in contact with both hot terminal and chassis.
Tough luck on the ammeters.
my only comment is the importance of an NHRA style battery cutoff
I'd shop for an original.
There is a way to keep the ammeter out of the circuit until something better is found. Of course it does not read accurate but it sure shows a charge or discharge.
Think I read this in tinkerin Tips or some other 'get by' rag and actually did use it on a '25 years ago that when I rewired the spaghetti to new, the ammeter didn't work.
Take a decent size wire of 14 or 16 gauge, take ten wraps around a pencil and slide the pencil out. Clip the leads to fit and mount it across the two ammeter posts. Then slide the gen wire through the 'coil' produced and continuous. Now whenever the wire sees 'flow', induction has the ammeter point in the right direction.
If there is something here that later proved 'whacky' or 'unsafe', please advise...but it was published eons ago, I did try it and it worked on the '25 until I finally got around to getting another meter.
Since the major burn out was caused by a short to ground the attempt at induction would do nothing to have stopped that. Besides - an induction ammeter is made to operate by induction and you cannot convert an ordinary ammeter into an induction ammeter as Tinkering Tips suggests. I read that idea with amusement - waste of time. All that is being done is a much lower shunt resistance is being installed outside the ammeter but that is pure guesswork and I would strongly suggest you not do that. You will only make things more dangerous IMHO.
The small ammeters all come from the same source whether they are T or A and whether they are 20 or 30 amps.
There was an excellent source of these small ammeters some years ago but they sold for the unheard of sum of $12.95 each so of course they were ripe for a competing part at $8.95 and the good source stopped making them when everyone bought the junk at the cheaper price. When you see a "me too but cheaper" - remember that the original source may pull out and you may find that you screwed up by shopping price only. Your mileage may vary.
OK...thanks John I was just offering some old advice as a pass on, and if it is wrong or dangerous, last time I'll do that
Glad we have people like you who know right from wrong and not just lore or wives tales...
I would think their would be market for a quality built, small size ammeter as it could not only be used on 26-27 T's, but all Model As as well. The new ones are junk and usable originals are scarce.
There have been at least 12 garages burn in the last 12 years with a Model T lost. In each case, the Model T was never blamed. I have witnessed 3 fires and they were all caused by that cheap or an original 1926 style ammeter, due to the insulators loosening up from drying cardboard or the securing nut loosening from vibration. When that happens the terminal drops down enough to contact the case and that terminal is always hot, unless the battery is disconnected. I had that same problem with a Model A in 1956 and I believe those ammeters have caused a lot more fires than they have ever been given credit for to date.
Thanks to all for their input. A month ago Ralph taught me there was no 'p' in ammeter and today he taught me to pull off the ground battery cable first. John, theres a market here !! Put me down for 4 when you get tooled up . . . .and I expect to pick 'em up at Chickasha ;o) And thanks for confirming the problem with these later style ammeters. James, you really hit us with a power punch!! We hobbiests and T drivers need to be aware of that lurking tragedy. Even when I replace the switch wiring harness, I'm not re-connecting the battery or driving the tudor until I feel more confident with the fire safety. Think I'll go out and drive the '14 runabout and not worry about an ammeter - just watch that magnetometer peg at 30 volts . . .
Paul, like John said, there is a market as long as the price does not exceed $8.95 It's pretty typical of the hobby, most don't want to spend any money to make their car reliable, so they paper clip and rubber band it together and complain about how it is not reliable.
James, your input is very valuable!
I think your explanation of the old-ammeter problem is proof positive that a 25 or 30 amp fuse as close to the starter switch as possible, is an excellent idea.
I know that if the fuse blows the generator could be cooked, but there are two answers to that objection that come to mind: 1) Most folks start their T's on Battery, and if the fuse is blown it won't start, and 2) I'd rather lose a generator than the whole car and/or my garage to boot.
If you have a fuse on the generator field coils, you won't loose that either.
I was not aware of the problems that the ammeter has caused for the improved car. Perhaps the idea of some type of inductive meter could help solve some of the problems. If the wire that carried the current did not have any connections but rather a coil of wire wrapped around it, that would go a long way to solve some of the problems.
