fv1609 Posted March 11 Share Posted March 11 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! Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 I’ll sort that then. I’ve had to remove two of the legs that hold the top to the bottom of the box because they touch the resistor terminals. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 24.5v with closed points on the end of the Sw lead Clive. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 Only 0.14v at the points Clive with them closed and everything connected up. Resistor got fairly hot within less than a minute. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 11 Share Posted March 11 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? Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 Hi Clive, the resistor is a wirewound aluminium clad hs50w5r6f. I’ve attached a photo of the label from the coil, and the coil stamping matches the label. The coil is brand new, and the car hasn’t been started with it on. I swapped it in case the coil was the problem. I’ve only got one of the Hilka digital multimeters Clive. I’m on a big learning curve here, so will need to do a bit of reading on how to take the measurements you’ve asked about. The fun continues! Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 The resistance of the primary is showing at 2.5 Clive. I had to use two lengths of 8amp wire to reach the terminals, which showed 1.3 when I put the wires together, I subtracted the 1.3 to get 2.5. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 11 Share Posted March 11 That sounds spot on. It is awkward to reach into those deep set connections. I have some old leads I screw in, but you have worked around & you have got round the problem & eliminated the resistance of the measuring leads which often people forget about. Earlier you said you were getting 24.5V on the SW terminal with the points closed. But from the photo the SW lead is disconnected. It must be screwed into the coil to complete the circuit to draw current to get a voltage drop. The way to measure this voltage is from inside the filter box. I did most of these experiments 10+ years ago but thinking about the resistor should get quite hot. But it has a dissipation of 50W so should be ok. Bearing in mind a 12V kettle is about 100W although with the engine running the duty cycle will be less. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 Right, I measured the voltage on the disconnected end of the SW lead as per the picture, with closed points at 24.5v. That was obviously mistake number one. Then with everything connected up, points closed, I measured 0.14V at the points, which was when the resistor heated up. That was obviously mistake number two. But from what you’ve said, the readings so far would be what you’d expect from my cockeyed way of doing them? So.... do I need to have everything connected up as it should be, points closed, ignition on and test inside the filter box? If so, where is the test point I need to test? Thankyou for your help! Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 11 Share Posted March 11 The 0.14V reading suggests that if you are drawing say 3A then the resistance of the point you are measuring from to earth is about 0.04 Ohms which isn't important. The important things is that it is not reading 24V as that would indicate the points were not closing. But we know they are closing because of the heat being produced by the resistor. But for peace of mind you need to know the voltage from the output of the filter box. I agree you cannot access this via the coil this can only be done from the filter box either with it upturned & not screwed in, or for these test purposes solder a flying lead that for safety reasons you keep the insulation intact & just use the prod of your voltmeter to touch the inner copper. This is to help avoid this test lead touching earth. Once you have got this reading remove the test lead. You are only seeking the closed points reading without the engine running, the reading when running is not of great importance & anyway will be gibberish with a digital meter. In all off this don't get hung up about a good earth to chassis of the filter box or coil this has no bearing on the functionality of the ignition system. It is only important for radio suppression. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 I’ll go with the top off the box option Clive. If I understand correctly then, I test the coil lead SW inside the box with the red probe, and the black probe onto the nearest lump of metal, with the points closed, and the ignition on? Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 11 Share Posted March 11 Yes But don't leave it on & not running for more than a minute or so. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 Is that why my dad would never let us have the ignition on to listen to the car radio when I was a kid then? He always said it’d burn the ignition out. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 11 Share Posted March 11 Yes, a flat battery or the ignition coil overheats & explodes. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 11 Author Share Posted March 11 Neither is a good choice! Thanks again for your help, and I’ll update when I’ve tested the filter box output! Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 11 Share Posted March 11 You don't want this to happen. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 12 Share Posted March 12 As Marvin Gaye sang "There ain't nothing like the real thing" Could be the answer to your prayers & very cheap considering the scarcity. Never seen NOS ones for sale before. https://www.lmslichfieldltd.com/epages/BT4011.sf/en_GB/?ObjectPath=/Shops/BT4011/Products/"electrical store 93B" Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 12 Author Share Posted March 12 Brilliant Clive! Thankyou so much! I’ll get it bought! Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 14 Author Share Posted March 14 The filter box re-wired with the old resistor fitted. The new resistor has arrived. Shame to take it out of the packet really. Quote Link to comment Share on other sites More sharing options...
Mk3iain Posted March 14 Share Posted March 14 So nice to find things that seem impossible and then sadly rip open the package. I wonder if it is possible to find the correct wire and rewind these ? This thread has so far had 747 views, shows how interested folk are ! Keep it coming, we are out here and many are quietly learning with you as well. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 14 Share Posted March 14 Make sure that the windings are as parallel as possible. You can see how a slight sag as it heats up could short out a turn & repeat the original problem. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 14 Author Share Posted March 14 I really do have to thank people on the forum, and a very special thanks to Clive for all his help and locating a resistor. Opening a piece of history like that and using it really does feel wrong. In terms of re-winding the old resistor, my uncle knows a chap who makes pick-ups for guitars, and the chap says if he can find the correct gauge wire, it may be possible. As a spare, it would at least mean the filter box might have a bright future. Thankyou for your reply, it means a lot. Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 14 Author Share Posted March 14 I shall be very gentle doing that then Clive, it looks like performing brain surgery! Quote Link to comment Share on other sites More sharing options...
109ffr Posted March 14 Author Share Posted March 14 I think that’s as much as I can do Clive. Quote Link to comment Share on other sites More sharing options...
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