Just to check with all the discussion of meters, I pulled out a Elenco freq. meter (nice for inductance and freq, but I mostly use the Fluke - I like auto-ranging) and a pair of old RS analog meters. All read the same (after adjusting the RS' zero points) AND two unused 2.4 Ohm carts FROM THE SAME BOX reads 2.2 Ohms (on everything). These carts don't work - the "recovered" 4 Ohm, reads exactly 4.0 on the Fluke and 4.01 on the Elenco, so I am pretty sure there are no measurement errors here. It is possible that some wire has "thinned" somewhere (I see one dead 4 Ohm is actually 18k!), but how to explain the 3.7 Ohm reading on a 2.4 cart? A partially shorted bulk heater doesn't seem likely and the furnance "looks" good. And two at 5.7 with no glow, but get warm - same measurement on both makes me more sure it is correct.I've only ever torn down 1.5, 2.4 and 4 Ohm carts. The heaters were of equal value. IIRC G confirmed this across the product line. I'm not sure I followed your logic, but I just measured them.
It sounds to me like in at least one case you have two good heaters (one of which you see) that's being misread due to contact or lead resistance (or other instrument related failure)? In the other two cases, one heater is out? I wouldn't count on seeing the glow in a used cart, that can disappear in a few dozen hits as deposits start to build up. Take a peek down the pipe on a working one, I think you'll agree.
Exactly right, which is why I think the heaters are matched in power, since the hotter vaporizer eats more oil, the feed heater has to heat more. It's just a rough scaling but I think that's the logic.
OF
Also, I don't expect to see any glow after I load a cart. Before "learning" better, if I saw the glow on a 4 Ohm I would top it off - Now I know it means I held the button much too long (and I'm probably close to the "puff of smoke" that comes when 4 or 5 Ohm carts die).
-NDA