The Gas-Tight-Joint, Part II, Lucas works (dark) magic on the 1800.      

R.Kwas  Originally published 12/02  updated continually (Comments Added)

As it says above the SwEm kits, they were typically developed as a result of my own since I replaced the triple fuses on my '66 1800 with a 9 fuse fuseblock out of a 140 (see below), when I first recommissioned the car, I had never run into many of those strange, inexplicable electrical "gremlins" which are known to bother many early 1800 owners.  Sure, I had heard of them, and just figured they were built into the car courtesy of Lucas supplied equipment, and this was correct, but as I didn't have the OE fuseblocks which apparently cause a lot of the problems, I never had the need to get to the bottom of their cause myself, and so I never developed any information or upgrades.  I wasn't completely spared from the curse of English electrics...I also have had a "generous tachometer" * and non-working switches, and I even remember an "Inexplicable Lucas Incident" occurring on Wendy's black 1800...a sudden death of the car while she was driving, which miraculously cured itself before I came to troubleshoot and retrieve the car.     

After a number of requests by owners to look into the weaknesses of the early 1800 electrical system, and further requests for possible improvements or upgrades similar to the beloved reworked 122 Fuseblock, I finally looked into it.  What I found was pretty disappointing! 


Here is the statement which I include (or used to) with SwEm alternator kits going to 1800 owners:

[For 1800s, a thorough cleanup (after battery disconnection) of the fusebox connections and Anti-Corrosive Zinc Paste treatment is at least called for.]

Picture 1.  After clean-up and application of anti-corrosive paste
...much better!  ...and probably half of all 1800  electrical problems
 cured and prevented! 

[This is true, but no longer good enough, because in order to do "a thorough cleanup", disassembly of the fuseblock is necessary!

Now, after a much closer examination, I have to say:  I'm sorry, but I gave Lucas too much credit...the original design is totally inadequate in the long term (apparently defined by them as beyond 5 years...the blink of a headlight in Volvo terms!).  By comparison, surface corrosion will compromise the connections a lot sooner than those of the original 122 fuseblock!  This leads me to reaffirm my contempt for Lucas, for their - ehem - design.

Specifically, the fuseblock terminals on a 122 are held together with the well known rivet design (see: GTJ **), which applies a decent pressure holding a large flat area of the contacts together with the fairly high force required to deform the rivet metal into it's final holding OK design, generally lasting for a good number of years until corrosion develops between the contacts.  Before I disassembled an 1800 fuseblock for a close inspection, I thought surely the terminals, including those ridiculous little fuse holding/contacting clips were one piece, but nooooooooooooooo! 

 OE 1800 Fuseblocks.  Lucas technical aberrations!

They are two separate pieces(!), and what's worse is that the Lucas design, uses nothing more than the strictly incidental force of a couple of bent over tabs occurring as a byproduct of holding the two separate terminals onto the plastic base...the actual contact area for current to pass through is quite small, and the spring force from that little clip is really the design relies on strictly an absolutely clean contact on the fuse and the terminal.

This design is begging for improvement.  So in keeping with the SwEm long-term fix philosophy of vintage Volvo electricals, and feeling sorry for the other 1800 owners out there, I have figured out the ultra-reliable, super-groovy repair-upgrade for the two fuseblocks onboard.  After the main terminal is modified to accept a new contact, those ridiculous little original fuseclips are replaced with full-size, standard industrial fuse contacts which have enough spring-force to hold - and contact - the fuse with authority!  The assembly is then soldered a Gas-Tight-Joint joins the two pieces into one for - dare I say - EVER!  Installation of the fuse with anti-corrosive paste completes upgrade with Jacque Cousteau approved GTJ practice!

SwEm (half!) reworked/upgraded 1800 fuseblock. 

The bottom line, and my recommendation:  All OE early 1800 fuseblocks, both the single and double fuse units (as shown above, using the 3AG fuses, located under the hood, at the "left-hand wheel arch") should be replaced with upgraded units.  These are available now.

Symptoms?  Heating of the connections in the fuseblock area, from the crimp terminals to the fuse itself indicate resistance heating is taking place (Ohms law at work!)...the worse the connection the more heat is generated.  When properly designed and built, intentional resistance heating is a perfectly acceptable way to make in a toaster, but when it occurs unintentionally in a car's electrical system, it can lead to smoldering connections or insulation...or much worse!  See Brickboard posting of symptoms.

Inexplicable failures (including intermittent) of more than one at a time, of ANY of the loads which are "protected" by one of the three fuses onboard (see below), are a good indication that the fuse holder is suffering from excessive corrosion problems.  Inspecting and thereby disturbing the (unblown) fuse in question may very well restore function of the load(s), but for how long is strictly a crapshoot and known only to Joseph Lucas (who is probably, as they say:  Rolling in hysterics in his grave...I hope he gets gravel burns!)  


The extent to which your 1800 suffers from this problem can be checked by:
Testing with a Multimeter.
  Locate the double fuseblock, and without disturbing the fuses or connectors, remove the cover.  With a Multimeter set on a low voltage range (engine idling), measure the maximum voltage drop - under load - across the entire fuseblock assembly by probing across the push-on terminals of the fuseblocks (see below).  Do not measure across the fuse only, as this will not show additional voltage drop due to fuseblock resistance.

