Hi everyone. I'm a newbie here and have some questions concerning my 26/27 model T restoration project. I am wondering if I have something not wired correctly. I have followed the wiring diagram that came with my wiring harness but I have spark at the wire that goes to the generator with the switch on or off. That can't be right! Is something missing? BTW. The generator is not charging and I now have it apart. Any help is appreciated.
The battery is negative ground. If you have that backwards then you get a big spark as you describe.
I don't know what diagram you have, but maybe this one will help.
I see that this is your first post to the forum. Welcome to the affliction!
Royce is correct and Steve's wiring diagram is spot on about the Model T being a negative ground vehicle.
The wire to the generator's cutout (that small "can" on the gen) is ALWAYS live. There is battery voltage at the terminal even when the key is off.
A spark when removing or connecting the wire suggest that your cutout is bad and is allowing battery current to flow into the generator, this should not happen. Voltage should be flowing out of the generator (charging) when the engine is running.
You may have multiple problems, among them: a bad cutout and a generator with one or more issues which prevent it from charging. Good luck with your project. Bill
The problem could be the cutout cover is touching the terminal where you connect the wire. If you have a ohm meter, only $5 at Harbor Freight, measure to see if the terminal on the cutout is grounded. The battery should have a negative terminal grounded to the chassis. A positive ground will work if some expert changed it in the past, however if that were the case, it would still be working correctly.
Another test is to use the DC current range on the meter to actually measure the current, that would answer most questions.
Thank you all for your informative responses! This forum is full of great information from good people and I have been reading and learning from you for some time now. I will have to get the service book. I will check my wiring as per the diagram from Steve and I do have negative ground.
It would seem that I have the wiring correct as per Bill and Tony because that wire is "always live". I will check that all out today after I get the generator back together. Thanks again for your inputs. LJB
Do you get that spark when you touch the wire to something grounded such as the generator body, or when you touch it to the terminal on the cutout? The wire should always be hot in the direction of the battery, but the terminal on the cutout is only hot when the generator is charging. That is, when the engine is not running the current does not go toward the generator, but when it is running the current goes toward the battery. There are 3 types of cutout. The original equipment has a relay which operates when the generator is running causing a connection to the battery. With the relay type cutout, although the battery should be negative ground the relay will still stop current flow even with the battery reversed when the generator is not working. There is also the diode cutout a more recent type replacement. The diode is reliable and will allow the current to flow from the generator to the battery when your battery is negative ground, but if you reverse the battery, the diode will allow the current to flow toward the generator with the generator not running. The third type is a voltage regulator. The voltage regulator will have to be addressed by someone else, but I think (not sure) it would be ruined if the battery were reversed.
Martyn Vowell and I had some shorting problems when we Rewired Derrick Pang's Runabout. Turned out that the screw at the cutout that holds the wire was too long and was grounding out on the case of the generator. Then we knew why the original owner had washers packed under the screw head to act as spacers.
LOL, George, your story reminds me of something on my 1971 Plymouth GTX. When I took it apart, I noticed that one of the tail light sockets had an extra little jumper wire jammed in the side of the socket and going to ground.
Of course, such a thing wasn't OEM, so I omitted it during the restoration. Sure enough, when the car was finished, that light wouldn't work until I fabricated another short jumper wire to ground and jammed it in the side of that socket!
I use the model T service manual and several other books I have picked up in the last 6 months but generally can get information need from the forum members. Most of the forum members explain things they have done from experience in a simple manor Welcome to the forum.Tim
Hi guys. Thanks for the posts and the welcomes. I did not get much done on the generator today. We have a democracy in our house where I get one vote and my wife gets two. Haha!
Thanks Norm for explaining that in your post. That wire does spark when I ground it to something and should by the way it is wired through the ammeter to the live post on the switch and back through the fuse and to the positive on the battery. The horn is also live without the key on bat. I don't think that it sparks at the cutout terminal, which I would have noticed when I disconnected the wire, but didn't have it back together today. I will try again tomorrow. The cutout or voltage regulator that I have is one that is a couple inches high and rectangular shaped. About a 1.25 by 2.5 inches or so. If that tells you anything. I will try get it back together tomorrow and see if that sparks when I hook up the wire.
BTW. I checked out the generator best I could with a multi meter set for resistance and it looked good. Field not open or shorted and the armature also checked out. It all looked good inside and had a sealed bearing on the same side as the brushes so someone must have worked on it in the past. I don't think my dad opened the generator when he overhauled the motor about 25 years ago because when I took it apart there were two screws on the bottom plate gear side that were rusted badly and one broke. Luckily it broke at the head end and left me enough to grab on with a small vise grip. I had sprayed it yesterday with pen oil and it came out easily. They are #10 32nf thread so I found one and a few small lock washers in my little stash of tiny nuts and bolts. Incidentally the car has been in my heated to above freezing garage waiting for me to work on it since then so I don't think that it rusted while I owned it. Sorry, I'm blabbing.
I got the generator back in and checked the cutout and it seems to be fine. I will start her up tomorrow and see if I have better luck with it charging. I'll post tomorrow night.
