A.k.a. the PortaCount's 'check engine' light

TSI claims the 'service' message appears with low alcohol or moisture-laden wicks, high temperatures, and if none of those are true, with dirty 'internal lenses.' Seems sensible enough...

...but, we've already covered how to clean the 'internal lenses', and changing the alcohol cartridge is easy enough, so what really is causing the 'Service' message to appear? And for that matter, why does it appear when it's hot outside (as seen in the troubleshooting guide)?

As far as I can tell, with one well-used PortaCount that has had every possible thing changed about it not involving the laser, including, but not limited to, changing the filters, and of course, cleaning the sampling cone 'internal lenses', leaving only the laser itself. Which leads to a somewhat profound conclusion:

The 'Service' message appears when the PortaCount photodetector thinks the laser is off its calibration.

It would explain why moisture and hot temperatures, presumably especially in humid climates, would cause the 'Service' message to appear. But it also may appear when you've been using the PortaCount for too long, presumably due to laser drift as the hours on the laser diode increase. So... don't do that.

Some (somewhat obvious) Tips for Avoiding Excess Hours on the Laser

Assuming you've done all you can to eliminate other causes of the 'Service' message, if it actually is caused by the laser drifting, you will have to spend a arm and a leg trying to get it recalibrated by someone with the proper equipment, which around $800-$1000+. Ouch. Here's how to avoid that:

• If you ever need to do the drying procedure done in the PortaCount manual, which essentially involves putting the Zero Check filter on, and putting the PortaCount into 'Count' mode to stop it from turning off until 2-24 hours have elapsed, well, don't do that. Instead, leave the PortaCount off for a week, (with its cover on to protect the sampling cone), to allow the alcohol to evaporate without having to put hours on the laser counting nothing.

As far as I can tell, leaving the PortaCount off to dry for a week works just fine, even in my somewhat rainy climate, but your experience may vary.

• Leave the PortaCount off when you're not using it.

I'm assuming, unlike light bulbs, turning them on and off constantly isn't going to shorten a laser diode's lifespan, but again, your experience may vary.

And, in addition to laser manufacturers being mum about life expectancy details, no one really knows what sort of laser TSI uses, and no one really wants to open their PortaCount to check either, due to the relative rarity of PortaCounts themselves. I guess that leaves the last tip for this thread:

• Try and maximize your usage of your PortaCount each session.

It seems it's all we can do, really.