Stupid coil question

[vwjoe]

I got a 12v coil and replace about ten already in a year they keep burning up on me. Any ideas on this. Also is there any were i can find a wiring diagram for a vw trike...

[KDHUFF]

I think you may have it wired up hot all the tiime, thats the only reason I can think of that would burn them up. make sure its not getting power with the key off. just a guess I am sure someone that knows about that stuff will reply soon. I just know I have never had one go bad.

[vwjoe]

No its not hot all the time I checked that. I did just install a 20 amp fuse inline link. I hope this will take care of problem.

[Ol' Grey]

A bad ground or worn/faulty spark plug wires can also cause coils to go south quicker than normal.........

[Rsw]

Does a coil take a full 12 volts? I remember wiring my old chevy truck with a hot wire and and a old mechanic had me put porcelain resister like out of a old Dodge before the coil to back the voltage down.

[Ol' Grey]

Does a coil take a full 12 volts? I remember wiring my old chevy truck with a hot wire and and a old mechanic had me put porcelain resister like out of a old Dodge before the coil to back the voltage down.

Here's a random link that might explain what your mechanic bud was showing you:

Heavy-Duty External Ballast Resistor for Ignition Coils, Points and Electronic Ignition Systems

On older conventional coils, yes, the coil will take the full 12 volts, it'll actually take the normal charging voltage of around 14.5 volts and boost it up to around 20,000 volts (up to around 60,000 volts on the newer electronic ignition vehicles) for firing the spark plugs.

The coil has primary and secondary windings (circuits). The windings can be 200 turns (coils) of heavy gauge wire in the primary winding and more than 20,000 turns of lighter gauge wire in the secondary winding. When the conventional points are closed, the primary winding takes in current from the battery and starts to increase the voltage, exciting a magnetic field. When the points open, it grounds the primary circuit, which collapses the magnetic field and the current then flows into the secondary circuit where it steps it up to the higher 20,000 volts and fires the spark plugs.

Both primary and secondary circuits require a certain amount of resistance, which is measured in ohms, maybe 1.5-3.5 ohms on the primary side and maybe 7,000-25,000 ohms on the secondary side.

I'm guessing that your mechanic friend was adding resistance to the primary circuit to prevent pitting/burning of the points..........

[Ol' Grey]

vwjoe........I looked at the above link again and it mentions air-cooled VW's as being a vehicle it's recommended for to help keep the coil cooler. My electrical knowledge is basic, but this or another similar product might be worth looking into ?

[Ol' Grey]

Does a coil take a full 12 volts? I remember wiring my old chevy truck with a hot wire and and a old mechanic had me put porcelain resister like out of a old Dodge before the coil to back the voltage down.

Time to hit the hay here, but wanted to thank you for mentioning this, "Rsw"....I learned something new tonight and because of your input, this might be an option for "vwjoe"..........Credit belongs to you, Amigo!

Ride Safe...........

[Rsw]

Time to hit the hay here, but wanted to thank you for mentioning this, "Rsw"....I learned something new tonight and because of your input, this might be an option for "vwjoe"..........Credit belongs to you, Amigo!

Ride Safe...........

Thanks Ol' Grey.. that has been over 25 years ago that I did that. But if I remember right he said the resister lets the car to start under full voltage for cold starts and then backs the voltage down as the motor warmed up. vwjoe, if this does turn out to be the problem, carry a extra resister with you. If your trike ever starts to just die on you driving down the road or wont start, switch to the new resister. They do go bad without any warning and any reson.

[Woolie]

My manual says the 12 volt OEM coil has the resistor built into the coil. The resistor in this circuit is not going to do a lot to reduce the voltage but is there to reduce the current used by the circuit. The current is what produces the heat and destroys the components. Here is what it says:

1. The ignition coil steps up battery voltage high enough to jump the gap on the spark plugs. The coil is mounted on the fan housing adjacent to and above the distributor.
2. Inspect the coil wires and insulating tower for damage, splits, cracks, and carbon tracks.
3. Check the routing of the wires to the coil. If the wires to terminals 1 and 15 are reversed, the engine may run, but will misfire under certain conditions.
4. Using a voltmeter, turn the ignition on, engine off (do not operate the starter) check for positive voltage at terminal 15. On 6 volt models, at least 4.8 volts should be reaching terminal 15; on 12 volt models, a minimum of 9.6 volts must be available. If not, trace and repair the wiring.
5. If sufficient voltage is reaching terminal 15 on the coil, disconnect the high voltage wire (terminal 4) at the distributor cap end and check for a spark as described in section six.
6. If there is a strong spark, check the ignition points and condenser and replace as necessary.
7. If the points and condenser are OK and sufficient voltage is present at terminal 15, replace the ignition coil. Caution: Use the correct coil for the application. Coils used on 12 volt models have an internal resistor to reduce power going to the windings. Models with 6 volt systems do not have a built in resistor. Use of a 6 volt coil on a 12 volt system will result in burned points; a 12 volt coil on a 6 volt model will not produce enough voltage.

I know you did not need all that information but I included it directly in the test section from the manual. According to this I suspect the coil does not have the resistor and the current passing through it could eventually cause failure. Are the points burned, that would be an indication of the missing resistor.

[vwjoe]

Yes I think for 14.00 bucks I am going to add a resistor. The coil does get hot so hot you can not even hold it. I did check double check and triple check everything everyone said so I will ad a resistor even if not needed it will be a good measure i think. Thank you all for your ideas and input. This site so rocks...

[Padre1357]

heres a basic wiring diagram site
Free VW Trike wiring diagram

[vwjoe]

Thanks padre I been using rat race wiring guides already.

[aussiei]

TheSamba.com :: View topic - Trike wiring idea's?