123Ignition in a Volvo with Armored Cable  
Feb 2016 Ronald Kwas  [Comments added.]

Note:  The following information has been put together with the utmost care, and I absolutely stand by it, but must be used in conjunction with normal, cautious shop practice!  Work Safely!

This Tech Article is also available in German for my Volvoniac friends:  123Ignition im Volvo mit Panzerkabel 

[Notice:  The four fuse fuseblock of the 122 model is shown in the following Wiring Diagram, but the information presented here applies equally to the 1800 model!]


Background:  Installation of electronic Ignition modules such as the 123Ignition available from Skandix are a popular remedy for Ignition problems, such as inconsistent timing due to a worn Lobeshaft of the Distributor.  A momentary Start Switch such as the SW-EM Start Switch Upgrade, used to prevent key fatigue and breakage, is also a popular installation.  This information is intended to clarify the interaction of both, because...
1.  ...the Wiring Diagram published by Skandix contains an error...and...
2.  ...this diagram is missing important and relevant information. 

The following Information will explain and clarify the interaction and installation of both.  It actually applies to all electronic Ignition Modules, but the 123Ignition is shown as a particular example, because of points 1 and 2.   

Wiring Diagram published by Skandix.  Error is highlighted.

Explanation:  No direct connection exists between Ignition Coil power and terminal 50, as is shown in the Skandix diagram!  Ignition Coil power is supplied in Key position 3 and 4.  Terminal 50 is supplied with power momentarily, when Key is turned to Position 4 (Starting).  At the same time, power to terminal 54 is interrupted (Load-Shedding).

Ignition Switch Positions and Function: 

If Ignition Module were supplied by terminal 54 only, it would clearly not be supplied with power when turning Key to Position 4.  Because of this, either O'Ring diodes from terminals 50 AND 54 (or a single diode from term 50, see "Understanding the Failure..." Link below!) must be installed to power the module, as shown here:


OR...as shown in the Skandix wiring diagram, a Toggle Relay must be installed.

BUT...because many install a momentary Start Switch (such as the SW-EM kit) to prevent the well known Key fatigue, key Position 4 is no longer used for Starting. 

This means that a Toggle Relay or OR'ing diodes are only necessary if no Start Switch is installed. 

If a Start Switch is present, or installed at the same time as the electronic Ignition Module, the Toggle Relay or OR'ing diodes are unnecessary!


Correction and Changes:

The same Wiring Diagram with Correction and Changes.


Link:   Understanding the Failure of a Diode ORing Cable used with Electronic Ignition Module:   http://www.sw-em.com/Volvo%20Ignition%20from%20Scratch.htm#Failure_of_a_Diode_ORing_Cable


My e-mail answer to a question on reliability and general comments electronic Ign conversions:  

"...as far as being reliable...if that is your goal and target, NOTHING beats a points ignition, when properly set up initially, and then (only occasionally) maintained [See ancient SW-EM Tech Article:  A Tune-up out of Guilt or One Set of Points Outlasts the Clintons. ].  I have no electronic ign in any of my cars, (although being an electronics engineer with full knowledge of their advantages, [and disadvantages, with actually reduced spark energy due to the forward voltage drop of the transistor switch in the elec Ign, which replaces the points contact.  See Link to a great explanation by 142guy: PLACEHOLDER ]...but also being aware of cost-reduction of consumer products, and what that does to their reliability!).

...I also understand some some people like the maintenance-free nature of electronics...then again, increasing the complexity of a system inherently decreases the reliability, (we're not talking high rel mil avionics here!). [...where ultra-conservative, redundant design, first quality and even pre-screened, selected components as well as burn-in reliability testing are employed to make control systems very hi-rel!] and I have heard of the Pertronics failing out of the blue...and when they do, you are stranded...NO THANKS for me!...ask around on the forums for the experience of others, and you will get them from both ends of the spectrum...in the end, what you prefer is your call!" [...and in light of the experience of getting 50k+ miles out out one set of Points, see above!...I've made mine!] 




External material sources are attributed.  Otherwise, this article is Copyright © 2001-2021.  Ronald Kwas.   The terms Volvo and Skandix, and 123Ignition are used for reference only.  I have no affiliation with these companies other than to try to keep their products working for me, help other enthusiasts do the same, and also present my highly opinionated results of the use of their products here.  The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at, at the readers discretion.  As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles! 

You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source.  If you donít, youíre just a lazy, scum sucking plagiarist, and the Boston Globe wants you!  As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the odd metaphor and probably wise-a** comment. 


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