Just wondering what the extra wire is for? It looks dirty right now but maybe a pinkish color. It comes out of the wire harness in the area of the timer generator.
On the '26'27, for the generator cutout, that wire is in the Lighting Wire Loom, p/n 5041E, (8 wires at each end) for terminal block, lights, magneto, starter switch and cutout. Runs with the longer small loom under the radiator to the passenger headlamp, contains the 2 (bright & dim) headlamp wires, and the generator/cutout wire.
Thanks Dan for that diagram especially. Shows nicely where the wires should go under the radiator to the passenger side. I have mine wrong. I have to check tomorrow where that spare wire comes from. This wire harness that I have came from one of the vendors about 20 years ago. I think the other end of it comes out near the coil box. I will check to be sure.
Glad to help, but noticed the Ford schematic has bad arrow pointing to the wrong harness!
On the description between the headlamps, for the "8-Way Cable." the arrow passes over the cable and ends at the Timer loom! That is wrong, the arrow point should have ended at the loom under the radiator! Perhaps the draftsman did this diagram on a Monday morning
Thanks again Dan. I finally got the generator installed and the cutout wired up. I took the cover off so I could see what was going on. The live wire from bat doesn't spark when I touch bat on the cutout. I started up the T and no charge showing on the ammeter so I went and pushed the cutout down to make contact. I could see that it sparked at the points so I taped them to stay touching and checked the gauge and it showed charging. So the generator is working but the cutout not making contact by current. I guess I will have to get a new one unless there is a fix for it. I guess the wiring was correct in the first place probably just the cutout was faulty.
I did check that pinkish wire that turned out to be a black wire with a small hole connector. That wire is not part of that 8 wire cable but is part of the timer/coil box cable. It comes out of that loom near the coil box and runs in the loom down about 12-16" along the motor where it comes out and is a single wire about 2' long. Both ends have the little hole connectors like would fit on a generator or cutout screw. It was taped to the coil/timer loom with enough left to attach to the generator or cutout but is or was not being used. I was just wondering what it might be for. In your diagram there is mention of a foot switch. Not sure what that is? Maybe that is what that wire is for?
Nice catch on the drawing Eagle Eye Dan!
Holding the cutout down and then seeing charging begin seems to most folks like proof positive that the cutout is bad. Not necessarily so. The generator must develop enough output on its own to pull the cutout in and thus operate it. When you push the cutout closed manually you are supplying more field current from the battery into the generator and it then can charge but it will soon stop when you lower the RPM and that can be caused by issues in the generator so don't be totally shocked if a new cutout has the same issue. Check for a DC voltage on the generator post when the cutout is NOT forced closed and rev up the engine a little while watching that voltage with an ANALOG meter to measure the rise of DC voltage. If the generator voltage gets up to 7 volts and the cutout has not operated THEN the cutout is bad. If the generator never rises up to 7V with increased RPM and before you manually close the cutout then the GENERATOR is defective and the cutout condition is still unknown and can't be tested easily until the generator is working right. Incidentally if you are NOT familiar with electrical stuff then I would strongly suggest you do NOT try to measure current by using the current scales on your meter since it is very easy to ruin a test meter by hooking up the test meter incorrectly for measuring current. Just stick to measuring voltage at various points and you won't hurt your meter and you will still be able to diagnose the T electrical issues. Digital type meters generally don't give accurate readings when the Model T engine is running due to ignition noise getting into the meter. Doesn't matter whether it is a cheap meter or expensive lab model - digital meters are not a good way to diagnose things like charging which has to be measured when the engine is running.
Wow! Thanks John for all that information. I do have an old cheap analog meter that should work for that test and will surely try that tomorrow.
You were right John! I tried to get some readings from the generator and nada. If I adjust the third brush is there a chance that I can get it to produce current?
I took the generator out again and got it spinning with a 6 volt battery. I then loosened the 4 screws holding the brush plate and moved it back and forth until the armature stopped. I locked it down and made sure the 3rd brush was movable by loosening the nut on its adjusting bracket. I have re-installed the generator and spent the rest of the afternoon lengthening the spark adjusting rod from the steering column. It took me a while to get that right and to get the 2.5" as recommended by the service book and forum members. I should now have the proper retarded timer which should eliminate the slight kick back that I was experiencing when starting with the starter motor. I didn't have time to start the car and see what I had accomplished but will do that tomorrow. Wish me luck!
What kind of timer are you running? The 2.5 inch measurement is only for stock Ford roller timers.
Here is another way to set timing that works for any timer:
Thank you Mark for that reference. I believe I have the Ford stock roller but not sure right now because I have not had it off. To be safe I will use the method in the discussion board and check the setting. I know that I will improve the kickback situation because I moved the timer at least 3/4 " in direction of retard.
Just to finish this thread. I thank all for your responses and as a result have found that I do have the car wired correctly! I learned a lot about the generator and timers. BTW. I did start the car today after having to take the bendix cover off and finding that the starter gear was slightly jammed against the stop. Just turned it with my fingers to get it going and put it back together and the T started right up. I'll be starting another thread if that condition persists. I will start a thread concerning popping in the manifold and I will be taking the generator to someone who can check it out. Still no charge from it.