I have a 22 with starter/generator. Noticed today I have a short somewhere. Battery dead. Hooking up new battery noticed sparking. Definite drain with nothing on.
My question: I am planning on a small run with friends today. If I can't find the short, is it ok to run the car with the battery disconnected. Mag works good.
Don't want to hurt the generator.
Either remove the generator and install a block off plate or short the generator + terminal to ground.
I should continue that I am running a fun projects regulator, not a cutout.
Same answer applies.
I'm not suggesting that Royce is wrong, but I would love an explanation of why you would need to ground the positive terminal of the generator. There are no transistors to fry. Back in the '60s I did some auto racing - both roundy-round and drag racing. SOP was to disconnect the generator (we had a switch in the output circuit). By disconnecting the generator we took the generator load off of the engine and gained a horsepower or two. We never fried a generator. Is there something different about the T's charging system?
Does the middle paragraph below answer your question?
".... By John F. Regan on Sunday, August 04, 2013 - 12:00 am:
Well since not many generators survive being run open, I can't really give you a scientific answer but in general yes the higher the 3rd brush setting then the higher the initial output that starts the runaway. I think the diode you have is not a stud rectifier but somebody has pressed that "button" end of the diode into what appears to be a BRASS (Schrader?) Valve cap off a T wheel since they are rounded like that and also have a bit of a knurl at the exact spot I can see some in your picture. The only reason I can think they did that was that they had something that would accommodate the larger and longer brass housing. T guys are very very clever and resourceful. I suspect the guy had no way to fasten any electrical lead to the button end of the diode. Take a looksee at an old alternator diode and you will see that it has grooves to allow one end to be pressed into a plate with other diodes as part of the diode bank. It would not be possible to solder a wire onto that grooved end. What was the brass wheel valve cover thingee clamped or hooked to? I can't be sure of that being a valve cap but for sake of this post lets call it that so we both know what is being referred to.
If you have not actually witnessed a generator go up in smoke I don't think you would enjoy it much and not at all if it was your generator. The output of the T generator gets started by a small amount of residual magnetism in it that generates enough current to get a small amount of output from the armature. The 3rd brush connects to one end of one field winding and the other field is in series with the end of that second field going to ground. Thus what happens is that a small amount of output allows the 3rd brush to pick up a small amount of field current. The amount it picks up is indeed a function of where the third brush is at physically. Since a small amount of field current is more than it started with, the added field current then increases the armature current output. The larger armature current output causes even MORE FIELD CURRENT which in turn causes EVEN MORE ARMATURE CURRENT and the whole process becomes a runaway unless there is a load on the generator to drag away the armature current and prevent the runaway. Now clearly the higher the 3rd brush setting then the faster this all happens with the end result usually being the field winding is burned open if it is the only load. Sometimes if there is some load at the armature but not enough to hold back the runaway then the armature fails first since it is spinning and producing way too much power so solder gets tossed off the armature and that also ends the day for the generator.
There might be several reasons you got lucky. One I must suggest is that your diode was in fact shorted and then opened up much later. The the lead adjustment was way off then perhaps the generator was not only set very low but had the lead adjustment making the current even lower if it was on the wrong side of neutral. On that last supposition I must defer to those who work on generators since that condition may not be possible. Usually the runaway can happen so fast that there isn't time to see what happened. I am betting that the diode was shorted initially and saved things since if anything was open and your generator had continuity through the various circuits the thing would have had to overheat at least. Was there any evidence of oil on the armature since the brushes will typically ride up on top of the oil and this often causes even a good generator to stop charging? A new seal at the front of the generator and a thorough cleaning will fix that. I am starting to guess and in this case YOUR GUESS is as good as mine. I wouldn't worry too much about your good fortune since clearly you dodged a bullet if you survived a bout with the generator spinning with no load. Armatures can be rewound and field coils are being made so a generator can be rebuilt even if damaged this way."
John Regan did not mention it but, yes there is something different about a Model T (generator) charging system. The Model T generator is third brush regulation type generator. Inherent in the design is its capability to destroy itself under the conditions John R. describes in Paragraph two above.
NEVER operate a Model T generator without the battery disconnected. If you must place a small wire on the generator output terminal and connect the other end to ground under one of the cutout mounting screws. In doing this the generator cannot enter the loop John R. describes thereby destroy itself.
Ron the Coilman
Typo I think, "NEVER operate a Model T generator without the battery disconnected." Shouldn't that read "NEVER operate a Model T generator with the battery disconnected."?
Thanks for the explanation. I learned something today. It's good to know, as I would have not thought twice about running the car with the battery disconnected.
I remember a thread about model T's being shipped to dealer with no battery having just such a jumper wire to ground the generator. It had a little tag to remind the dealer to remove it when the battery was installed. There was a picture of one. There was some debate about it being among the most rare model T parts, despite being made by the millions, as they were thrown away at the dealership. Does anyone have one?
Read paragraphs 1107 and 1109 in the Ford Service manual.
Also, read the owners manual (below is from the 1921 edition):
Can the Engine be run with the Generator disconnected from the battery? Answer No. 136
If for any reason the engine is run with the generator disconnected from the battery, as on a block test, or when battery has been removed for repair or recharging, be sure that the generator is grounded by running a wire from the terminal on generator to one of the dust cover screws in the yoke. Two strands of shipping tag wire may be used for this purpose. Be sure that the connections at both ends of the wire are tight. Failure to do this when running the engine with the generator disconnected from the battery will result in serious injury to the generator. Never ground the generator through the cut-out.