Where is the negative side for my ignition coil?

For the 1972 VW Beetle, the ignition coil is typically connected to the positive terminal of the ignition switch, and the negative side of the coil is connected to the distributor. The distributor then sends the spark to each spark plug to ignite the fuel in the cylinders. The wires going to the ignition coil should be two different colors: one for the positive side and one for the negative side. The positive wire should be connected to the ignition switch, and the negative wire should be connected to the distributor. Regarding the voltage regulator, if you are not getting any current on one side of the prongs, it could be a sign of a faulty voltage regulator. However, it's also possible that there could be a wiring issue or a bad connection. One way to test the voltage regulator is to use a multimeter to check the voltage output from the regulator. You can also check the wiring and connections to make sure everything is secure and not damaged. It's worth noting that the generator and voltage regulator system in the VW Beetle is a bit different from modern alternator systems. If you are not familiar with working on vintage VWs, it may be helpful to consult with a mechanic or VW specialist who has experience with these types of systems.

How stock is ignition and charging system?

Assuming stock ignition, check for near battery voltage (within 3 volts or better) at the positive side of the ignition coil while the ignition switch is in the run position.

If no power at coil positive then likely a fuse has blown or other open circuit... miswire or open ignition coil resistor wire.

If power at coil positive, check for power at coil negative. If near battery voltage at coil negative then points are open and you should get spark at ignition coil secondary by flashing the coil negative with a jumper wire to ground.

Comment for further assistance.

The wire from the distributor to the coil goes on the negative side of the coil, the positive side of the coil gets power from the ignition switch

Disconnect the ignition coil output wire at the distributor cap.
Connect a spark plug to the end of the ignition coil output wire which you just disconnected.
Connect a ground wire to the threaded portion of the spark plug.
Disconnect the ignition coil ground wire from the negative terminal on the coil (Green Wire).
Connect one end of a ground wire to the ignition coil negative terminal.
Turn the ignition switch to the ON position.
Tap the other end of the ignition coil ground wire jumper on an good grounding point (for example the battery negative terminal) and look for sparks at the spark plug that correspond to the frequency of your tapping of the ground wire.
If you have a good spark at the spark plug, the ignition coil is good.
If you don't get a good spark, check for approximately 12 VDC from the coil positive terminal (black wire) to ground with the ignition switch in the ON position. You should also get approximately 12 VDC from the coil negative terminal (Green wire) to ground
Ignition Coil Resistance Check

In addition to the test above, you may elect to perform an ignition coil resistance check as confirmation of the coil's condition.

Check the ignition coil primary coil resistance by connecting an ohmmeter between the positive (Black wire) and negative (Green wire) terminals on the coil. The resistance should be 0.4 to 0.6 ohms.
Check the ignition coil secondary coil resistance by connecting an ohmmeter between the coil output terminal and the ignition coil negative terminal. The resistance should be 5000 to 7200 ohms.

You may have a bad coil or bad ground or wire connection

There is usually a wire from the coil that goes to the negative side of the coil while the positive side goes to the ignition switch. Without knowing more about your car and engine, that is the best info I can provide.

The Black wire will connect to body ground, and it should be a good solid ground and if this wire is not grounded well then you might receive a primary voltage shock if you touch anything that is metal or grounded inside of the vehicle when the engine is running.

The Red wire should be connected to power when the key is in the "Run" position only, and a good place to find that source is one of the "IGN" connections at the fuse panel using a covered female spade connector. Use a test light and be certain that the connection only has power when the key is in the "Run" position, and has no power when the key is in the "Off" or "Accy" position.

The White or Yellow wire should connect to the "LPS" connection at the fuse panel next to the LPS fuse using a covered female spade connector.

