I don't believe the pump will be worn out on a boat fridge. Think about the fridge/freezer that's been in aunty Mauds house for 20 years without stopping, although it's getting noisy... Morgana's right, If I remember the pump runs on AC at some odd frequency (400cps?) Anyway, sticking a battery across it won't help. The Waeco system doesn't self-seal, so if you take it to bits, you will need to send the whole lot back to get it recharged ( unless you can source a local engineer with the vac pump etc.) If you have a "mobitronic" power supply, the battery volts go though it to the compressor (via internal relay) and become 24v when you're on shorepower. You must, therefore, measure at the push on connectors on the controller to see what's really happening (with the fridge switched on and turned up). If it has a fan, does that start? ( or the pump if it's water-cooled). (different part of the controller)