Coil wire hot?

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Model T Ford Forum: Forum 2016: Coil wire hot?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry Pierce on Sunday, January 03, 2016 - 04:43 pm:

On my '26 Tudor, I'm not getting any fire (to start). Using a test light, the coil wire isn't hot, either in mag position or battery. Is this normal on these? On my other cars, when the switch is on in run position, the coil wire is hot. Can someone enlighten me and does anyone have a wiring diagram I can use? Thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Sunday, January 03, 2016 - 05:01 pm:

Depends on which coil wire you are testing. The wire at the bottom of the coil box on a 26 should be hot all the time the switch is turned to battery. It will be zero when the switch is on magneto if the engine is not running. If the engine is running your needle will read anywhere from 6 volts AC to 30 volts AC depending on the speed of the engine. The magneto only works when the engine is turning and creates higher voltage as the engine speed increases.

The wires at the lower side of the coil box will be grounded as the engine turns. Each wire will be grounded in the firing order 1,2,4,3,1,2,4,3 etc. You won't be able to read this on your volt meter, however if you are switched to battery, as you turn over the engine you will hear each coil buzz as the timer grounds the lead to that coil. You can also test without turning the engine by grounding one wire at a time and the corresponding coil should buzz.

The upper wire which leads to the spark plugs will give you a very high voltage, but I don't recommend you touch it or try to check it with a volt meter. You can see a spark jump if you pull the spark plugs out and lay them on top of the engine and crank the engine over. Each plug should spark in firing order.

To check for proper timing,leave the plugs laying on top of the engine and push the timing lever all the way up. Turn the engine until you feel compression on cylinder #1. After the piston starts down about 15 degrees, you should have a spark on spark plug #1 with the ignition on battery. If the spark comes another time, your timing rod needs to be adjusted. If it comes on another spark plug, your wires are mixed up and should be connected to the coil corresponding to the cylinders to spark in the timing order 1,2,4,3. You will get two sparks per revolution of the crankshaft. The first spark on #1, the second spark on #2. Then for the next revolution of the crankshaft #4 and #3.

Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry Pierce on Sunday, January 03, 2016 - 05:08 pm:

No, the wire at the bottom of the coil box and at the switch are not hot, either on mag or bat position using a test light. I have the switch hanging out of the dash to access the rear wire mounting screws. The car was running when I took it apart for paint, etc. Now no fire to bottom of coil box in either position..


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Sunday, January 03, 2016 - 05:57 pm:

What Jerry posted.

Here is a wiring diagram for the '26. The blue/yellow tracer wire goes to the bottom of the engine mounted coil box.

You mentioned the T was apart for painting, be sure you have filed or ground away paint/primer from all important contact points to have a good ground from the T's 6v battery to frame/engine/metal paths to any electrical part.


Top of pagePrevious messageNext messageBottom of page Link to this message  By keith g barrier Savannah Tn. on Sunday, January 03, 2016 - 07:28 pm:

Just make sure that you don't apply battery voltage to the mag terminal ! KGB


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker, Ramona, CA on Sunday, January 03, 2016 - 07:59 pm:

The power (normally 6 volts when switched to battery enters the coil box thru the bottom connection. To me it sounds like the wire is shorted to the coil box. Look at it carefully, use a mirror if necessary to make sure when it was reconnected it did not touch the body of the coil box.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, January 04, 2016 - 09:18 am:

I think Norman mispoke when he said that the lower side terminals are grounded by the timer. He meant the UPPER side terminals are grounded in turn by the timer. The LOWER side terminals are the spark plug connections. 26/27 are known to have troubles at the ignition switch itself so check the BAT connection at the ignition switch to make sure it has power and then check the coil connection at the same switch back location when the key is in the BAT position which should then cause a connection from the BAT connection to the COIL connection if the keyswitch is working properly.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, January 04, 2016 - 01:12 pm:

John, you are correct. I made a mistake.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry Pierce on Tuesday, January 05, 2016 - 03:15 pm:

I have nothing at the coil connection on the back side of ignition switch when switch is in BAT position, no fire. Could the contact inside have gone south somehow? The only thing that lights my testlight is the BAT connection, nothing else. What's weird tho is the damm thing was running before I pulled it apart. Go figure


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Tuesday, January 05, 2016 - 04:30 pm:

The switch itself is not working. You can get new parts for the switch. There are two types of switches for the 26. One has 4 tabs holding it together. Be very careful bending the tabs so that you don't break them. The plate with all the contacts can be cleaned up or replaced. The other kind of switch has 4 pins which fit into slots and are rotated into position. So if you order new parts, get the correct part for your switch.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Tuesday, January 05, 2016 - 05:21 pm:

Norman is right. If you need to order new parts, first take your switch apart and look what you need and order what you need. My experience with the rebuild of the switches is that the new parts can be bad to. I learned it the hard way and blow out my magneto due to a short in the switch with the new parts.
In the 1926 touring I have always a simple three way switch with wiring.
The middle post is connected to the coil terminal the left to the battery and the right to the magneto terminal on the model T switch. It is easy and fixed in a few minutes if your original switch dies during a run.

Andre
belgium


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry Pierce on Tuesday, January 05, 2016 - 07:19 pm:

Thanks everyone for the help. I'll take the switch apart and I'll bet something broke or wore out. Can order rebuild kit from Langs. Thanks again.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Tuesday, January 05, 2016 - 07:50 pm:

Suggest you have Ben Martin rebuild your switch.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel D. Chicoine, MD, Pierre, SD on Tuesday, January 05, 2016 - 08:11 pm:

My 26 switch was fried inside and shorted out the magneto. Mr. Ben Martin did a wonderful job of repairing it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Brough on Tuesday, January 05, 2016 - 09:13 pm:

Isn't there a way to just bypass the switch temporarily and get power to the coil and start the engine?

Wouldn't that prove that the switch was the problem?

Is there an amp gage in this car and is the power to the amp gage and out of the amp gage to the switch connected properly?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Wednesday, January 06, 2016 - 11:49 am:

Take the wire off the coil box and run a jumper from the battery wire to it. Might want to add a switch or use alligator clips.


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