Headlight Notes   
Dec 2020 R. Kwas   [Comments Added]


These notes are intended to cover Headlight Control and Additional Lighting, like Fog or Spot/Driving Lighting.  

Note:  This new article contains previously covered material, but I have added new material, consolidated, and cleaned it up and tried to present it better and more easily followable. 

If the reader is considering Lighting changes and improvements, they should have a look also at Lighting Notes, Including Upgrades...I will leave the older tech articles posted, but I expect to eventually consolidate all the separate articles in to one place.


It doesn't look like Steven Kraft is going to "overdrive his lights" any time soon!
Picture posted with his kind permission.



Level 1 Relay for Headlight Signaling
Level 2 Control of Headlights with Bistable Relay
    Control of Headlights with Bistable Relay on an 1800
Adding Fog or Spot/Driving Lights

    Additional Fog Lighting

Stabilizers for Additional Lighting

Reference Information
    Bistable Control Relay
    Sealed Beam Headlights Information

    H3 Dimensional Specifications


There are two+ Levels of changes possible to the vintage Volvo Forward Lighting.  The changes covered here can be made on 544 and 1800 vehicles as well, with the appropriate variation in harness and details.  The 122 wiring is shown here as an example.  Added:  Control of Headlights with Bistable Relay on an 1800.   

Reference 122 Wiring Diagram:  https://www.sw-em.com/122S%20Wiring%20Diagram.jpg

Level 1.  The "Relay for Headlight Signaling" as shown in the factory Wiring Diagram can be restored and added back into place, so this cannot rightly be called an "upgrade".  This relay was not (allowed to be!) installed in the US...if a US driver wanted to flash their Headlights to signal another driver, they couldn't simply pull back on the Directional Stalk like drivers elsewhere in the world could...this Stalk position was without function in the US!...the brainacs at the USDOT made drivers move their hand from the Steering Wheel and activate the Lightswitch! 

Level of difficulty:  Quite Simple!...required wiring (Red, Grey and Black) is in place in all harnesses, so (re)activation of this function is a simple matter of adding the RfHS back in at the relay area in engine compartment (a simple 3 Terminal relay will do, since the Coil power is also the Load power!), locating the wires (which are present, but tucked into harness and unused), and making the relay connections.   

Explanation of Circuit Function:  Power for RfHS is supplied by Black wire from Fuse 4 (8A).  Grey wire from momentary grounding contact at Directional Stalk (or as Volvo calls it on the WD "Flasher Mechanism for Headlamp Signaling") completes circuit to chassis for relay coil which closes working contact of relay, and applies power to Red wires (Hibeam circuit).  Hibeam circuit is energized for as long as Stalk is pulled back, and since power is taken from a Battery (continuously) powered Fuse 4, this function is available any time, even when Ign is OFF.   


The Green highlighted "Relay for Headlight Signaling" is added and function is restored with existing Green highlighted wiring, as it is shown in this excerpt of the factory 122 Wiring Diagram.  Notice the RfHS is simply in parallel with the "Foot Dipper Switch" (either component can apply power to the Red wire (Hibeam circuit) . 

After making this change and restoring the Headlight Flashing Function, a vintage Volvo will have the same feature this model had in parts of the world, other than the US, when it was originally produced. 


Level 2.  Upgrade to a modern Directional Stalk Control of Headlights with Bistable Relay.  This would bring the 122 Headlight control system to even more modern state than it ever had from the factory, so can rightly be called and "upgrade".  This change requires installing a Bistable Headlight Control Relay (same as fitted to 140 and later models) in the relay area, also using the existing wiring (Grey and Black) to activate it, but it also requires relocating the wires of the OE "Foot Dipper Switch", to the new BHCR in engine compartment, so it can do the Hibeam/Lobeam switching when Headlight Switch is ON.  The Momentary Hibeam flash (anytime) is also handled by a momentary contact in the BHCR

Note:  When adding the BHCR, it is not possible to also keep the Foot Dipper Switch, and have both connected and able to function, so this is truly a conversion from Footswitch to Stalk control.  [...and for my Amazon owning friends in foreign lands, where the Relay for Headlight Signaling may have been fitted, but who now want to upgrade to a BHCR, the RfHS must be removed also!]

