Laserjet 4+ low toner warning

[Ron Bean]

How does a Laserjet 4+ determine when it's low on toner?

I've been getting frequent low-toner warnings, with a "new"
(recycled) toner cartridge. This has been going on for a while,
and it still prints OK, which leads me to think that maybe it's
not really low (aside from the fact that it's only printed about
1500 pages).

 

[Bob Eager]

How does a Laserjet 4+ determine when it's low on toner?

I've been getting frequent low-toner warnings, with a "new"
(recycled) toner cartridge. This has been going on for a while,
and it still prints OK, which leads me to think that maybe it's
not really low (aside from the fact that it's only printed about
1500 pages).

There's a wire that pokes down into the toner heap, that measures
conductivity or something.

They do tend to go on for ages after the warning, particularly if you
redistribute the toner (take cartridge out, rorate gently about 45
degrees in each direction about the longitudinal axis).

If it's a remanufactured cartridge, the sensor may be faulty. Just keep
going until you get patchy printout. On average I get 4500-6000 pages
from a genuine HP cartridge.