Courtesy Light 1800 Information and Notes
First published: Jan 2020  R. Kwas  (Updates on-going!)  [Comments Added!]

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Additional Complication...an Early vs. Late Switch Variation

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Fitted from '61 to '71 Sport Volvo Model 1800, the Interior Courtesy (also "Opera") Lights on C Pillar - used 3910 Festoon Base, 39mm bulbs.  LED replacements are available and work well in this application.  


 


1800 Courtesy Light with a nice white and bright LED Lamp installed. 

 

1800 Courtesy Light located on "C" pillar.  Local control, consisting of a Lens Switch, activated and closed to turn ON lights when the Lens is lifted slightly (irrespective of Dashboard Switch control!) to allow the two Red highlighted tabs to make contact to lamp fixture, which is electrically connected to vehicle chassis by mounting screws. 

 

Note:  Courtesy Lights located on "C" pillar are not to be confused with Map-Reading Lamp located under Dashboard, which is also a Battery powered circuit, but it has its own Switch. 


Volvo 1800 Courtesy Light Wiring.  Due to all the control options, a simple, but fairly involved circuit! The Violett wire which supplies Battery power from Fuse 1, also supplies Cigarette Lighter and Map-Reading Light, but these have their own separate controls. 

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Links: 

My response to Swedespeed Thread:  1964 S - Interior Light Won't Turn Off [Symptom:  Interior Light stuck ON after cleaning the interior.]  ( https://forums.swedespeed.com/showthread.php?614271-1964-S-Interior-Light-Won-t-Turn-Off&p=7496941#post7496941  )

There are three ways to control the Courtesy Lights in an 1800: With Switch under the Dashboard which either turns them (always) ON, OFF (center position) OR puts them under "door control" OR local to the Light Fixture itself (by lifting the bottom of lens away from the mount slightly, a contact is closed to turn them ON irrespective of the Dashboard Control or Doorswitches!)).

Many owners are not aware of this "Switch built into Lamp" covered in the Owners Manual/Instruction Book. I expect that in the process of "cleaning the interior", either the Switch under Dash (which you probably know about) was set up, to the ON position OR the Lens "local control" (which you would only know about if you RTFM) was inadvertently lifted to the ON position...

Reference Wiring Diagram (Items 48, 50): https://www.sw-em.com/1800%20Wiring%20Diagram.jpg
OR 1800 Instruction Book (my "65 book has it on page 10) Item 45.

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Reference Information:

RTFM Read The Freakin' Manual  ["from Manual:  45.  Switch for Interior Lighting (built into Lamp)."] 

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Variations in Factory Documentation:


An excerpt of the 1966 Instruktionsbok/Swedish Owner's Manual, clearly shows the two local switches included (45). 

 


The English Instruction Book/Owners Manual from 1967 clearly does not show these switches. 

 

In the later '71 1800E, the same Courtesy Lamps with local control are still used, and the Wiring Diagram has been improved to show the local switches as part of the fixture (shown in a common box!). 

Note also that Courtesy Light function of the early 1800s is that when EITHER door is opened, BOTH "C" pillar lights come ON, and for the later 1800E, function is different!  Drivers Door controls ONLY Drivers side Courtesy Light, and Pass Door ONLY controls Pass side Courtesy Light. 


Excerpt of '71 1800E Wiring Diagram, showing Courtesy Light circuit.

When looking closer at the '71E Wiring Diagram...it becomes clear that they saved a wire!  Earlier models had both Supply AND "Gnd to turn ON" circuit wires between the two fixtures, later E circuit had only the Supply wire running between the two fixtures, so earlier switching is not possible as it is wired in the E models...
BUT...if you want to retrofit earlier switching, you could simply run the second "Gnd to turn ON" wire between the two fixtures and viola!...everything is doable!...we have the technology!...AND you could ADD a lamp of a couple of Watts, located under the Dash onto this circuit ...I was never very impressed by the footwell lighting in the 1800 (as in none!), when you open the doors...more Lucas automotive electrical non-wizardry?

 

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Additional Complication...an Early vs. Late Switch Variation!

If the previous variations in the Courtesy Light circuitry of the 1800 are not complicated and confusing enough for the reader, read on...! 

Volvo apparently had complains about glare at night, from the excessive bright OD and Hi-Beam Indicators of the later, blackface instrumentation, so they decided to add a Dimmer Switch in the late production 1800s...and where did they locate this switch?  Answer:  They removed that three-position Courtesy Light Switch completely from the circuit, leaving it under Door (and local) control, with manual ON selection at the ceiling mounted Courtesy Light fixture (similar to 140s) from the driver position possible, and used the available location on the little Vent Control Panel, for the two position Dimmer Switch!! 

 


Excerpt from the '73 ES Operator Manual.  Location of (two position!) Dimmer Switch is on Vent Control Panel under Dashboard
...but only on 1800ESs!  Setting the switch into the UP position, dims the two indicators when ON, by adding
a resistance in each lamp current paths to chassis.  

 


'73 1800ES Wiring Diagram excerpt for Dimmer Switch and associated wiring.  I expect the two Resistors shown in the switch to have an R value somewhere under 100Ohms.  When placed in series with the two indicators, they decrease the current and so dim the lamps to a non-glaring level. 
[An owner who has this resistance value handy, or can measure it, is invited to forward this info to the author, so it can be included here.]
 

Note:  The Dimmer Switch is not present in the '71 1800E Wiring Diagram excerpt '71 1800E Wiring Diagram excerpt above! 

If uncertain how a vehicle is configured, the certain way it can be simply determined what the switch function is, by checking the number of switch positions...two positions is the early, Courtesy Light Control, and three positions it is the Dimmer Switch

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External material sources are attributed.  Otherwise, this article is Copyright © 2020.  Ronald Kwas.  The term Volvo, is used for reference only.  I have no affiliation with this company other than to present my experience, and highly opinionated results of the use and care of their products, for the purpose of helping other owners keep their vehicles on the road, safe and reliable.  ...and I sure as hell don't have any relationship with Lucas, except to give the all the grief they so fully deserve (see for instance:  Proving Everything Bad you Ever Heard About Lucas).  The information presented is my own, and can be used or not, or ridiculed and laughed at, or worshipped, 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, and future! 

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 Sw-Em site as the source.  If you don’t, you’re just a lazy, scum sucking plagiarist…so 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. 

 

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