Level of Difficulty:  A bit more involved, but still a Saturday morning project. 

Explanation of Circuit Function:  Power for BHCR and Momentary Hibeam flash function is again provided by Fuse 4 (8A). 

Momentary function (Headlight Signaling):  Directional Stalk can be pulled back activating BHCR any time (including when Ignition or Headlights are OFF), relay is activated, and power is applied to Red wires (Hibeams circuit) by way of momentary contact 56a. 

Hibeam/Lobeam Control Function:  When Headlight Switch is turned ON, Headlights (Hi/Lobeams) are in the last position they were left in when Light Switch was turned OFF.  When Directional Indicator Stalk is pulled, Hibeams are activated for as long as Stalk is pulled back, and when released, bistable contact drops to terminal 56a (Hibeams), or 56b (Lobeams) alternately, and remains stably there until next time relay coil is powered, at which time it drops to the alternate contact, and remains there stably.  This toggling function, and stability in two positions gives the Bistable Relay its common name.  In the "Foot Dipper Switch" the toggling function was mechanical, in the Bistable Relay, toggling function is electro-mechanical.   

Red is IN, Yellow is OUT or Disconnected in this marked-up excerpt of factory Wiring Diagram.  Red highlighted Bistable Headlight Control Relay is installed using wiring which was formerly intended to control the Relay for Headlight Signaling (Gray Wire), and  "Foot Dipper Switch" is removed. 

Control of Headlights with Bistable Relay on an 1800.

Red is IN, Yellow is OUT or Disconnected in this marked-up excerpt of factory Wiring Diagram.  Red highlighted Bistable Headlight Control Relay is installed using wiring which was formerly intended to control the Relay for Headlight Signaling (Violett-Brun Wire), and "Foot Dipper Switch (Fotomkopplare) is removed" 

Adding Fog or Spot/Driving Lights

Whether trying to make it safely down a foggy interstate, or bombing down dark Swedish woods as in this picture by Rick Watson,
additional lighting to address the very different and special requirements of either, will allow you to see where you're going! 
In this picture, it looks like he has both Fogs (Orn) and Driving lights (Grn) ON for MAXIMUM Lighting!
R. Watson picture used with his kind permission.

Add-On Fog Lights Notes: 

Lighting pattern and Adjustment of Additional Fog Lights should be low, to minimize blinding reflections,
and to the sides, to illuminate road side-markings and signage (and suicidal wildlife!), as seen above in (Orn).


Additional Rear-Mounted Diffuse Red can be added to increase visibility for those following.  I realize this is the Headlights Notes page, but this still seemed the best place to add these rear-facing lighting improvements.  Some examples follow. 

See also Additional Fog Lighting below.

Picture by H.-D. Kleine of the Volvoniacs Forum and used with his kind permission. Picture by Christoph W. also of the Volvoniacs Forum, and used with his kind permission. In order to clear the Tailgate swing, the Rear Foglight is located below Bumper on this Amazon Kombi, and in order to leave it less vulnerable to attack by parking barriers, it is also rectangular, and no lower than Exhaust Tip!


This British owner has added dual Rear Foglights and a raised Third Brake Light, for maximum visibility to those following. 
Also shown are the DQBVVATS (Dual Quadraped Biological Vintage Volvo Anti-Theft System)! 
Jayne Berry pictures used with her kind permission.


How would you rather like to look, if you must be out and about on some foggy night...?

Like this? ...or like this?