Automobiles did not always have a meter that was what it said. The 1963 Corvette had an ammeter reading on the face of the gage, but the wires behind it were 18 or 20 gauge.
Perhaps John or someone can come up with a meter that has a needle that swings both ways and gives an indication of charge or discharge. To set the third brush one could use a real ammeter installed temporary at the generator output to measure just for setting the third brush and promptly removed!
The meter on the dash would just be used to indicate if the system was charging or discharging.
What do the members think???
Ken - what fuse do you use on the field coils?
Yachts and other big boats use a system by which the main battery wire (not to the starter) runs through a corrugated metal strap, which has a known resistance at 12 volts. Then small wires, connected to both ends of this strap, feed a voltmeter on the dash that measures the voltage drop across the strap. The meter is marked in amps, and acts just like a feed-through ammeter in terms of what it tells the driver.
This also allows multiple ammeters, which is useful in a yacht that has an indoor control station as well as controls on the flying bridge.
That kind of system is probably what the 1963 Corvette had, as described by Arnie.
I suppose some variant of this system could be adapted for use in a T, but as stated before, the cost would probably be prohibitive.
Why would this meter be cost prohibitive. It seems like only voltage would go through it and would not need heavy wires for a 20 or more amps to go through it!
The first Mustangs with alternators used the resistance of the wiring harness main cable to the alternator as the ammeter "shunt" resistor. The ammeter was not calibrated in "amps" but just had some markings on it to indicate the amount of charge and the driver would simply note the correct reading after owning the car for awhile I guess. It is just a normal ammeter with a remote "shunt" resistor. In the T ammeters both large and small the shunt is inside the meter. In manufacturing an ammeter for the T it really doesn't help much to hook the ammeter up to a remote shunt. With the T guys being such tinkerers it would be very easy to damage such a meter since the shunt inside the meter is also the device to protect the movement. With remote shunt an ammeter is pretty easy to toast by one simple wrong connection to its leads or a failure somewhere in a wiring connection. Most precision meter movements will reach full scale with .001 Amps flowing through the movement. That means on a T that 19.999 Amps is flowing through the shunt.
Those of you who have a VR on your generator really don't have to worry about your generator being damaged if a main fuse blows since the VR has a circuit in it to watch for a battery disconnection and shut down the generator quickly when that happens. In any event if you have a main fuse at the starter switch in the heavy yellow wire then you cannot possibly be better off in any way by not having that fuse blow since your wiring is in danger of starting a fire when that 25 amp main fuse blows. I strongly recommend that one single fuse (25 amps - no bigger - no smaller) but just for the record I also would recommend the generator field fuse if you don't have a VR on your generator. More fuses than the one main fuse is just more potential loose connections and doesn't add any real protection over the one main fuse since a short anywhere in the car wiring should take out that main fuse and there just isn't that much wiring to need more fuses IMHO.
Henry didn't furnish "fuses" on his Model T s. Inquiring minds demand decent ammeters that won't burn their treasure down. The 'technical expert' at the vendor that sold me these (2) shoddy ammeters gave an apology for possible defectiveness of another item I purchased: F11 Motocraft spark plugs. Haven't had any problem with them. Our vendors should remove these sorry ammeters from their inventory and demand better quality.
Does any one rebuild ammeters? would it be hard to do and not worth the cost to do it? John
The guru of switch plates, Ben Martin, will rebuild the Improved car (small) ammeter.
He will use the new reproduction Model A version guts, which are 0-30 amp, but use the paperboard face of the original Model T small ammeter, so it will look authentic.
Has done several for me, and they work great, along with the Fun Projects VR, that is a must
Original '26-'27 Model T ammeter, just supply a good core, this one was redone with new innards by Ben Martin.
Ok this could be dangerous--a mechanical guy talking about an electrical item!
I have taken a pointer type volt meter and connected it polarity wise backwards. When I did this the needle wanted to go below zero.
