109ffr Posted March 3 Share Posted March 3 Good afternoon all. I have a series 3 109 ffr landrover with a failed ballast resistor in the 24 to 10v stepdown box for the ignition. Having read Clive Elliott’s article on the 24v system, I see he has the wirewound aluminium clad 50w 5r6 resistor as a substitute for the original. I wondered if anyone has had experience with this, and if it is a success. Many thanks, Steven. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 8 Author Share Posted March 8 Clive, could I just ask, will it be sufficient to use 5 amp wire to replace the old grey wire to the resistor? The choke side seems in good condition. Also what voltage would be reasonable to expect on the low tension wire to the distributor if everything is working as it should? Thankyou, Steven. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 8 Share Posted March 8 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. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 8 Author Share Posted March 8 Morning Clive. Yes, it’s the section of wire on the capacitor to the resistor that is like an extension from the white ignition wire, the opposite side of the resistor to the black choke. With the engine turning over, I only had 5v at the low tension lead coming out of the coil, but that was with the digital meter. This was with the original resisistor with a large break in the small winding. In your opinion, would this cause a cranking but no start symptom? The car did die a couple of times in the week before refusing to start full stop. Thankyou again, Steven. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 8 Author Share Posted March 8 I will try and post a photo tonight Clive, if I can work out how to do it. Technology and me aren’t a good match. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 8 Share Posted March 8 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. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 8 Author Share Posted March 8 To be fair Clive, the vehicle did have the coil wrongly connected by the previous owner for many years, when I fitted the new correct coil the other day, this was rectified, and I’m guilty of the runs ok mindset and only swapped the coil as I had one boxed and ready on the workshop shelf in case it ever went. I have also removed one bung. It does sound as though that wire isn’t the correct one then. So if I go up to 10amp with a new section of wire from the capacitor to the new resistor, fit it as you recommend in your article, and test at the correct place, and see what I’ve got. Due to there being no spark at the points or the plugs, I was just looking for any voltage where I could find some. Panic mode I suppose. One the plus side, there was 24v going into the box. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 8 Share Posted March 8 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! Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 8 Author Share Posted March 8 Again Clive, Im guilty, I was looking to the points for a sign of life. It’s just nice to talk to someone who actually knows what’s what. As you say, there’s so much manure spouted that someone like myself just ends up confused. I’m ok with the mechanical side of things, but electrics are like black magic to me. The coil, I now know is done, the points are also brand new, and I have a new cap and rotor arm. I’ve got my fingers crossed that the break in the resistor is the cause of the problem. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 8 Author Share Posted March 8 Did you see any problems with the new resistor Clive, heat wise or otherwise with it being a lot smaller than the original physically? Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 8 Share Posted March 8 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. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 8 Author Share Posted March 8 The winding has broken, just my luck, about a third of the way along, right in the middle of the board! 🙄 The condenser is brand new, but by all accounts that doesn’t mean it’s ok, and I have a new cap and rotor arm. Sorry to sound thick Clive, but do I go onto the small envelope under fv1609 to message you? I’d be very interested. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 8 Share Posted March 8 I've sent you a PM Quote Link to comment Share on other sites More sharing options...
Citroman Posted March 8 Share Posted March 8 This type of windings can be repaired by stucking the ends in very small silver tubes and pinch them. It's the kind of connectors that they used in telephone connections in the past. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 8 Author Share Posted March 8 Those tubes must be tiny, and a very skilled repair I’d imagine. These days it’s all about throwing things away and buying a new one. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 8 Share Posted March 8 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. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 9 Author Share Posted March 9 Would an in-line fuse at a strategic point be a good idea while I’m at it. Fuses do seem to be an endangered species on the truck in general. Although not to tempt fate, has never been a problem up to yet. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 9 Share Posted March 9 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! Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 9 Author Share Posted March 9 Would a fuse on the white wire from the ignition afford an protection Clive? And now you’ve scared me, I’ll fit an isolator switch too! Quote Link to comment Share on other sites More sharing options...
Citroman Posted March 9 Share Posted March 9 I used the tubes on a repair of a toaster they get red hot every time, works well till now 😉 Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 9 Share Posted March 9 They sound useful, do they have a name? Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 9 Share Posted March 9 48 minutes ago, 109ffr said: Would a fuse on the white wire from the ignition afford an protection Clive? And now you’ve scared me, I’ll fit an isolator switch too! 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. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 9 Author Share Posted March 9 Brilliant job with the toaster Citroman! And thanks Clive, I’ll fuse the white ignition wire then. Would you stick to the 5 or 10amp fuse for that too? Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 9 Share Posted March 9 5A I suppose would be best. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 9 Author Share Posted March 9 Hi Clive, sorry to be a pain. The job on the filter box is coming along nicely, but non of the factors around us have any 10amp wire. I have 8 and 15amp, would either of these be sufficient for inside the filter box? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.