Pro9000: Low ink warning not working for some colors.

I purchased recently a secondhand Pro9000 in great shape, including the printhead. Not a single nozzle missing in the extended test.
After being working some weeks with no issues, yesterday I noticed an almost sudden disappearance of yellow color in the prints. As the ink status for yellow showed full, I feared flow problems but when I removed the cartridge it was totally empty. Even the sponge, specially the upper part, was quite discolored meaning that it has been sucked dry. Apart from the printer status showing 'full', the led on the cartridge itself was steady red. No flashing at all.
Smelling a rat, I checked visually all the other colors. G,C,M,PB,PC and PM showed less than full in the driver status and all had still a noticeable amount of liquid inside, so it seems they're fine, but the red cart was like the yellow : totally depleted while the status in the driver was 'full' and the led in the cart was lighting steadily.
So I have now two colors -Red and Yellow- where apparently the ink status is not working anymore. I wonder where can be the fault. The chips, the printhead, the printer ?. Of course, if the new Yellow and Red carts work normally the fault must be in the chips of the older units but if they behave like the other two, then the problem must be in the printer or the printhead. For the record, these troublesome carts are original Canon and have been refilled/resetted several times ( the chips are also original).
Any clues, folks ? .. It's not rare that a chip fails, but then the driver and the led of the carts warns of a faulty condition. My issue seems to be the other way around.

Did the ink leak out? If you use the top fill method and there is not a perfect seal of the refill hole then out goes the ink. Look for residual ink in the print head or in the printer itself. Leaked ink may also contaminate nearby cartridges.

Chip failure is possible, though it usually is one that will not reset or be recognized by the printer. This particular scenario, while not the one you describe, could also be caused by a low battery or failing chip resetter. Having two failing at the same time in the same fashion is unusual. Too soon to tell what the reason is.

It may be time to get a fresh cartridge for the "malfunctioning" ones if the issue was not a leak.

I tend to agree, its more likely to be a refill problem due to leaking cartridges, two chips going wrong at the same time is highly unlikely...

Thanks for the hints folks but I don't think this is a case of ink leak at all,
Before inserting a refilled cartridge in the printhead slot, I check for any leak holding it a few seconds over paper towels. Sometimes one or two drops drip, if I've overfilled, but that's it. Massive ink leaks make a mess, with cross contamination and terribly smudged prints. I've had a few of those "events" in the past (as many of you, I expect). In this case, prints and nozzle checks were perfect until yellow cart was totally starved. After replacing the "culprit" carts with newer ones, everything went back to normal at once, so no burnt nozzles luckily.
Thinking twice, I realize now that with the number of prints I've done lately, the fact that yellow ink status was still totally full while cyan, magenta and the others were declared empty by the driver and had to be replaced at least once, should have raised a flag in my mind. Been a bit careless, I reckon.
Anyway, even if it has been some ink leak (I'm pretty sure this isn't so ) the optical detector wasn't triggered either when the liquid chamber reached empty. This is very puzzling.

I would still replace the two carts that emptied un-expectantly or at least change the chips, you don’t want the same thing to happen again, but if it does then you’ll know what caused it...

I might have found the problem. I replaced the current black cart with an empty one which hadn’t been resetted. and the status for black ink showed empty as it should. Then I resetted that cartridge but I didn’t refill it and the printer recognized it as full, even if there wasn’t a single drop of ink in the liquid chamber. Same thing happened with an empty green cart. It seems then that this isn’t related to individual colors but rather that the optical detector isn’t working at all.

This is a secondhand printer so I don’t know if the original owner was already aware of the issue or not but, after two months, I can’t ask now for a refund or anything. Anyway, it wouldn’t be worthwhile cost wise.

Artur5 said:

I might have found the problem.

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There is nothing wrong with your new printer, its behaving exactly as it should, the prism, optical sensor and chips are a complete package which are finely balanced to work together and give 100% accuracy and reliability, BUT.

If at any time you interfere with this setup it stops working, and in this case, you did by resetting the chip without refilling the cart, this causes the ink monitoring to be disabled by the printer !

By resetting the chip and not refilling, your printer is not fooled by this action at all, but instead it’s you that’s been hoodwinked by the printer, it won’t respond to any information from the prism, optical sensor or chip, nor will it relate any of this information back to you. (Speed on brother hell ain’t half full)

You were lucky this time and spotted the problem before you lost your print head, by interfering with the ink/chip setup you are voiding any responcipaliby by Canon to protect the print head from damage, the golden rule on a low ink warning is, reset, refill, reuse, and your printer will be very happy...

P.S. When one carts gets low, replace any other carts that are showing near or below half full also...

Glad you figured out the reason.

It may be the optical sensor does not kick in immediately. You did not say how long your tried printing with no ink. One way to test is to reset and refill the suspect cartridges and continue using them as usual, but keep an eye on them for when the ink is low to none in the reservoir side. Then monitor closely for a a print or two to see if the optical sensor kicks in at some point.

You could facilitate this experiment by resetting the chip and refilling with ink to just a small amount in the reservoir side, just enough to make sure ink is being used up by the cartridge during printing.

The Hat said:

By resetting the chip and not refilling, your printer is not fooled by this action at all, but instead it’s you that’s been hoodwinked by the printer, it won’t respond to any information from the prism, optical sensor or chip, nor will it relate any of this information back to you.

Click to expand...

I've been under the impression that the optical sensor provided a fail safe mechanism to warn of unexpected low ink. No extra coding required, just reporting when no ink remains in the reservoir side whether in the normal course of using the cartridge or in the advent of a catastrophic leak.

stratman said:

I've been under the impression that the optical sensor provided a fail safe mechanism to warn of unexpected low ink. No extra coding required, just reporting when no ink remains in the reservoir side whether in the normal course of using the cartridge or in the advent of a catastrophic leak.

Click to expand...

All of the above are correct, but that is under NORMAL circumstances, and not when you start with an empty reservoir and a chip reset to full, because these conditions are not NORMAL, therefore the printer will not protect you, under these usual situations print head suicide is legitimate...