Bloody sods law – I have a fridge freezer which is just about to turn three year old and recently has been switching on more often than previously. As it needed defrosted I pulled it out to wipe the dust off the compressor and other bits at the rear and now I have put it back in place the motor is running constant, the fridge is barely cold and the freezer is freezing water droplets but nowhere near -18. Any thoughts would be much appreciated thanks.

Sounds like it has lost its gas. Has it been moved recently? This could have knocked a pipe and caused it to leak.

I've had two Bosch fridge freezers both were shit, so much so the second one (which was a warranty for the first) the engineers stuck condemned / scrap stickers all over it when it died.

Yep I moved it to clean it and when doing this I noticed one of the pipes was corroded. Is it possible to regas or is it a case of it being scrapped – so much for paying extra for the supposed quality brand.

I've had two Bosch fridge freezers both were shit,

mine was carp too…doesn't really help the OP unless you need to buy another

mundie, you can regas. And if the pipe is easy to access to repair then it should be straight forward. Only thing to be aware of is how long has it been like this? If its been leeking for a while, then what happens is that the poor compressor slowly cooks itself over a number of days/weeks as it runs continuously to keep up. Only way to be sure is to regass it and see. My dad used to repair fridges and freezers and I carried his equipment from the age of 6, so I have seen plenty of broken fridges.

Cheers squire for that bit of info – it appears that the freezer is now working (it freezes but not down to -18) but the fridge is @ room temperature with the compressor going all the time. Could it be just the stat?

Maybe you've already tried this – switch it off for a few minutes to reset the magnetic coupling between motor/compressor, then switch back on.

Mundie. NO. The stat is a switch. If it sticks off then you hear no noise and your chips defrost and milk goes off.
If it sticks on then it runs all the time and your milk gets a bit frosty!

Also some fridge/freezers have two compressors. If you have this then you will have two thermostat controls. Each has its own gas circuit, so its perfectly possible for fridge to be knacked and freezer to be fine (or vice versa).
If you only have one stat then the fridge uses same circuit as freezer, so both would be knacked together. You can also tell what you have by looking at the back as you can see the compressor (big black lump with lots of pipes).

Simple things really these fridges.

It'll have lost its gas. Our Bosch did the same at about 3 years old. I put a squirt of gas in it a couple of times and it'd be ok for a week or so, just replaced it with a decent fridge/freezer in the end though. Wasn't worth the hassle of finding and repairing the leak. More used to working on big commercial and industrial stuff.

And if the pipe is easy to access to repair then it should be straight forward

For a fridge engineer. you'll need manifold gauges, a line tap valve, a vacuum pump, oxygen free nitrogen and refrigerant. Plus probably brazing kit. I reckon £100 worth of repair.
Adam is right, it's probably lost its gas. The weakest area on domestics is the capilliary tube (very small bore pipe). It acts as an expansion valve and leads into the evaporator (cooling coil on the inside). Even a cable can rub through these. You want to check that the evap is completely clear of ice before calling anyone in though.