Now if this volt meter was constructed with the needle in the center position for "0" volts, then the needle indicator would tell me which way the voltage was higher. In other words, the voltmeter connected in such a way, if the circuit was charging (higher voltage because of generator output) the needle would go one way and if the engine was off and the headlights were on the needle would go the other way.
I guess I keep thinking about the "ammeter" on the 1963 Corvette that was really measuring voltage across two points. The end result was very little current needed to pass through the meter. With the current (pun intended) Model T ammeter a lot of current is directed to the meter and an internal shunt takes most of it, but the problem remains, the large current is fed to the back of the meter as opposed to the Corvette meter that had thin wires behind it and little current fed to the back of the meter.
The idea would be to connect the large current carrying wires together with solder and shrink sleeve to prevent that dreaded "connection problem" with the T and then simulate current indication with a voltmeter with low current going to that instrument.
Again I do not know if this is electrically possible (remember a mechanical guy!), but I keep thinking that they somehow did it in the 1963 Corvette!
For your info ALL mechanical meters that measure anything doing with DC are in fact DC current meters!! A voltmeter is nothing more than a DC current meter with a resistance in series with it. A 20-0-20 ammeter is nothing more than a movement that has its resting pointer located mid scale as you noticed. All such meters go below zero when connected up "backwards" and generally speaking there is little or no extra charge when buying a meter movement that is 0-20 amps or 10-0-10 amps since it only involves moving the pointer to the center of the scale which is basically like adjusting the "zero" setting mechanically with the zero setting screw located on most meters. The basic movement of such a meter has a sensitivity rating which defines how much actual current it takes to make the meter deflect to full scale. Probably the most common movement is a so called "one mil movement" or a movement that requires 1 milliamp of current to move it to full scale. A decent lab grade movement might be a 100 micro amp movement an old test meter I have here has a 50 micro amp movement. By changing the face of the meter to a new range and adjusting the series resistor you can make a 1 volt meter into a 100 volt meter for a few pennies. You can put a very low resistance in parallel with the same meter movement and make a 30 amp ammeter out of the exact same meter movement. The zero center type can have their scale changed too but it is not quite so simple to move the zero center meter to make it then read from zero to a high value with the zero now at the left side since that involves a mechanical change to the movement but it is usually rather simple to do by the movement manufacturing company.
In other words your explanation of what you think would solve the ammeter issue is already the "ordinary" way of doing it since I repeat - ALL DC meter movements are in fact operating on DC current only.
AC ammeters are somewhat different but still operate on current rather than voltage.
Way more than you wanted to know but know that it is not simple to make the small meter mainly because Ford began to use the cheapest and worst movement he could find and left no room in there to make it better by putting in a better movement. The larger meter had room in it for a better movement so I was able to make a decent ammeter for you guys that is more accurate than original and more "damped" so you can actually read it ha ha. For a small meter it is not likely that one could make it much better than original Ford but just about anything could be much better than the current repro item. Using quality parts for the insulating washers and such would likely make it at least a bit safer but nothing will make things better and safer than having that one main fuse in there that Ford omitted.
When it comes to buying stuff for your T you need to ask yourself who designed it and does that person or organization have the expertise to have known what they were doing. There are some very clever craftsmen out there that can make things that look good but are they designed properly? I plead with vendors to get the factory drawings and stick to them at every detail possible unless they are more qualified than the drawing and know that their "shortcut" will in fact work OK or better.
I can't speak for a lot of technologies but I can tell you that there are a ton of guys in the aisles at Hershey that are hawking electronic things that are NOT good ideas and certainly not engineered properly. What often happens is that some guy hooks something up that he adapted from a modern car and it seemed to work OK so he and his buddy started making kits and selling them without knowing any of the real consequences of their actions since they had no electrical engineering background. Would you buy a scuba tank designed by a guy who doesn't know how to swim? Why don't you ask him at least if he CAN swim. If electrical - ask who designed it? Does that designer have the credentials to sign off on the whole idea as OK? Has it had peer review? Who is the peer and what are his/her credentials? If it can burn up your car - it is at least worth asking and if you have zero electrical background then all the more reason to be asking. Don't collect opinions - get facts. When I buy anything electrical for my house - I look for the UL label on it or I don't plug it in. Be a skeptic about anything that is not original Ford parts for the T.
