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Theoretically with the points closed ie earthed it should read 0v. But a very low reading is ok Are you absolutely sure the resistor you have fitted is correct? The coil looks new, have you run the Rover satisfactorily before with this coil? Just check it is not stamped 45244 because that version of 5C10 coil is rather anomalous in that the primary resistance is just one Ohm rather than the normal 5C10 that is about 2.8 Ohms. If so it is carrying nearly three times the usual current. Can you measure the resistance of the primary? Also can you measure the current flow through the circuit which should be no more than about 3A or so?

The only thing is long term it might be advisable to give the small choke some more support as there only a flexible wire each end. With heat & vibration it might wriggle its way out of the grasp of the grommet. Once you have tested it then perhaps replace with a stout piece of copper wire (18 SWG) between the resistor terminal to the start of the winding on the small choke. Although if you are not bothered about a small degradation in interference suppression you could dispense with the choke & have just a normal wire from the resistor to the first capacitor. Ok on the spider!

Yes fine. What is that bit of stuff in the corner close to the vertical choke?

SW on coil shouldn't go to the coil, it should go to the filter box. CB on the coil should go to distributor (as in Contact Breaker) With the points closed current will be drawn through the filter box (resistor) & the coil which is in series with it. So there will be a voltage drop across the resistor. Obviously earth the negative lead of the voltmeter & the positive on the output of the filter box ie the lead that feeds SW to the coil. Once the points open no current is drawn so the reading on your SW connection will be 24v not 10v or so. With the engine running if you have what I call a proper voltmeter rather than digital it will be about 18V ie averaging between 10V & 24V.

I've got some G932 if that is any good.

Yes, put a smear of heatsink compound on the base of the resistor before you mount it & it might be as well to smooth off the paint to bare metal to get best heat transfer on the area that the resistor will sit.

Stevan I assume you are referring to soldering in your new metal clad resistor, in which case 60/40 is fine. Just be wary of modern solder that has no lead & is difficult to make a decent joint. Make sure you make a good mechanical joint into resistor terminal before soldering. The silver soldering was the method of enhancing the connection of the original windings to their brass terminations & not needed for what you are doing.

I wonder if these sockets are wired in parallel? So either socket would power it up. The reason might be that this could be used in some other vehicle as well with different supply locations or it was a means to daisy-chain equipment so that it could provide an output for say a map reading light, the connectors look similar for that.

Do you know the original Army registration so you can trace its history?

Indeed it took whatever people could throw at it.

Ah different sort of Humber, this was the one I sold about 5 years ago.

The most common problem was water ingress because despite being in a sealed diecast box it was in close proximity to a removable windscreen which rarely formed a watertight seal. Fault finding often challenged people because even when the circuit breaker was open due to heating or more commonly corroded contacts a voltage could be detected through the energising coil. People understandably thought that with the circuit breaker open there would be no voltage detectable at the output. Particularly if they were using a digital voltmeter, but if you use a basic tool like a prod with a bulb you find that this voltage is of no use as it is in series with the circuit breaker winding & will not illuminate the bulb. This is one of those many instances where a top of the range fancy meter is of little use & at worst gives misleading results yet a crude bulb & probe with some common sense wins out : )

My only MV nowadays is this TUM(HS) ex 51 Sqn RAF Regt Airfield Defence now with a hard top seen here last year at the Dunchurch show. My Shorland after 33 years of ownership is now in Ulster Transport Museum.

Yes 8A is fine, it is not critical. It is only carrying about 3A.

5A I suppose would be best.

Yes in the white wire. In various applications I use blade fuses that can plug into crimp-on Lucar connectors. In all the Rovers I have had I never fitted a fuse in the ignition circuit. The Humbers I owned had ignition circuit protection in the form of an auto-reset thermal cut-out.

They sound useful, do they have a name?

I think glass fuses & their holders were seen as a potential weak link in early Land Rovers particularly as they were designed for working in an off-road environment. I think the view was that it might be preferable to continue with a smouldering ignition circuit than suddenly lose power in some critical situation. Bearing in mind the driver may not be electrically knowledgeable. It can be tiresome enough working your way through the four fuses you already have and ensuring there are replacement fuses to hand! I suppose for peace of mind you could fit an in-line fuse in an easy to access but secluded place. As the coil draws just over 3A then a 5A fuse would do it, but for a keep going but perhaps with a bit of smouldering fit maybe a 10A fuse. I think an important step is to fit an isolation switch in the earth lead of the battery, in a place that is quickly accessible. I remember once using this to kill the power when I saw the loom start to smoulder!

The tube repair is quite ingenious but the problem here is that the fine wires of the smaller resistance are quite close enough & can sag when hot. The increased diameter of a tube may increase the chance of shorting out especially as the crimped tube will in places be wider than the original tube. The other thing is that the resistor will be carrying at least 3A & anything other than a silver soldered join may give rise to corrosion and with all the heat, moisture & vibration is a far more hostile environment than being static in the controlled environment of a telephone exchange where perhaps quite low current circuits are in use. But a good idea I had not come across before.

