This is a 1915 car and it ran just fine on Mag or battery last fall. I took the engine apart this winter to check things out and freshen things up a bit. Started it up today for the first time and it runs just fine on the battery but when I switch it to Mag it dies AT ONCE --no sputter, no cough, no run--- just like I turned the ignition switch off.
I checked the output at the mag post and it reads 7 volts ac at idle and 12.5 volts when I rev it up. This 12.5 volts seems low but it should at least run , Am I right?
Took the cover off the switch and all looks well---- checked the switch function with a meter for continuity and all seems to work fine.
Looking for ideas on what to do next. Thanks. Joe
Assuming your mag readings were taken in the correct manner they reflect a weak magneto.
Ron the. Coilman
Do a search on the John Regan Magneto Test. Essentially, you make your voltage readings in parallel with an 1156 light bulb to give the magneto a load.
You said you took the engine apart. Did you install a new coil ring? Did you set the proper coil ring clearance? Did you check for crankshaft end play? Could you have damaged the coil ring? A short to ground part way around will result in a reduced voltage as current will still be generated in the coils between the short and the output terminal.
Are you using an analog voltmeter to take your magneto output measurements?
I've heard an analog voltmeter will kill a mag. Always good info on the forum!!
Here is the image and words that go with it:
A couple of questions:
1. What would happen if one were to measure directly from the magneto post to ground, without the lightbulb?
2. Is this measurement made with the engine running on battery or on magneto?
You do the test with the car running on BAT. The light bulb simulates the load of the coil. Measuring the voltage without a load does not tell you how the mag will work in actual use.
Read Ron P's post at:
Tim, use an analog meter. The meter will not damage the mag... unless you connect the mag to battery with the meter.
Joseph, did you paint your mag ring? It has to have a good ground to the engine to work.
Did you recharge your magnets when the engine was apart? If not, it isn't too late to charge them with the engine in the car. I do it that way using my AC/DC arc welder set to DC at the highest setting, 80 amps I think. It only puts out about 50 VDC. Years ago I posted the way I do this... same way Fahnestock said to do it except instead of 3 12V batteries I use the welder. After setting crankshaft position with a magnetic compass I hook it all up and leave the circuit open with two stripped end copper wires. Then whilst looking away I strike and release the wires to make a flash. One is all you need so I do it 4 or 5 times. When you set up to charge or if you build a charger you don't want to put a switch in there, even a blade switch will let you leave the current going too long. If the switch welds closed due to arcing then your goose (er, your mag) may be cooked. You don't want to heat things up.
Think of your mag as a light bulb (or if your'e old enough a flash bulb!). The longer it is turned on the brighter it glows and the hotter it gets! You don't want it to get hot or glow... this can lead to a burnt out mag, or fire, or worse (ie: brown shorts). You only want to it!
Remember that you create magnetism in the magnets only by rapid build-up or rapid collapse of the magnetic field. So the time the current is on does nothing but create heat, the work is done as it turns on and turns off.
Just in case, after reading the above suggestions, it turns out you have a weak magneto and want to do an "in car" recharge of the magnets, follow the below diagrams:
Mag Recharge instrts BEST.docx (13.5 k)
Bob, your chart has a major error. That 1 3/4th inch line should end or go to the center of the compass exactly under the needle post center.
You can see with that measurement shown, the size of the compass dial will create a major error between a 1 inch diameter and a 2 1/2 inch diameter compass dial.
If you take the same measurement on a Hand Crank Coil Tester, you will recognize and understand the error.
The HCCT Mag Post is normally positioned on the bottom, but it is still in the center of the two adjacent coils and you can find that center on top, without the post and then measure to the center of the two adjacent magnets, which should be positioned over the coil post for this test.
If the spark plugs are removed, the transmission placed in neutral and a rear wheel is jacked up, then the motor will turn very freely and the compass is not required, as the magnets will align themselves, only because unlike poles attract each other.
If you allow the magnets will align themselves you may be right 1/2 the time. There is no way to tell if the north or south pole is lined up. The mag plate has no north or south pole so it attracts either pole of the magnets. Try it on your HCCT and you will see.