I have a number of originals which while I haven't checked them, they all return to zero when shaked. I plan to have the rims renickeled and then will offer them for sale.
Again I am not an electrical engineer so that is why I am asking these questions.
The point I am trying to make is that GM in their "ammeter" (wiring dia shows a typical voltage measurement hook up) in the 1963 Corvette (I believe the scale was plus or minus 30A) did not have any large diameter wires in the back of the meter. In fact it had two spade terminals, I believe, positioned at 90 degrees when looking at the back of the meter (sort of like a T formation, and a plastic connector held the female terminals in the wiring harness). The Model T meter has most of the current going to the gage and from the gage. I understand that the internal shunt takes most of the current. This is different than the Corvette gage that did not have this large current flow to and from the gage.
So is the problem the sensitivity one can get in a small round gage package? Unfortunately I do not remember the physical diameter of the Corvette gage. It was also a 12 DC application but perhaps that is not critical.
My position is if the present wiring for the ammeter on a Model T Ford could be spliced together where it normally connects to the ammeter this would be one less connection where an open circuit could occur and thus one less chance that the generator would run wild and die!
If one then substituted a "voltmeter" reading amps one could still get an idea of which way the current is flowing without putting the generator at risk of an open circuit.
Does this make sense or am I all wet?
P.S. I know that John's regulator protects the generator on open circuit, and that is a great feature, but I am thinking of others who run the stock set-up. If this change was possible the outward appearance would not change, just how the current indication was made!
Ok, I have a question to Arnie's question. If we initially set the output of the generator and then let it run like it should and we really only care about whether or not it charges because the meter is so poorly damped it is difficult to read, why not just use an idiot light like new cars?
Exactly my point. With the ammeter wires that go to the back of the ammeter soldered together, it would eliminate the possible open circuit there. Your suggestion of an idiot light is similiar to mine, except it would look more normal with the wiggle of some "gage"! That wiggle might not be real accurate but would indicate charge or discharge!
Reread my post. I answered your questions but perhaps it just isn't something I can convey to you. The short answer is that you are making a very complicated issue and not helping much. A corvette and other modern cars do your method (which is their method) because they have very very high charge current capability from the source (typically an alternator or high current generator) and the wire size needed to handle the current is way heavier than #12 which is all you need for a T. Their method is not preferred if you consider the plight of the meter movement wires that might get crossed up but since the charging current in those vehicles is way beyond 40 amps - they have no real choice. I simply can't explain it any other way than stated. You simply don't understand that the shunt inside the small meter really is NOT the problem at all. Inside or outside it makes no real difference since it isn't huge. There is no room inside the small T meter for a D'arsonval movement whether the shunt is in there or not.
Reread my post. I answered your questions but perhaps it just isn't something I can convey to you. The short answer is that you are making a very complicated issue. A corvette and other modern cars do your method (which is their method) because they have very very high charge current capability from the source (typically an alternator or high current generator) and the wire size needed to handle the current is way heavier than #12 which is all you need for a T. Their method is not preferred if you consider the plight of the meter movement wires that might get crossed up but since the charging current in those vehicles is way beyond 40 amps - they have no real choice since they can't string super heavy cables to the dash and back. I simply can't explain it any other way than I stated. Please understand that the shunt inside the small meter really is NOT the problem at all. Inside or outside it makes no real difference since it isn't huge. There is no room inside the small T meter for a D'arsonval (good and accurate) movement whether the shunt is in there or not.
Why on earth not just fix the shorting problem at its source namely ask the vendor who makes the meter to please spend $0.15 and install hard fiber shoulder washers on his ammeter. It really can't be done any better or simpler than just making the meter correctly. It isn't rocket science and a 20-0-20 is not a meter that needs a remote shunt since #12 wire just isn't that big nor is the needed path of that wire difficult to traverse in either a T or A.