Measure the Battery Power (Brown and Purple wires) and Ignition Power (Green and White wires ) fuses one at a time.  In order to assure a high load current is flowing in each circuit while measuring, turn on lighter while measuring Battery power fuse, and blower and wipers while measuring Ignition power fuse.  I have yet to do this and get a representative maximum Vdrop number, but as an estimate, I would say anything above 0.3V is too much...naturally if your lucky enough to catch an inexplicable fallout of your electrical loads caused by an open fuseblock, you would read 12V across the totally open you would if the fuse was blown open.

 Resistance measurement of Fuseblock on bench (measurement shown is unacceptably high!) 
For in-situ, power-up Voltage drop measurements, Multimeter would be set on DC Volts and
probes would be connected also as shown. 

As a reference, an from the Ohms Law calculation V = I x R,  if a current of 10A (not an unreasonable operating current, given the load consolidation necessary when the vehicle only has 3 Fuses anyway!!) is flowing through a Fuse and Fuseholder resistance, 1 Volt (a value fast approaching unacceptable!) would be lost to a series resistance totaling a mere 0.1 Ohm!!


Refer to:   1800 Wiring Diagram  ...also Fuse allocation on the 1800 model

Battery Power Fuse (35A) Loads:  Horn, brights flasher, all courtesy lighting, lighter.

Ignition Power Fuse (35A) Loads:  Wipers, brake lights, Instruments, backing lights, heater blower.

Parking Lights Fuse (35A) Loads:  Parking Lights.  [???  The casual reader might wonder about those values, as has the writer!  It's a result of more Lucas (dark) magic!  Change your Fuse 3 value! kidding, and this is not a drill!  See:  ]

Note:  Being considered a mission critical load, the headlights are not protected by any fuse.  Problems with headlights are NOT indicative of Fuseblock problems.  Something else is amiss (and those "bullet" connectors are sure a good place to start looking!) . 

I also recommend AGAINST replacement with the factory new units I see available (new junk is still junk!), because the design is always doomed to intermittency.

In the worst case, leaving an old one fuseblock in place can possibly result in an electrical fire, and since the heat generated by a marginal connection is a function of the current passed, the upgrade recommendation especially applies to those owners who have installed alt upgrade kits and whose electrical system is now capable of passing increased currents. 

I consider this important enough to make it the subject of a Tech Bulletin.  And from this day forward, I will also highly recommend the installation of these reworked fuseblocks as an important part of doing an alternator upgrade on an 1800.

As far as that "Inexplicable Lucas Incident" occurring on Wendy's black will remain inexplicable, since the ignition is not powered by the fused circuit either, and it never failed when I was around, or ever again for that matter... it's a good thing...'cause I don't play well with "inexplicable".

Consider this a Recall Notice, not from Volvo but from a vintage Volvo friend at the Swedish Embassy! 


References, Notes and Links:

*  Link to Service Notes:  Generous 1800 Tachometer.  

**  Link to: Gas-Tight-Joint tech article.

  Upgraded 1800 fuseblocks are available now: SwEm Kits Upgraded 1800 Fuseblocks.

  Link to:  Lucas... RIP  "A gentleman does not motor about after dark."  Joseph Lucas (1842 - 1903).  Wise words from someone supplying highly questionable automotive electrical components, better known for crumbling, than controlling electricity.  With 2003 being the 100th anniversary of the death of Joseph Lucas, I wonder if anyone is going to have a special event celebrating this, other than to try to keep their lights working consistently and predictably for one entire year.

Attention:  All pre-'69 P1800 Owners:  Replace Fuse 3, specified at 35A, with an 8 or 10Amp rated fuse (Type 3AG)!


A totally different Solution...or Lucas?  No thanks!

All the info presented here is well and good but it doesn't address the silliness of why an 1800 only has three fuses in the first place!  [and then to specify one of them at a ridiculous, and useless, high value, see:   ]

As I stated at the top, I ripped out the OE Lucas fuseblocks and replaced them early on in my relationship with my '66 1800, with a "gut D'german Qualitätsprodukt".  If you are interested in doing a similar upgrade to a multi euro-fuse arrangement where each fuse protects at maximum a couple of loads (instead of ONE fuse supplying ALL Battery powered loads, and ONE fuse supplying all Ignition powered loads, procure a 140 style fuseblock, and click here for a scan of my messy notes, made while I did the rewiring. 

My '66 1800S has sported a 140 fuseblock since about 1980, and has never had an "Inexplicable Lucas Incident".  It's close quarters on and especially behind the panel, but there is adequate room.  Visible at right is the "isolated stud" required by alternator upgrade.  Naturally, fuses and terminals are treated with Anti-Corrosive Zinc Paste.


External material sources are attributed.  Otherwise, this article is Copyright © 2002-2021.  Ronald Kwas.   The terms Volvo, Bosch and Lucas 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, 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, 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 unique metaphor and probably (likely) wise-a** comment. 


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