123GT FuseBlock Rework
Feb 2018  R. Kwas  Revisions on-going  [Additional Comments]


Fuse Allocation Tab (FB2)
Reference Information
    Fuseblock Core Notes



Key steps of the rework of a FuseBlock2 of the Volvo 123GT are shown (these are substantially the same as steps for rework of FB1[which is identical to FB fitted in a 122, and 12V544], but shown here to also highlight some of the unique features and differences in the FB2). 

Not shown, are specially developed tools and techniques...[I can't give away all my secrets!]

The observant reader may notice the words careful and carefully used here a number of times...this is not coincidental! 


123GT FB2 core, as received...frontview...not so pretty, but all there, so a good candidate for a rework! 


Rearview, with conductive commoning strap (unique to FB2 of the 123GT), which ties all source sides together, clearly evident on left.  (See also:  123GT FuseBlock 2  ).  Also evident are dirt and corrosion products of varying colors. 


FB at the drillpress, ready for separating terminals from base.


All rivets are carefully drilled out of the brittle Bakelite housing.  ...too much force, and Bakelite fractures!   FB is supported just right by a specially constructed wooden fixture. 


Brass terminals are carefully separated from the base.  Here, some are laid out for inspection...corrosion has worked it's way between all, especially the lower terminal. 

If it is not clear, from the pictures here, why these FBs require rework, here is link to discussion of the electrical reasons for which it is necessary: Gas-Tight-Joint  

Also, and particularly applicable to the 123GT FB2 because of the Alternator based Charging System, if the incoming power connection (output of the Alternator) ever were to become electrically open due to terminal corrosion, the system could be subjected to a load dump voltage surge, possibly resulting in damage to voltage sensitive components on the power buss (in the Alternator, or Radio, etc.).  This is addressed and explained further  here:  https://www.sw-em.com/123GT_Reliability_Weakness_and_Simple_Improvement.htm#Supporting_Info_Charging_Sys_and_Battery 


Intermediate Steps (not pictured):  

Terminals are strung onto a wire, and blasted clean with fine media. 

Bakelite base is carefully cleaned well! 

Cleaned Terminals are abraded to further clean solder surfaces, removing blasting media which gets embedded in the surface, and tinned using 60/40 electronic solder.

Note: The 60 refers to the lead content of the solder! ...but there is no need to over-react!

See:  https://www.sw-em.com/Wiring%20Notes.htm#Lead_Poisoning...Hogwash     


Cleaned components laid out in preparation for reassembly.  Terminals are clean, abraded in the area to be soldered, and not yet tinned.  Clearly apparent is the long brass commoning strap. 


Reassembled FB, before reflowing of the terminal hardware. Brass Hardware is evident.


Completed FB.  All terminals have been reflowed, simultaneous torquing, and solder added to fill the Phillips heads.  Frontview.


Rearview, showing additional solder from power input terminal screws to commoning strap for absolute minimum in-line resistance, and optimum monolithic gas-tight connection of all terminals.  Voltage drops occurring here will be at their absolute minimum, and for a very long time! because of the Gas-Tight-Joints!


Additional Steps:  

All exposed brass is coated in Deoxit D5 terminal Treatment.

Central threaded insert gets a dab of ACZP

FB Cover is replaced, if customer included it (not really necessary!), with the returned FB. 

Reworked FB is packaged, along with additional ACZP for optimum fuse installation, for return to customer. 


Fuse Allocation Tab (FB2):  

Once the FB2 is looking its best and functioning better (than new!), you might be interested in adding this little detail.  It's the Allocation Tab PN 672600, just inside the cover (similar to what the FB1 has!).

If the Fuseblock Cover of your 123GT is missing the cute little insert which identifies which fuse supplies which load, here is a graphic with which you can make a reproduction of the little chart. Note that both Euro and US additional Lighting versions are shown...select and make up the one for your language of your preference, appropriate for vehicle configuration!  Note also, that Fuse values vary with installed equipment! 

 Copy this file, import it into a document program like MS Word, enable the ruler function so that the surrounding octagon can be sized to 1 1/8" X 2 1/8" or 29mm X 54mm and print, preferably on the heaviest ivory card stock your printer can handle (and a preferably laser and not ink-jet), cut out on the octagon, punch a 1/8" hole in the center, treat the paper with a spray-on clear lacquer, and place on the threads of the FB Coverscrew. 

Reference picture is from  https://vintageswedishcars.com/ , Rolf Åström's page with the most comprehensive 123GT Spotters Guide I've seen!  Special thanks also for his help with the Swedish! 

Viola...just like new...and BTW, these are of course included in the reworked FB2s offered under the SW-EM Kits page!  [Plug!]


Reference Information: 

Link to:  Fuseblock Core Notes

123GT Wiring Diagram (Euro version):  https://www.sw-em.com/123GT-Wiring-Diagram_Euro.jpg

123GT Wiring Diagram (US version):  https://www.sw-em.com/123GT-Wiring-Diagram_US.jpg

Note:  Euro and US Wiring Diagrams have differences, but not in the FB1 or FB2 areas! 



Read about FuseBlock1 long-term weaknesses in 122, 123GT, also 12V544 vehicles, symptoms, and corrections, here:   https://www.sw-em.com/gastight.htm

If the reader is not in a position to perform the steps shown here, they could simply buy a reworked FB!  See:  https://www.sw-em.com/swemkits.htm#restored%20fuseblock  


This information is Copyright © 2021.  Ronald Kwas.   The term Volvo is used for reference only.  I have no affiliation with this company, other than to try to keep its 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 around the watercooler, 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 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 probably wise-a** comment. 


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