I'm checking all my wiring, preparing for the big day of first startup. I'm a little confused about the wires from the coils to the timer. With the wires connected to the coils, but not to the timer, I show continuity between all four wires. With the wires disconnected from the coils , I can isolate each wire to know where they connect to the timer. I've looked at wiring diagrams, but can't get my head wrapped around this.
When checking continuity of timer to coilbox wiring you must remove all four coils from the coilbox.
Here is a easy to use AND CORRECT March 1922 to 1927 Model T Ford wiring diagram.
Nope. No good. At least as I understand your posting. You're saying you're getting an ohm reading between all the timer/coil wires with the harness disconnected from the timer but it's OK when disconnected from the coil box. That eliminates the harness. Probably inside the coil box is where the problem lies. Pull the coils and re-check though I don't believe it'll matter since there's no way these 4 wires can be connected thru the coils anyway. Moisture, carbon track, something along those lines.
I have already cleaned everything inside the coil box. Everything inside shines like new. Thanks.
Doesn't matter how clean it is if the problem, (as I believe you're describing it), still exists. There should not be continuity between those 4 wires under any conditions. If all 4 wires were actually connected (continuity between them)all 4 coils would fire whenever the timer rolled over a contact.
If the coils are in place there will be a common connection thru the bottom buss strip. Removing the coils will isolate each wire.
Did you paint the wood for the coil box? If you did and used a black carbon based paint, the carbon could act as a conductor and could short the box/wiring out.
The common power connection has no bearing on the problem. He's stating the timer wires are connected together (continuity between the wires). Should not be happening. I'm still with the box as his problem if it's what he actually means in his posting.
No paint on the inside.
Tom: did you take the box apart and if you did are the timing harness connections properly insulated from the box? Is you car equipped with a battery? If the problem exists as you describe it, and it's the box as I suspect, all the coils will fire when you turn on the ign. switch to battery because their grounded to the box.
Another check concerning continuity: with the timer wires disconnected from the box check for continuity between the terminals and check for continuity between the connections and ground (any metal: frame engine) If there's a reading between the terminals and ground the terminals are grounded and should not be.
If I understand what Tommy is saying, there will be "continuity" between all four wires to the timer. The path is from any terminal to the coil, thru the coil to the bottom rail and then back thru another coil to the terminal. It will not be a short as each coil primary is about 12 ohm so a careful measurement will be about 24 ohms.
This can be checked by removing the coils. If after removing the coils there is still continuity, the coil box is bad...
I think Tony has the answer. Tommy is reading current through multiple primary circuits in series which are all tied together by the bottom contacts in the coil box.
Checking this evening, with coils out of the box, I get no continuity from terminal to terminal as before.
Now checking my switch, it appears that I will be ordering a rebuild kit. I have both a pin style and a "bent prong". I am going to try to use the pin style.
Have you looked inside the switch to see what's wrong with it? Sometimes the back plate is warped and all it needs is to flattened by rubbing it on sandpaper.
Thanks Steve, I did have a look inside and plan to sand it and lift the contacts a bit before I order any parts.
I sanded the plate and cleaned the contacts. I think it will be good now. I have looked at several switches and pictures of switches but mine is a little different. One terminal that is marked DIM on others is marked SIDE on mine. The one marked BRIGHT on most is marked HEAD on mine. The manufacturer name on mine is CASKEY-DUPREE , MARIETTA OHIO.
I suppose the findings with my ohm meter are as they should be. I see continuity between BAT and SIDE/DIM and TAIL then between BAT and HEAD/BRIGHT and TAIL so the light portion of the switch should be good. For the ignition part - key off I get cont between COIL and GROUND . Good ? Key on BAT I get cont between BAT and COIL. Key on MAG I get cont between COIL and MAG. Sound normal? I'm pretty sure that the GROUND wire went to the junction block on the firewall. Where does the ground wire attach to an actual ground connection? The diagram doesn't show a ground connection on the switch. Thanks.
The ground connection on the switch is not used on a Model T. You do not have to ground the switch.
Tommy, use a GOOD meter and do not rely on the continuity buzzer as it will sound at more than twelve ohms thus fooling you. There is no ground wire to the coil box. The timer grounds each coil in sequence. 1 2 4 3.
Not only do you not need a ground you should not install one. Having a ground wire at the switch just increases the odds that something will be accidentally grounded and that can cause serious issues for the wiring and electrical system. Omit the ground at the switch totally.
If your switch back has a ground on it, and some do, just don't use it.
So when the key is in the off position the center, coil terminal should not have continuity with any other terminal? Not grounded , just nothing? Thanks