Tusa SAV-7 shutting off at depth

[gsus1964]

I recently purchased this used SAV-7 and have 10 dives on it. Starts and runs fine on the boat down to appoximately 80'. It begins to run intermittently and or shuts down completely the deeper I go. No signs of water inside.. Battery is fully charged.
Thanks for any help in advance

 

[jamesb]

Clean the four knitting needle like pins in the motor case next to the battery and put light grease on them to prevent corrosion. Remove the aluminum cover on the board inside the upper case. There are eight little fingers that make the connection to the pins in the motor case. Make sure they are clean and gently realign them if one is twisted to the side. As you go deeper the upper and lower case squeeze closer together and the contacts move. That usually does it.
If it shuts off at depth does it restart as soon as you come up? There is a thermal breaker on the motor but that rarely pops.
Those contacts are very sensitive to corrosion and being loose.
I see many "fully charged" batteries that only last 5 minutes of runtime when they get old.

 

[gsus1964]

It does start as soon as I ascend... Will clean up the contacts and see what happens.
Thanks !