Fairly basic electrical questions (620)

[Mysta2]

I've got a lot of rotten wiring in my '79 620 and currently I have no spark.

 

So I've got some wiring to dig through and probably replace, but I've got the following questions:

 

What does the ignition module do? The coil boosts the voltage from the battery, the distributer times the spark, what more is needed?

 

I don't understand the purpose of a fusible link. Can I replace this with a fuse? If so, what rating is the link supposed to fail at?

[Lockleaf]

Fuses come in 2 "styles", fast burn and slow burn. Slow burn fuses will allow for some short term over voltage before burning up. Fast burn are instant, they blow the moment they hit peak amperage.

 

Fusible links are slow burn. You would need to replace it with JCAS or MAXI fuses in order to preserve that burn rate.

 

The links are color coded.

 

 

Ignition coils function by inducing a magnetic field and then collapsing it rapidly around another coil. That is how they boost voltage. The ignition control module is how the car controls that process. On older cars this same job was done with points.

[Draker]

The Ignition Module cuts power to the coil to allows the magnetic field to collapse and fire a spark on the secondary side.  

[Draker]

12v on the primary, when it collapses it's like 20k-40k volts on the secondary. Low current, but it still hurts like a mofo.

[banzai510(hainz)]

what year or type of distributor you have?

 

turn key ON do you have 12volts to the coil?  Yes or NO?

[tr8er]

The ignition module is just a smart relay. Controls the gate between coil and plug.