123GT Reliability Weakness and Simple Improvement  
Jun 2016 R. Kwas, changes on-going [Comments added]

See also:  SW-EM Tech Bulletin Number 5!

Recently, a 123GT owner decided to install the SW-EM Alternator Upgrade (first time ever that such a conversion was done...this is rare as the GT already has an Alternator, although its a weaker 30A Motorola with mechanical regulator!).  So while this is not a common occurrence, it is understandable for the known advantages, and while carefully considering details of this change, and reviewing the wiring involved, I noticed a weakness unique to the 123GT Model.  This article is intended to explain the weakness and present a simple improvement to address and eliminate it!  


123GT FuseBlock 2
Supporting Information:  Charging System and Battery, including Load Dump Surge


Background:   On Alternator equipped 123GT vehicles, output of the Alt is directly routed to Fuseblock 2, connected there by way of a push-on 1/4" connector.  Fuseblock 2 fuses supply Lighting and Horn circuits.  Another wire, also connected by way of a 1/4" push-on terminal, then routes the Alt output to the typical Battery tie-point at the bolted connection at Starter Solenoid (Terminal 30).  

Fuseblock 2 on the small electrical panel on inner fender of the 123GT model.  2 push-on terminals of interest are highlighted in Blue on the power input side of Fuseblock. In this picture of a RHD, a mechanical Voltage Regulator is visible to the left.
Compliments on a nice, clean engine compartment and picture credit to Ross S.

Electrical panel with Fuseblock 2 on a LHD 123GT.  
2 push-on terminals of interest are highlighted in Blue on the power input side of Fuseblock.  An electronic Voltage Regulator is visible to the right.
Also a spotless engine compartment  and picture credit to Rolf A. at Vintageswedishcars.com 


Volvo did recognize the importance of not disconnecting the Alt output from the Battery, and felt it important enough to add a warning sticker on the underside of hood...again, the original design and construction is fine, but 50 years later, as looseness or poor connections due to corrosion develop (as we know they can!), the possibility of disconnection becomes greater, so needs to be checked for and prevented.

Alternator warning label as affixed to under the Hood.


It is therefore recommended to check the two push-on terminals highlighted above for looseness on the Fuseblock terminals and / or corrosion!  At the very least, cleaning them and reconnecting while protecting with a bit of ACZP.

While push-on terminals are generally highly reliable (Reference:  The Lowly 1/4" Terminal), the rated 30-35A output of the OE Alternator is about their safe limit when clean and snug.  It is also a fact that 1/4" push-on terminals can be easily removed, and in some cases, have been known under certain environmental conditions, to become loose or develop poor or intermittent connections due to corrosion over time. The connection issues can also occur within the FB (See also:  123GT FuseBlock Rework  ).  In the case of that happening on the Alt output line using those terminals, that would result in the Alternator going to an unloaded output condition.  This is particularly bad and should very much be prevented(!), and this becomes even more of a concern when increasing the currents which these connections may need to pass with an upgraded Delco Alternator!

123GT Wiring Diagram excerpt with wiring area of concern Highlighted in Red.


Supporting information:  General explanation of Alternator Charging System function, and why disconnecting the Battery intentionally or allowing it to happen inadvertently is just not a good idea...in fact, this is BAAAAD!  

The Electrical System of a car is called a System for a good reason.  The Voltage Reference in the Regulator, controlling the Alternator output, in combination with the Battery chemistry, keep the System Voltage at a fairly steady operating point.  Clearly, they need to be tied together for this, because while the Alternator output powers everything when engine is running, it doesn't put out a clean DC (more on this in (3.) below).  After (1.) Starting (obviously its' first duty), the Battery actually serves several important functions (even when not at its' best!), so must remain connected to Alternator output at all times

2.  Battery Smoothes the system Voltage which might Dip as a result of a Load being turned ON, or Spike up (Surge) as a result of a Load being turned OFF.   A momentary Dip is not such a big deal if it were to occur, but a Spike or Surge during Load Dump, not clamped and limited because the Battery was not connected (or only connected poorly through a less than good connection), can overstress components in the Alternator or elsewhere (similar to home electrical systems where Surge Protectors to protect against this are common).  This is less of an issue with older cars which were more tolerant of power system inconsistencies because they didn't have Injection Computers, or other sensitive control electronics, but there are certainly "electronic" components for instance in the Voltage Regulator and the Radio of vintage cars...  Disconnecting the Battery would remove this smoothing function during Voltage Transients, so it is not advisable, even only momentarily or for purposes of "test" (also a BAD Idea!...more on this below also!).    

Some numbers: 

This is what System Voltage could look like, if Battery was disconnected (author's Highlights)...say goodbye to voltage sensitive components(!), including Voltage Regulator, Stereo, possibly even Lamps!  This is an excerpt from EETimes on-line ( http://www.eetimes.com/document.asp?doc_id=1273228 ). 

3.  ...but we're not done with the important functions the Battery provides!  It also Filters the current pulses being generated by the three-phase output of the Alternator.  Yes, an Alternator generates DC, but that is a simplification...more correctly, it generates sinusoidal AC, which is then rectified and turned into a "pulsed" DC, and the Battery again smoothes (filters) these pulses so that the vehicle's Power Buss has a true DC voltage with little variation.

