My RM4230 fridge is coming to the end of its life and I am struggling to find a replacement. I believe its direct replacement was the RM5330 but this itself has now been discontinued. Has anyone found a wheel arch fridge that would directly replace this?

Failing this, I have found a similar (different model) Dometic fridge that looks in good condition. Are the coils/compressor exchangeable parts?

Thank you!

Dometic don't do a replacement for the RM4230 wheel arch model but Thetford are on the ball and their N4080 will fit.
It's slightly larger in depth so you'll need to check to see how much wiggle room is available in your van.

Thetford's tend to be much cheaper than Dometic's but they require a permanent 12V feed to power the electronics which the RM 4230 doesn't.

The cooling matrix on any absorption fridge isn't replaceable.

Be careful about fitting older 2nd hand gas appliances, particularly fridges - they've been replaced for a reason.