1800 Ignition Wiring...Swedish vs. British Design

Comparing Swedish and British designed Automotive Electrical Circuits.                                                                                    4 - 10 R. Kwas


Philosophical Differences in Design:  Comparing the Volvo 122 and 1800 wiring designs with an emphasis on Ignition reliability, a philosophical difference is immediately apparent to the writer.  Whereas the Amazon uses a simple, single, uninterrupted wire to supply Battery Power to the Ignition Switch, with the apparent Swedish Philosophy:  Simple is Best and Most Reliable, “Ja Sure(!)”, the 1800 uses a “Daisy Chain” principle…that is, the wiring supplying Battery Power to the Ignition Switch follows a circuitous path and has multiple connections, including series connections, en route to the Ignition switch, with the apparent British Philosophy:  As Long as it Gets There, it’s “Jolly Good(!)”  Daisy chaining is typically used where connections must be made to multiple points opposed to “starring out” multiple wires from a single source point (see FIGURE 1), and this is not a problem per say if implemented well, but it is not implemented very well in the writer’s opinion in the 1800.  Because the way it is implemented in the 1800, if any of the series connections in the daisy chain upstream of the Ignition switch develops problems, vehicle Ignition itself is at risk of failure!


FIGURE 1.  Comparing Daisy-Chain and Star Wiring.  Star strategy requires more wire, but does not bring with it the
risk of everything downstream of a problem connection being affected.  This is carefully considered during the engineering
of a wiring harness, and apparently should have been considered a bit more carefully in the 1800! 


More specifically, both Amazon and 1800 source power to the Ignition Switch Terminal 30, from Starter Motor Terminal 30 (bolt which also has the heavy gauge wire directly to battery) but that’s where the similarity ends and a noticeable difference, which impacts Ignition reliability, begins.  The 1800 Ignition power wiring runs by way of two screw-fastened terminals at the B+ connection of the Regulator, and then by way of two push-on terminals at the Fuse Block Fuse 1 (yes, the Lucas one!!).

FIGURE 2.  Girl finds out about 1800 Fuseblock by Lucas...or see the whole video:  LINK


Only after this circuitous routing and its connections to the Lucas electrical aberration, does it finally get to the Ignition switch.  It is a seemingly minor point, but considering the critical vehicle function (this also supplies the vehicle Ignition, which is kinda important!); these terminal connections along the way are just not at the high level of reliability where they should be!  See FIGURE 3.  The wires themselves are soldered to the terminals on the 1800, which is actually a harness construction feature to be commended(!), and it is in-fact better than the crimped only connectors of the Amazon because soldering gives the highest level of reliability to the actual wire-to-terminal connection, but in sharp contrast to this, they totally dropped the ball after that, because if any of the mechanical connections of those terminals along the way starts degrading over time due to looseness or corrosion, or a combination of both, as is known they certainly can, and add resistance or intermittence into the current path…flaky operation of all the downstream loads (including the Ignition in the 1800!) will surely result.  I suggest these (along with the remaining push-on connections of the Ignition Fuseblock) are significant contributors of electrical unreliability, including intermittent Ignition failure issues on the 1800 (LINK), aka "Inexplicable Lucas Incident".


FIGURE 3.  1800 wiring diagram excerpt showing (less than absolutely reliable) interrupted daisy chain upstream of and supplying
Ignition switch (Violet), by way of V Regulator and Fuse Block.


In the Amazon wiring, Ignition power is again supplied from the from Starter Motor Terminal 30, but it is routed by way of a single cable, with no other connections along the way…no terminals, no interruptions, no nuthin’…so there are no possible places for a less than perfect connection to occur and possibly affect the reliable power supply of the switch and Ignition!  See FIGURE 4.

FIGURE 4.  Amazon wiring diagram excerpt showing highly reliable uninterrupted wire supplying Ignition switch (Green),
single wire supplying Fuse Block (Orange) and daisy chaining only downstream of Ignition switch, actually Fuse 1 load side (Violet) . 


