30-04-2020, 08:38 PM
Hi David H
Allowing for the vagaries of your multimeter, those figures look mostly OK.
However, the resistance from +D to A with points closed should be VERY low, (a fraction of an ohm ) as it is just the resistance of the closed points plus the thick "current" (series) coil. This sort of resistance is hard to measure accurately with a normal multimeter. One check is to short together the probe tips of your meter (push hard for a good contact) and see what it reads. If you don't get almost the same reading when you try it on the cutout, that would raise suspicion.
I find that when measuring the generally low resistances of car circuits it is often necessary to use sharp meter probe tips and to really push hard/scrape/wriggle to get a good enough contact, as the metal surfaces build up a film of poorly-conductive oxide. Measuring voltage is less critical, as the meter's own resistance is so high that a bit of extra probe resistance doesn't affect the reading nearly so much.
Happy trimming !
Allowing for the vagaries of your multimeter, those figures look mostly OK.
However, the resistance from +D to A with points closed should be VERY low, (a fraction of an ohm ) as it is just the resistance of the closed points plus the thick "current" (series) coil. This sort of resistance is hard to measure accurately with a normal multimeter. One check is to short together the probe tips of your meter (push hard for a good contact) and see what it reads. If you don't get almost the same reading when you try it on the cutout, that would raise suspicion.
I find that when measuring the generally low resistances of car circuits it is often necessary to use sharp meter probe tips and to really push hard/scrape/wriggle to get a good enough contact, as the metal surfaces build up a film of poorly-conductive oxide. Measuring voltage is less critical, as the meter's own resistance is so high that a bit of extra probe resistance doesn't affect the reading nearly so much.
Happy trimming !