Add-On Driving or Spot lights Notes:  

Lighting pattern and adjustment of Driving or Spot Lighting (also "Pencil Beam") is straight out front,
 as seen above in (Grn), such that even if you were at terminal velocity on the Mulsanne Straight,
you would still be able to see further than your braking distance!


Add-on lighting can be wired with completely separate circuits, with separate Dashboard controls for each circuit, allowing driver to power any combination of OE plus additional lighting, OR wired combined with the standard Hi and Lobeams such that switching becomes automatic and slaved to the Bistable Headlight Control Relay (by taking the power to the controlling relays from the Hi and Lobeam circuits).  If combined, Fog Lights should be wired to be enabled with Lobeams, and Spot/Driving Lights should be wired to be enabled when Hibeams are ON [...one wouldn't want it the other way around, take my word!].  This automates the switching such than the driver can simply switch between Hi (plus Spot/Driving lights option), or Lo (plus Fog lights option), and this functionality is actually required by Euro-Regulation.   

Be aware that the Wattage required for Additional lighting will result of a total additional load current (of 9Amps for two 55Watt elements for example) on the electrical system, so should only be considered after increasing the Charging System nominal output.  An aging OE Bosch 30A generator does not have the output margin, especially at low RPMs, to run the Ignition, normal lights, and general loads, plus the additional lighting load.  If additional lighting were installed without uprating the Charging System, Battery would have to contribute energy and would be being discharged whenever the additional lighting was ON...not a good situation!  If the reader is considering additional lighting, an Alternator upgrade should be included in the plan!  


Suggested Fog/Spot Light Control Wiring with automatic switching. Again, Red is IN, Yellow is OUT or Disconnected,
and Green and Blue have been added in this marked-up excerpt of factory Wiring Diagram. "Lo-beam Power" (56b)
also enables Fog Relay control, and "Hi-beam Power" (56a) also enables Spot Relay control,
when their respective Dashboard control switches are ON. 
Power for additional Lighting should be by a fused Ignition Power source...like the Ignition Slave Relay.  


Note also, automated control can come from OE "Foot Dipper Switch" in Level 1 diagram above, OR "Bistable Headlight Control Relay" (56b), so the automatic switching can still be incorporated at Level 1 without a BHCR.


Additional Fog Lighting: 

Suggested Foglight Control Wiring.  The control circuit shown here,  includes the optional Rear Fog Light for
improved visibility by those following!  If the Rear Fog Light is a low-current-drawing LED, one could even forego the Relay!

Additional Spot/Driving lights:  Similar to Foglight control wiring above, but replace "Lobeam Power" in the drawing, with Hibeam Power (56a), omit Rear Relay, and Light, and connect Dashboard Indicator in parallel with Lights. 

Stabilizers for Additional Lighting: 

Steady/Stay Bars for additional calming of  "Foglight-Parkinsons"! 

Bouncing Lights?  Sometimes the mounting of Fog or Spot additional lighting results in physical properties of their mass and mounts, such that resonances occur with what is essentially an "overhanging mass", because of the single support.  When this occurs, the light from them can bounce or flicker annoyingly, severely detracting from their usefulness! 

Several styles of steady bar linkages are available for connecting between top/back of the Lights (additional hole(s) will be necessary!) to the solid structure of the nose, these will give a second mechanical support and (usually!) put and end to these resonances.  Some variations are shown here. 


Picture source:  https://www.merlinmotorsport.co.uk/p/adjustable-lamp-steady-bars-pair-ge56 Available from Biltema, the Swedish automotive supplier:


Pictures of steady bars installed on some serious rallye Volvos: 

https://www.sparelch.de/  Marc S.

Knut G. picture used with his kind permission.


Constant Busch pictures used with his kind permission. 