The Green wire will connect to the "-" negative side of the ignition coil or the primary side of the ignition coil, and for later model GM HEI equipped vehicles this will be the "Tach" connection next to the main "Bat" connection on the distributor cap if the ignition coil is mounted inside of the distributor cap, or to the "Tach" or "Test" lead that runs from the negative side of the ignition coil if the ignition coil is mounted separate from the distributor. To locate the lead run down the wire from the negative side of the ignition coil and the lead should break off from that wire and it should have a tag on the wire that will say either "Tach" or "Test" (sometimes it is just an empty black wire connector) and that is if the lead does not come straight off from the wire connector at the ignition coil. If there is no lead you can get a wire tap connector to tap into the wire from the negative side of the ignition coil and then use a covered male spade connector to connect the Green wire from the tachometer to the wire tap connector.

Here is a diagram to help assist you although it might be hard to make it out, and let me know if you require any further assistance.

Ignition Module REMOVAL & INSTALLATION

1. Turn the ignition key to the OFF position.
2. Separate the wiring harness connections.
3. Unbolt the igniter.
4. Loosen the nut holding the wire lead onto the coil.
5. Tag and disconnect the wire lead.
6. Lift the igniter off its mount.
7. Installation is the reverse of removal.

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The following is related by not the same as the 'ignition module.':
Ignition Coil TESTING 1994–95 Models

1. Turn the ignition key to the OFF position. Disconnect the negative battery cable. Wait at least 90 seconds from the time the negative battery was disconnected to start work. CAUTION
   Work must be started after 90 seconds from the time that the ignition switch is turned to the LOCK position and the negative battery cable is disconnected from the battery.
   
2. Using a 5mm hexagon wrench, remove the 2 cap nuts and the V-bank cover. Fig. 1: Remove the V-bank cover, a 5mm hexagon wrench will be needed — 1MZ-FE engine
   
   
3. Disconnect the ignition coil wiring from the coil being tested. Fig. 2: Disconnect the ignition coil wiring from the component being tested — 1MZ-FE engine
   
   
4. Insect the primary coil resistance using an ohmmeter. Measure the resistance (cold) between the positive and negative terminals. Resistance should be between 0.54–0.84 ohms. Fig. 3: Attach an ohmmeter to the positive and negative terminals of the coil — 1MZ-FE engine
   
   
5. If the resistance is not within specifications, replace the ignition coil.
6. Reattach the ignition coil wiring.
7. Reinstall the V-bank cover. Push on the cover until a click is felt, then tighten the cap nuts.
8. Connect the negative battery cable. Reset any digital equipment such as radio memory and the clock if necessary.

Ford Crown Victoria, Mercury Grand Marquis, Marauder, Lincoln Town Car 1999-2005

Ignition Coil - Removal & Installation

1. Disconnect the negative battery cable.
2. Disengage the TFI-IV harness or the engine control sensor wiring connector from the ignition coil, as applicable.
3. On the 3.8L engine, disengage the engine control wiring connector from the radio ignition interference capacitor.
4. Remove the ignition coil retaining screws and the ignition coil and radio interference capacitor (if equipped) from the ignition coil mounting bracket.
   

Fig. Ignition coil and related components-late model 3.8L shown



Fig. Remove the ignition coil retaining screws



Fig. If your coil has this kind of build-up, it needs a good cleaning



Fig. This is the coil wire. Replace it if it looks like this

1. Remove the ignition coil cover from the ignition coil by releasing the locking tabs on both sides of the cover, then remove the ignition coil.
   

To install:

1. Install the ignition coil, then attach ignition coil cover, making sure the cover is firmly in place.
2. If removed, connect the ignition coil and radio interference capacitor, then install the ignition coil retaining screws. Tighten the retaining screws to 25-35 inch lbs. (3-4 Nm).
3. Connect the coil wire, then engage any electrical connectors that were removed.
4. Connect the negative battery cable.

Hope help with this (remember rated this post). TY for using Fixya.

If you have a good look at the coil, it should still have a positive and negative sign on it somewhere. Try not let the extra wires confuse you too much. These are for the ignition module in the distributor. let me know if you need further clarification after you've had a look.

the yellow blue is the + side of coil but to be safe get a test light connect one end to the negative side of battery or a good clean earth on the engine turn ignition. Check which wire has power .The one with power is for the + side of coil . Check test light on battery to make sure it works