Alternator Voltage Waveforms, from Alternator Output, to (Battery) Filtered Power Buss.


Having accepted that intentionally or unintentionally disconnecting components of this system is just not a good idea!, we want to also minimize the possibility of this happening inadvertently.  It is for this reason, that I consider the push-on terminals (normally a highly reliable connection) in-line with the Alternator output at the Fuseblock 2, to be a less than acceptable for the possible large currents flowing, and based on this, the following improvement is presented: 

By connecting both incoming and outgoing wires together in a single, common 1/4" push-on terminal crimp (soldered terminal would be even better *) , then connecting this single push-on terminal to the Fuseblock 2, all of the potentially weak connections are taken out of the series path!   This recommended fix is quite simple but effective, and it will prevent an inadvertent disconnection (including momentary) of the Alt output from the Battery.

Ron's Rule:  "When I want the best crimped connection, I solder it!", because nothing beats a Gas-Tight-Joint!  See also:  http://www.sw-em.com/emergflash.htm#making_in_line_connections


Recommended reliability improvement shown in Green. 


The wiring so changed, would assure that even if the 1/4" push-on terminal was to develop a poor connection, OR inadvertently get dislodged or pulled off, OR the riveted Fuseblock 2 connections, known to develop corrosion and connection issues (See below!), may open, but the important connection to Battery would not!  Note that the recommended improvement does not require modifying any other components, but optimally, it should be used in combination with a SW-EM rebuilt, fully soldered, Fuseblock 2. 


As an example, riveted terminals of Fuseblock (1) disassembled, showing inter-stack corrosion. 
From Gas-Tight-Joint Tech Article. 



Before:  When connected in the original equipment configuration, six potential sources of poor connections are in line with Alternator output to Battery path, which might over time allow disconnection of Battery from Alternator...these are:  Crimp 1, 1/4" terminal 1, riveted internal Fuseblock connection (2), 1/4" terminal 2, and Crimp 2.  A poor connection on any one or more of the locations would lead to Resistance Heating, and a fully open connection (even only momentary) can lead to system Voltage transients resulting in Alternator or other electrical component damage.   

After / Improved:  When modified as recommended and connected , all six potential sources of poor connections in line are eliminated, because Battery current no longer flows through FB2. 

123GT Charging System Wiring Before, and After/Improved!  Charging current path shown in Blue.  
It doesn't look like much of a change, and it isn't, but would make a huge reliability improvement under certain possible failure conditions which are more likely to occur the older vehicle gets!


Implementation:  Putting two 6mm2 (10ga.) wires into a yellow crimp intended for one 10-12ga is just not possible...larger crimps to accept two 10ga wires are available, but may be difficult to find.   Another option is to modify a yellow crimp to accept two 10ga wires.  After doing so, I was able to insert and solder then to make a somewhat unique connector.  Admittedly, a lot of work for two lousy wires...but as explained above, there is good reason and justification for this!  I did this on the bench with a high quality yellow crimp as an example:   


Insulator and outer barrel of crimp are sliced and removed. 

Crimp is splayed opened to increase OD of wire it will accept. 

Two 10ga. conductors, which would normally be oversized for an unmodified crimp barrel, are twisted together and now fit. 

Conductors are soldered into crimp barrel using solder with leaded goodness (do not eat!). 
Heat-shrink tubing (or two pieces, applied to wire before installing crimp!), would then be slid over crimp barrel and heated. 
Gas-Tight-Joint is then complete and ready to connect to FB2 with ACZP...yeah, a lot of work, but a soldered joint does not deteriorate the way a crimped joint can, so this is necessary only once in the life of the car. 


Excerpt from and e-Mail to Andrew C. regarding this issue:  "That minor mod at the Fuseblock is not a huge deal...it only addresses what I would consider to be a pretty rare and only remotely possible failure condition, but because its so simple and easy to incorporate...why not?"


Reference Information: 

Copied from:  http://www.dslreports.com/forum/r25224580-Q-about-engine-running-with-dead-or-disconnected-battery

Good answer to question about running an alt without battery connected:



From:  http://www.bcae1.com/charging.htm  (in addition to much other good information for the interested).


UPDATE 2024:  I have now engineered and incorporated the above improvement into the Alternator Conversion Kit when installed into the 123GT!   



External material is attributed.   Otherwise this information is Copyright 2016-2024 Ronald Kwas.  The terms Volvo, Motorola and Delco are used for reference only.  I have no affiliation with any of these companies, other than to try to keep their products working for me, and to help other enthusiasts to do the same.  The results and information presented here are my own experience, and carefully considered opinion, and can be used or ridiculed as you see fit.  As always, if you can supply additional objective info or practical experience, Id appreciate hearing it, and will consider working it in to the next rewrite of this article...along quite possibly with the odd wise-a** comment, if I can possibly work that in. 

You are welcome to use the information here in good health, and for your own noncommercial 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 dont, youre just a lazy, scum sucking plagiarist...so the Washington Post wants you! 

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