Reference Information: 

Link to Tech Article:  Comparing 3, 4 and 5 terminal Relays:  https://www.sw-em.com/Ignition_Slave_Relay.htm#comparing_3_4_and_5_terminal_relays

Bistable Control Relay (Volvo Part No. 1307991, supplied by HELLA, SWF and other manufacturers).  These are quite common, having been used on the 140s for Headlight control, some 1800s for Overdrive control, and later Volvo models, also for Headlight control, so they are readily available new and used.  Before installing a used Bistable Relay, an internal inspection of the condition of the contacts and lubing the mechanical workings, is good practice!   

Bistable Relay, (HELLA version, [to be confirmed!]) internal view.  Teeter-totter toggling mechanism is apparent, as is Red Synthgrease I have applied to it.

A used Bistable Relay was recently obtained and inspected for possible reuse: 

SWF version PN R 200 836 and SWF logo are clearly apparent on the underside. 

SWF R 200 836


After cleaning off the engine compartment grime of 40 years, the securing tabs on the alu can were gently bent open to allow removal of the internal assembly for inspection.  This example is in very decent condition evidenced by the limited pitting visible at Green highlighted Momentary (M) contact to the right of their teeter-totter mechanism highlighted in Orange.  Since this contact is commoned with one of the other bistable contacts (1) at Blue, and is clearly ONLY closed while the relay is under power and "picked", it can be deduced that these are the Hi-Beam contacts.  The lone Yellow highlighted bistable contact (2) and its terminal are therefore the Lo-Beam output. 


A close-up look at the (open) Lo-Beam contact (2) shows remarkably little (actually zero!) wear or erosion, and the generally stout mechanical construction!  This finding also suggests pretty undeniably that this Relay was probably used not in Headlight control, but in OD service, where only the Blue contact (1) would be in service.  This SWF version of the Bistable Relay gets two thumbs up (and OK to reuse!) from the SW-EM Hipshot Quality Evaluation Department (SW-EM HQED)! 


The teeter-totter mechanism will again be lubed with a dab of Red Synthgrease, the relay reassembled into its cleaned and polished can, and this little electromechanical marvel is approved by the Swedish-Embassy Restoration and Refurbishment Center (SW-EM RRC) for return to active service, controlling either Headlights OR an Overdrive Solenoid (Link: OD Wiring 2)



Bistable Relay Volvo Part No. 1307991, terminal view. 

Note:  It is not necessary to have an electrical connection to chassis for relay to function...coil is isolated from enclosure, and this can be simply confirmed with a continuity test. 


Sealed Beam Headlights Information:


H3 Dimensional Specifications: 

Source HELLA Website:

The Critical Dimension highlighted is at the heart of the problem, why installing LED replacements is not a simple matter...if the light emitter(s) are not located at this precise point in space (and more importantly, the reflector!) they will not play correctly with it.  This is critical for Headlights or Taillights!  See also:  https://www.sw-em.com/Amazon_Rear_Light_Fixture_Restoration.htm#Considering_LED_Replacement_Lamps  


Light Socket Information:  

German Version of the popular reference site at:  https://de.wikipedia.org/wiki/Lampensockel  is far superior, with much more comprehensive data as well as cross-referencing, than the English version:  https://en.wikipedia.org/wiki/Lightbulb_socket  ...why is that?...maybe I'm just not looking in the right place...! 


Links to other SW-EM Articles on Lighting:

Not to get unnecessarily more complex, but Fog and Spot/Driving Light control of the 123GT model has the automatic switching/enabling already built in, and is different from the US to the Euro wiring!  This is covered separately here:  123GT Consideration of Lighting Differences







External material sources are attributed.  Otherwise, this article is Copyright © 2021.  Ronald Kwas.   The terms Volvo, HELLA, SWF, and other manufacturers or suppliers, are used for reference only.  I have no affiliation with any of these companies other than to try to keep their automotive electrical products working for me, help other enthusiasts do the same, and also present my highly opinionated results of the use of their products here (like giving Lucas all the grief they so richly deserve!).  The information presented comes from my own experience and carefully considered opinion, 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! 

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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