Magnetronic intermittency is unusual. Regrettably all manufactured products can fail, but intermittent working of a Magnetronic ignition is most often the result of vehicle earthing issues.

 Magnetronic electronics are sensitive to vehicle earth issues because the electronics connection to the negative terminal of the battery is through the distributor base plate, the earth strap between the base plate and the distributor body, the distributor clamp, engine block, engine earth strap to vehicle earth and finally the battery earth strap to the battery. Consequently the sum of small resistances along this extended path can in extreme cases degrade Magnetronic module voltage to a point where it switches off.

When an engine heats up earth connection bolts can expand and loosen which can increase the resistance of an earth connection - especially in dry weather when moisture is not present to reduce connection resistance or on starting when there is a drop in battery voltage.

Check the Magnetronic adaptor plate is making clean, oil free contact between the base and adaptor plates and everything is firmly screwed down. Also check the earth wire between the base palate and distributor body is making a sound connection.

Then temporarily connect a wire directly from the negative terminal of the battery to the distributor clamp and see if the situation improves.

 If it does, check all earth connections between the engine and battery terminal are clean, tight and low resistance.  This might not only cure the identified problem, but improve starting, battery charging, spark energy, headlight brightness, etc.

 If this does not improve the situation Autocar can check module operation for you or supply a replacement power module if required.  

 Checking  module operation is free under warranty but a charge will usually be made for Magnetronic ignitions over 3 years old and outside the normal warranty period.