Apologies …. I got crazy busy at work as soon as I posted and then had friends come to stay over the weekend …. I kept meaning to check it but just haven’t had a chance.
I left it unplugged and have tried again and it seems fine now which is really weird, I got 4 x 18650’s and put them all in at the same time and the fan cut in as it should.
I hadn’t put the battery in the wrong way and did try using magnets on the ends before I posted this thread.
Think I may oil the fan anyway as it’s always been noisy, is there any oil I should use … is 3 in 1 OK or silicon spray any better
I’ll also look at the fan upgrade that’s been mentioned although I just want to make sure the unit’s OK before I spend the money on that and find the issue I had was the start of it breaking down and don’t see what else I can do but keep using it for now and see if the error occurs again.