What are the external dimensions of the Suunto D4, Suunto D6 and Suunto D9 diving computers?

The D9 measures 50mm x 17.6mm
The D6 measures 50mm x 16mm
The D4 measures 50mm x 16mm

How can I adjust the contrast of the LCD display?

Unfortunately it is not possible to adjust the display contrast on these models.

Is the battery user replaceable?

No, it is recommended to have the battery changed at a Suunto authorised service center.

How can I find out how to perform basic actions such as changing a strap, pairing my transmitter, or cleaning the display?

Click here to view a full range of product usage videos

When examining the details of a dive with SDM the information shows that the dive computer changed from displaying 5 minutes ascent time (decompression required) to 4 minutes of no stop dive time remaining within a 20 second period. This was with very little change in depth. Please explain how this can be correct? 

This is quite normal, as the tissue pressures of all 9 compartment in the model are not updated at the same time. Also note that Asc Time includes safety stop time which may be 3-5min or even more. Please also keep in mind that the SDM software only represents a recreation of the data shown during the dive, and does not 100% correspond to the data displayed during the dive.

Can I switch modes between dives i.e. make two dives using air, third dive using EAN (Nitrox) , can the computer deal with this? 

It is possible to switch from Air to Nitrox mode but not the other way around until the no-fly time has counted down. The reason you cannot switch back and forth is that there is no CNS/OTU display in Air mode, although there is CNS/OTU uptake. If you could switch back and forth freely it would be possible go near the limits in Nitrox mode, and exceed them in Air mode withouth getting a warning.

In my computer current units are set to Celsius and meters. I want to change them to Fahrenheit and feet, how can I do it? 

To change from Celsius and meters to feet and Fahrenheit in the Vyper, Cobra, Vytec, Vytec DS and Gekko please proceed as follows: Press mode and scroll to Set. Press mode again and scroll to set preferences. Select and scroll to Units. Here you can choose between metric and imperial units. Confirm your choice with the Mode button. Please note that the older Vyper model (green or black) does not have user selectable units.
To change units in the Vyper2, Vyper Air, Cobra2, Cobra3, Hel02, D4, D6 and D9 enter the menu by pressing the 'DOWN' button for 3 seconds then select 'UNITS' from the menu.

Why are some of my dives no longer accessable or downloadable to the Dive Manager software?

Suunto diving computers have a circular memory, meaning that once the memory is full the oldest dives will be overwritten. The amount of dives you can store in the diving computer depends on which sample rate (the frequency at which data is stored) you have chosen.

Why can't I access AIR or NITROX modes on my diving computer?

If you dive with the computer in GAUGE mode then there is a 48 hour no-fly period during which AIR and NITROX modes are unavailable. They can be selected again once the no-fly time has counted down.