Here is an update:
I ran the John Reagan bulb test ---low ldle produced a dim bulb and 6 volts AC. Reved up engine produced a bright bulb and 10.5 volts AC. Yes, I am using an antilog meter with a needle and a scale.
I agree that my mag is weaker than it should be and I need to address that issue but shouldn't it still run under the existing conditions??
I may be wrong but the root cause seems to be something elce.
To answer some of the other questions: I did not paint the mag ring and did not recharge the coils but only checked their strength by lifting a weight and they seemed strong. And sense the mag worked well before, I decided not to fix it.
Crank shaft end play now at .003 inches
Thanks for ideas but I am stumped on this one. More input please. Joe
Did you visually inspect the mag ring for damage? Did you replace the mag ring? A question for the rest (I suppose I could look up the answer for this one but)typically what can he expect the voltage to be?
Your magneto is very weak and will not properly operate coils.
Ron the Coilman
What is the gap between the mag plate and magnets? If you changed the crank end play that would have an effect on the gap. If your gap is too much, that would decrease the mag oupput.
I used the same method that Bob Bishop showed on one of my Ts the other day. Except that I didn't want to burn up one of my mag posts so I held a bolt in my jumper cable directly to the blob on top of the field coil. I then checked with an old mag tester and it showed good. I drove the T to Estes twice about a 70 mile round trip. It seems to be working OK.
I believe that the green bible (manual) shows a MAGNETOMETER directly on the magnets. I checked my magnets and another transmission magnets with a new magnetometer and both transmissions showed very good. but neither one lasted very long so I won't be trusting a Magnetometer again. Always before I got this Magnetometer I just used weights to test the Magnets, I think I will go back to that.
Joseph, I had a similar problem several years ago before I rebuilt my mag. The car ran pretty well for years but I decided to check my coils to make sure I was getting everything I could from them. I reset the coils to exactly 1.2. Cranked the engine and it fired on the first crank. I reached in and set it to mag. It was like I turned the switch off. After checking everything I could think of I remembered an old saying, "when something goes wrong, check on what you did last". I remembered that the coils were set very low. I reset them to about 1.0 and was able to keep it running but not well. I reset the coils to .8 and it was as smooth as silk. I know I did not have the power that I should but it got me there and back every time. I since have rebuilt the mag. Did you by chance adjust your coils when you "tuned up"?
28-30 volts is possible.
I was about to ask the same question, what is the gap.
I had a nut vibrate loose in the switch of my 1913 and fry the magnet charge after shorting the mag to battery. Last weekend I zapped the mag with my arc welder. It is running strong again at about 25 VAC. This charge should last years, but no matter it only takes minutes to repeat the recharge if it doesn't.
If your mag is weak because there is a short to ground somewhere on the mag then a recharge won't do it. I've heard people say that you can burn out a short by zapping the mag. This is the flashbulb kind of thing and I wouldn't plan on trying to do that (think fire or just plain ruining the mag). So I would take five minutes and re-charge it. If it doesn't charge up then you have a bigger problem and need to fix it next time you have the engine apart.
If 6 volts will ruin the magnet charge, why does it take 36 volts to put it back?
Thanks Hal. I recall seeing those kind of voltages on my sedan (28-30V) the one time I checked it but was starting to doubt myself.
James.......it takes a lot of soup to shake up a magnet.
It's not so much a voltage thing as a current thing.
If you to deliver equivalent current at 6 volts it won't pack the punch.
But at 36 volts with equivalent current the windings are getting 6 times the jolt.
Mind you it takes only a few quick jolts to "shock" the magnets into shape.
Anything more and you risk burning up the coils.
Well, based on all the good input, I decided to bite the bullet and go the safest route. My friend Carl Coggins showed up about noon and by 4:30 PM we had the engine out of the car and disassembled and the mag ring shipped to Snyder's so they can send me a rebuilt one. We also recharged all the magnets and now they all easily lift a 2 pound weight.
We used a set of charging coils they we had previously built and my DC welder to ZAP them--- made a big difference.
Thanks everyone for the advice-----I must admit however, that I do not understand why it would not run on Mag with 10 volts and a bright light with using the 1156 bulb test. Joe
Carl Coggins,Sanford's Best! Bud in Wheeler.