Repeated AL i470TC issues - advice?

[jetsettingbarista]

I need some advice on my i470TC.

I've had the computer for about 4 years, and it's in very good condition. However, on my last two dive trips, I experienced a weird error. After the first time, I assumed it was user error. However, when the error was reoccurred in the exact same conditions the following dive trip, I'm now fairly convinced it's my computer's error.

TL;DR: I went for a night dive in the Philippines. Standard 4 dive day, all well within a safe range. About 2-3 minutes after entry, I noticed my watch was incorrectly in gauge mode. Given that there was no gauge, the computer calculation assumed that we were at something like 300 feet (we were at ~15-20 feet the entire dive). Unsurprisingly, my computer locked me out when I came back to the surface without completing the recommended 12 hour deco stop.

After this happened the first time, I assumed that when I was updating the nitrox %, I fumbled the buttons and accidentally turned on gauge mode. Since that experience, I'm very careful when updating the nitrox and always return to the home screen so there was no chance of buttons getting bumped on accident.

However, most recently in Indonesia, the exact same error occurred. Oddly enough, it was in the same situation - a shallow night dive after several day dives. I was extremely careful about programming the nitrox and kept the computer on my wrist the entire time, so I am fully confident that there were no accidental bumps to trigger gauge mode.

I'm left concluding there is something flawed with my dive computer, but am stumped on what. Any thoughts? Any advice on dealing with AL?

 

[Belzelbub]

I went for a night dive in the Philippines. Standard 4 dive day, all well within a safe range. About 2-3 minutes after entry, I noticed my watch was incorrectly in gauge mode. Given that there was no gauge, the computer calculation assumed that we were at something like 300 feet (we were at ~15-20 feet the entire dive). Unsurprisingly, my computer locked me out when I came back to the surface without completing the recommended 12 hour deco stop.

I'm not sure I'm 100% understanding this correctly.
Was this the first dive of the day, or had you done another previously?
What do you mean by, "Given that there was no gauge, the computer calculation assumed we were at something like 300 feet..."? Are you stating that the computer was reading 300' when you were actually much shallower?

If the computer is in gauge mode during the dive, it will not give you any deco stops, so I'm unclear on the sequence of events. What I could see happening is that the depth sensor has gone bad and is reading much deeper than you actually are diving. On the dive that this happened on, the computer is calculating deco obligation, but you can't satisfy it. Once on the surface, assuming the DC now realizes pressure has dropped to surface pressure, it will lock to gauge mode for subsequent dives. And it will stay locked until the prescribed amount of time has passed.

Regardless, it sounds a lot like the depth sensor is toast. That's not a user serviceable item. You'll likely need to contact an Aqualung dealer/service center or Aqualung direct for service.

 

[TMurrr]

Buy a shearwater

 

[jetsettingbarista]

I'm not sure I'm 100% understanding this correctly.
Was this the first dive of the day, or had you done another previously?
What do you mean by, "Given that there was no gauge, the computer calculation assumed we were at something like 300 feet..."? Are you stating that the computer was reading 300' when you were actually much shallower?

If the computer is in gauge mode during the dive, it will not give you any deco stops, so I'm unclear on the sequence of events. What I could see happening is that the depth sensor has gone bad and is reading much deeper than you actually are diving. On the dive that this happened on, the computer is calculating deco obligation, but you can't satisfy it. Once on the surface, assuming the DC now realizes pressure has dropped to surface pressure, it will lock to gauge mode for subsequent dives. And it will stay locked until the prescribed amount of time has passed.

Regardless, it sounds a lot like the depth sensor is toast. That's not a user serviceable item. You'll likely need to contact an Aqualung dealer/service center or Aqualung direct for service.

Hey Brian - thanks for the questions. Tackling below.

Dives - both times, 3rd or 4th dive of the day. I don't believe it's relevant to the problem, but shared for context in case I'm wrong.

Mode - so I'm working on limited understanding on this, as I've never intended to use gauge mode. I'm not sure what mode is triggered erroneously; I only know on both dives it read I was at a depth of ~300 feet and then required deco stops. Based on my repeated reading of the instruction manual, that may or may not fit the gauge mode instructions. However, the violation shown and lock out period both fit the gauge mode description:

• Violation - the section "VIOLATION GAUGE MODE (VGM) DURING A DIVE" image --> is exactly what I saw in both error states
• Lock out period - "NOTE: Once a dive is conducted in Gauge mode, the i470TC shall operate with limited functions with-out any decompression or oxygen monitoring functions. A 24 hour surface interval shall be required for the unit to operate as a full function dive computer in Dive or Free mode." --> TRUE

I looked at Freediving mode, and the UI didn't match exactly, as I never saw "Free" on the UI.

What's odd re the depth sensor, is that it worked fine both before AND after both errors once the 24 hour lockup was completed. Which would imply there's a software or mode issue, perhaps?

I've already called and emailed AL twice, to no avail...

Thanks in advance, for any suggestions!

 

[Belzelbub]

Dives - both times, 3rd or 4th dive of the day. I don't believe it's relevant to the problem, but shared for context in case I'm wrong.

The reason why I was asking about this is that a previous dive may have triggered a violation which put you into gauge mode. It's common for this to be missed if you aren't familiar with how it's shown. If previous dive had you down to 300' it probably had a deco requirement. Skipping it would put it into gauge mode for 24 hours.

What's odd re the depth sensor, is that it worked fine both before AND after both errors once the 24 hour lockup was completed. Which would imply there's a software or mode issue, perhaps?

Yeah. That is odd. I'm not familiar with this computer, but did see a reference to DiverLog+ app. I used to use the non + version with my Oceanic computers. As I recall, there was a way to upgrade the firmware through the desktop version. You might try that first. Perhaps there was a bug in the firmware that was fixed.

Changing the mode accidentally should not cause the computer to read depth greater than it actually is.

I've already called and emailed AL twice, to no avail...

Yeah. That's unfortunate. Given their current financial situation, I expected this.

Buy a shearwater

While I'm sure this isn't what you want to hear, if a firmware update does not fix the issue and AL is not responding, this may be the best option. The transmitter that works with your AL will also work with the Shearwater. For one thing, Shearwater is not likely to ghost you should you have an issue down the road.

 

[johndiver999]

I would soak in freshwater for a day or two (maybe there is salt build up?) and then give it another few tries in shallow dives where a screw up is inconsequential.

Assuming the battery is good and the computer was not subject to some significant physical impact, then I suspect the depth sensor. When the depth sensor starts giving you erroneous readings, I think the computer is toast - how can you trust it again for a dive where the data matters? At the very least you should probably have a second redundant computer, if yours is at all questionable.