While getting ready to go into the water a few months ago I decided to remove my Suunto SK7 from it's housing and put it into a DSS gauge mount however in the process of removing it from it's old mount I twisted something wrong (oops) and began smelling kerosine ... not a good smell while standing on the beach in full gear. I soon realized the entire gauge had come "unglued" at it's seam. It has since sat upon a shelf waiting for me to fix it (I don't use a compass much around here as you can tell) After researching online I failed to come across anyone who had sucessfully repaired their compass, lots of folks complained of bubbles (some to the point where the compass no longer worked at depth) but the answer was always "throw it away and buy a new one." I did not like that answer, so down to the local plastic shop I went where they sold me a tube of #6 This is different from #3 in that the surfaces being mated do not have to be exactly flush - it fills in gaps. While this does not provide as clean a look when finished it was just what I needed.
As my compass had split right along the seam it was a simple job to reseal it. Be sure to allow 24 hrs for curing before filling. The difficult part came in how to fill the compass module once it was sealed. I wanted the "fill" hole to be as small as possible, so I could use the #6 cement to fill it with later, and not need an acrylic "patch". I took the tip of a thumb tack and heated it (using pliers, not fingers of course)
Once nice and hot I simply melted a small hole in the edge of the compass housing. I chose an edge that was going to be my high point for filling.
Refilling the compass module was the most time consuming part of this project. As I wanted to keep the fill hole as small as possible I used a tiny syringe bottle (actually made for apply cement #3) the needle is only 1/16" diameter, so it's quite small. I filled the compass with mineral oil and it turns out the bottle holds exactly the amount needed for filling the compass module.
The last bubble was the most difficult to get out, but once all bubles were gone I dried the area around the fill hole. Be careful not to squeeze the compass at all as you squeeze out some of the mineral oil and reintroduce an air bubble again. Once filled with mineral oil I then put a drop of the #6 cement over the fill hoe. This was the only time I had a problem. As the cement dripped into the fill hole it introduced a tiny air bubble (seen on the image below) but as the air bubble is so small I do not anticipate it creating a problem.
After the project was over, back into it's comfortable DSS gauge mount, and it now is simply waiting for the #6 cement to finish curing so I can test it in the water, but it looks like a sucessful project.
No guarantees this will work for you, but if you have been told "just throw it away" it may be worth trying to salvage your compass module.