The Amazon also makes use of daisy chaining (but acceptably, in a less mission-critical area).  An example can be seen in the Ignition Power, Fuse 1 circuit (reference FIGURE 4), but the notable difference here is that the daisy chaining occurs on the downstream, load-side of the Ignition Switch (Fuse 1), so vehicle Ignition would be unaffected by connection issues, only downstream loads would be affected …one would still be able to make it home, just without blower or blinker! 

Downstream of the Ignition Switch of the Amazon, a heavy gauge wire leaves the load side of Fuse 1, and supplies the Wiper Switch.  A smaller gauge wire then runs off from there and supplies the Fuel Gauge, and the Fuel Gauge is also the tie-point where other wires star out to supply Blower, Blinkers, and OIL and AMP Indicators. 

The direct wire sourcing of the Amazon is clearly superior (see FIGURE 5)…because it is truly difficult to beat an uninterrupted wire for reliability!

FIGURE 5.  A comparison of the direct source wiring of the Ignition Switch of the Amazon model, with the indirect and potentially interruptible wiring of the 1800.  Besides the terminations at the ends (which both runs obviously have) specific additional areas of susceptibility unique to the 1800 design are highlighted…so it can be seen that an 1800 has 4 more potential areas of poor connection to disable Ignition than an Amazon!

Comparing Connector Types and Reliability

Connection Type

Cross Sectional Area

Reliability Level, Susceptibility to Corrosion

1.  Soldered

High, solder increases cross-sectional conductor area.

Max Rel. due to Gas-Tight_Joint, lowest susceptibility to corrosion.

2.  Stacked flat term

High, but still requires the compression force of fastener.

Hi Rel., but typically sub to eventual corrosion. 

3.  Push-On spring Term

Low, but high spring force makes it adequate for current up to 10 Amps

Med Rel, sub to corrosion as a function of spring-pressure, exposure to moisture and vibration.


Bottom Line (and my standard Mantra, if the reader hasn’t seen/heard it many times before…):  Keep the critical (at least) connections clean and snug!  1800 owners:  When in doubt, disconnect, clean, reconnect the four “special” terminals with ACZP…you’ll never regret having done that! 

Absolute minimum list of critical terminals which should be cleaned to shiny metal and treated with ACZP at reassembly (applies to 544, 122, 1800 models, at least):

Battery terminals (including chassis connection of Minus Terminal). 

Starter high current terminal (bolt with multiple ring terminals)

Ignition Switch terminals 30, 54

Fuseblock Fuses 1 & 2

Chassis strap (braided flat cable from engine to frame). 

Voltage Regulator (including chassis connection). 

Generator / Alternator (including chassis connection / mounting). 

Upgrading the 1800 Wiring, and putting it on Par with the Amazon:  If you have ever had an inexplicable Ignition failure in an 1800, or just want to loose this built-in weakness and improve your 1800 to give the maximum peace of mind and reliability level possible (and prevent a possible inexplicable Ignition failure in the future!), replace the two separate terminals in at VR and FB, with a single terminal, soldering both wires into each as shown in FIGURE 6.  Upgraded in this manner, the critical power connection to the Ignition cannot fail (even if those terminals vibrated completely off their connections at VR and FB and were hanging in the air like an FM antenna, the critical through-connection supplying the Ignition switch would remain in-tact!).  This will give the 1800 the same level of reliability of its Ignition system, viewed from a standpoint of power supply, as a 122.  I recommend it!

FIGURE 6.  Upgraded 1800 Ignition switch power wiring gives the highest Ignition reliability.  Note that areas of possible poor connection to VReg and FB remain, (method for minimizing connection issues on these are well covered elsewhere…see Mantra!), but poor connections in-line are totally eliminated from supply of Ignition switch with this upgrade, therefore Ignition itself has absolute highest reliability equal to an Amazon with its uninterrupted wire.


Related Links: 



This article is Copyright © 2010 by Ronald Kwas.  The terms Volvo and Lucas are used for reference only.  I have no affiliation with either company other than to try to keep the former’s vintage products working for me, give the later all the grief they deserve, and to help and encourage other enthusiasts do the same.  The information presented here comes from factory or my own wiring diagrams and is strictly my own experience and opinion, and can be used or not, or ridiculed and laughed, 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 don’t, you’re 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 maybe wise-a** comment. 


B A C K! ...to Tech Articles!