Ah, there are different senders are there? In the wider world, yes. how would I find out the range of the one that Caterham has put into the sump tank already? The two best approaches might be: See what's worked for others (as you are doing). I haven't seen any suggested mismatches, but I haven't ploughed through all of the previous discussions eg in #2. Identify what you've got and check the specs. Have you got part numbers for the two senders that you want to connect?Jonathan