Problem with Nauticam D850 vacuum circuit

In the last couple of weeks, I have taken my Nauticam D850 housing out for about 4 dives and had an issue with the vacuum/leak detector circuit each time. The housing was bought new in 2019 and probably has 500+ dives on it. No problems with the vacuum circuit until now, just the usual battery changes.

What I am seeing now is this:

• Turn on the circuit, seal the housing.
• Pull a vacuum and the indicator light turns green.
• Hours pass. Maybe I dive, maybe not.
• At some point later I find that the indicator light changes from green to flashing blue (this indicates standby mode)
• The housing is still in vacuum, I can't open the back.
• I release the vacuum, and the light continues to flash blue.

I just changed to a new battery when I first noticed something fishy a couple of weeks ago.

The flashing blue is just standby mode, as if you turned on the circuit and did not pull a vacuum. It is not supposed to return to standby after you have pulled a vacuum.

It seems to me the circuit is malfunctioning big time. Anyone had one do something like this?

I had a D810 housing do that after 3-4 years, intermittently.  I don't remember what I did, if anything, to fix it, but I think it only happened for a week or two.  I put in a fresh battery and added a few more pumps to the vacuum and that may have helped.  I notice on my Z9 case that I had to pull a bit more vacuum than minimum or the leak detector goes off below about 120 feet, then disappears above that.

As you said it is going back to standby mode as it would when you just power the circuit on.  It is like it is re-booting.  A couple things might do this. 

If it drops power briefly for some reason maybe the power switch is a bit dodgy or a poor battery connection.   The circuit probably looks at reduction in pressure from the starting pressure so could well go to blue if power is lost and restored,

The other thing to check, assuming your housing has it is to check the blue reset button which could possibly be stiff/sticky.  This is the one you see when you pull off the front port.  If the rod that connects this button to the electronic package is stiff or stuck for some reason it maybe holding pressure on the reset button which eventually triggers a reset.  

Apart from that I can't think of anything else that might cause it and be potentially fixable.

5 hours ago, ChrisRoss said:

As you said it is going back to standby mode as it would when you just power the circuit on.  It is like it is re-booting.  A couple things might do this. 

If it drops power briefly for some reason maybe the power switch is a bit dodgy or a poor battery connection.   The circuit probably looks at reduction in pressure from the starting pressure so could well go to blue if power is lost and restored,

The other thing to check, assuming your housing has it is to check the blue reset button which could possibly be stiff/sticky.  This is the one you see when you pull off the front port.  If the rod that connects this button to the electronic package is stiff or stuck for some reason it maybe holding pressure on the reset button which eventually triggers a reset.  

Apart from that I can't think of anything else that might cause it and be potentially fixable.

I think that sound plausible. I will take a close look at the reset button assembly and probably clean/reassemble that as much as possible. I'll also take a magnified look at the battery contacts and solder points on the circuit board.

I looked at everything more closely, and honestly it looks perfect. I don't see any loose wires, corrosion, or sticky parts. 

I suspect I will need to send it for service and get the circuit replaced.