Dwell hasn't been needed since points went away and wasn't really needed then-could set more easily with feeler strip.Points started to disappear about 1975-replaced by Hall effect in the distributors of that day-then distributors went as well!Since then I've used a Fluke 88(paid for by my employer)-I couldn't afford it tho' it was very good-for my own personal use,I found the cheapest one I could buy(less than £10) served the purposes I needed it for ie. to give an indication rather than extreme accuracy.I had a timing light with a tacho built in.

I don't agree with that at all. Checking dwell angle is just as useful on a modern car as much as it was on one with a simple points and condenser ignition system. The fact is an electronic ignition system works in exactly the same way. The only difference is the coil is switched on and off by a transistor (an electronic switch) rather than the points (a mechanical switch). Also the dwell is variable on electronic systems where on a points system it's constant. So that actually gives more reason to use a dwell meter, to see if the dwell angle increases with engine speed.

The dwell angle is the number of rotational degrees during which the ignition coil is switched on. Eg, there are 360° in a circle, so a four cylinder engine is 360 ÷ 4 = 90. Of those 90° the coil will be switched on and off once. So if the dwell angle was 50° the coil would be switched on for 50° and off for 40°. As I said earlier points systems are constant dwell, which means this ratio will not change. This is the exact opposite of ideal though because the faster the engine runs the more coil switched on time we want to allow the magnetic field to build up. So electronic systems are variable dwell so the coil stays switched on for longer for high engine speeds and less time for lower speeds. This means the HT spark does not begin to break down or weaken at higher speeds. Electronic ignition system coils have lower primary winding resistance than a conventional 12v standard ignition coil. These are not interchangeable. Fitting a coil with the wrong primary resistance will cause problems.

Car is 1986. Don't think my points have disappeared yet, though the current set is a bit worn, so I suppose they've "started to disappear". I do have a couple of spare sets though.

I have a timing light, and much to my surprise, actually found it in Taiwan ((!). The old geezer who dug it out of the stockroom for me was quite misty-eyed with nostalgia, or maybe just allergic to dust. No tach although the dash has a rev counter

I bought a cheapo multimeter first but it soon became a cheapo random number generator so I got a fairly good one next time around. This has lasted almost a decade, . Took it apart this afternoon and cleaned contacts with cotton buds and contact cleaner, but no revival.

EDIT: I do have a rectangular strip of plastic left over about the case width long and half a cm deep with two smooth circles at the ends, which evidently fell out of the case unnoticed. Dunno what it does or where it goes, but I suppose I'll have to try and put it back. Probably wont make any difference though.

Over a few days prior to failure it took gradually longer to "wake up" the display after switch-on, which I suppose might be diagnostic if I knew how to interpret it.

Might just get another one if I can't find a reasonable automotive meter

Edited by edlithgow on 04/01/2021 at 00:17