Robin the connectors are entirely different for the generators & their panels. The original 2-speed 25A dynamo was Generator No. 2 the replacement was the 90A alternator Generator No. 10. There is a Ferret wiring diagram for this towards the end of my All Charged Up article.

I've sent you a PM

Steven it definitely won't work if the ballast resistor is open circuit. The resistor winding tends to break at an end, had you thought of undoing the broken end & trying to clamp it to one of the bolts? I don't think the reduction in resistance would be a big issue. A thing to watch is that the central carbon brush in the distributor cap is present, not worn out & can freely move on the spring. The other issue you didn't mention is the condenser. Is it new or old, but even an unused old one could be defective by now. This is another area of misunderstanding, often an electronic expert is consulted who tests it on an Avo or other multimeter & pronounces that it is ok. This shows a lack of understanding by the expert as the condenser can only be tested at the working voltage which is about 300v not at a few volts from a multimeter. Although that might rule out a short circuit, but I have tested many hundreds of distributor condenser & never found any that would leak so badly as to be detected by a multimeter. As for the substitute replacement resistor I confess I have never run it for more than 30mins & it didn't get unduly hot, but this was a bench test at the time I no longer had a 24V Land Rover at the time. The ideal I suppose is the correct resistor, but I have never seen one for sale in recent years. Although I have found these I had salted away. PM me if interested.

Steven glad you are on top of the polarity issue. You don't want a spark at the points! That is the sign of a defective condenser whose job is to absorb this 300V Back EMF & minimise the time for the magnetic field to collapse. Apart of course from minimising the arc wear on the points. But I am afraid Land Rover & classic car forums are awash with this nonsense that a good spark at the points is the sign of a healthy ignition. I have just given up trying to explain but moderators & the majority rule as they think a spark there is good. I have similar arguments about the value of wiring the coil primary correctly, often quoted at me is a nonsense classic car forum where it states that the coil "senses" the polarity & adjusts accordingly. Doesn't explain why coils were made specifically for positive or negative earth polarities. There are even sellers of quality made repro coils who haven't the faintest idea about earth polarity design & call them "universal" polarity. I despair at times so just let them get on with it!

Steve I can see where you mean but never seen a grey wire, it usually black so I wonder if someone before you has been poking around inside? I don't understand that you are getting any voltage if part of the resistor is open circuit. Although you say "I only had 5v at the low tension lead coming out of the coil," so you were measuring the voltage on the CB side of the coil & measuring it through the resistance of the primary winding of the coil? The place to see where your 10V should be is on the SW side of the coil where it emerges from the the filter box with the points closed. There may be an additional complication because a large number of coils even in service were fitted incorrectly. This is because the replacement coil comes with a clamp fitted 180 degrees from where it should be & to reinforce this error the polarity warning sticker is not in the best place by being on the top of the coil so mounted. There will be two rubber bungs on the coil cover, these should be pointed downwards with one bung removed to allow condensation to drain. If it is mounted so you can see the bungs or holes uppermost because of the length of the screened cables there is only one way to fit them & that will mean the CB & SW leads are interposed. Leads the wrong way round will mean you run with a positive spark rather than a negative one and have 600V less HT than if it was correctly wired. This could means poorer performance in terms of generally running & loss of power. As well as us talking at cross purposes about which lead is which! Some owners have noticed an improvement in performance after the correction, but a few others maintain that this was the way it was fitted in service so that must be correct & besides it runs ok. They seem to feel that my suggestion must some later idea. But this issue about incorrect mounting of these Lucas coils was highlighted in an EMER in 1957.

Steven the "old grey wire" is that from the ign switch to filter unit? It was originally white, 5A should be ok but the important thing is that the insulation is of reasonable thickness, so going to 10A might be better. Any internal wiring inside the box will be subject to quite a bit of heat from the engine & before the twin choke system wire was covered by a heat resistant sheath I knew as Systoflex. Over the years I have had many people concerned that the voltage out from the filter box is either still 24V or around 18V. When the CB points are open no current is drawn through the filter unit so the resistor will not drop the voltage & it will measure as 24V. Once the points close it will drop to 10V ish. With the engine running the output voltage will be swinging from 24V to 10V, but the needle of an analogue meter cannot move this fast so it is mechanically averaged between 10V & 24V = 18V ish. I hate digital meters for automotive diagnostics. The display jumps around & I have to do a mental digital to analogue conversion which is tedious when I just want a ballpark reading or to see a trend of voltage change. A digital meter so often can read gibberish voltages when it is not even connected to anything, this is even with a top of the range military grade Fluke. I use an Avo 12 it is an old fashioned, hairy-arsed, no nonsense, low ohms per volt, quality British, reliable meter specifically for automotive electrics & marked inside is the REME workshop number, which is good enough for me.