We need them more than they need us. They go about their business charging our batteries until one day, usually at a quite inconvenient time they just stop - or worse, become inconsistent, sometimes charging and sometime not.
To my great shame I have not even got a spare belt on Percy, I know - I had problems with belts and alternators when we were out on Waterlily in June 2012. I think the breakdown we had that day put the seed of doubt in my mind about engines under deckboards with the result we had Percy (with an engine room) a year or less later. The problem then was a shorting wire under the alternator that was under or below the engine. Phil at Oxley Marine did a sterling job that day to find and repair the fault.
Anyhow the reason for the self reminder on belts and alternators it we got the charging light pop up on the dash on the car on Sunday just as we were about to set off on our weekly (for the last several months) trip back down south. Breakdown guy turned up - no meter, and said alternator is dead. 13 hours later including 4 hours at Leicester Forest East waiting for the second relay truck to relay us back south we were back in West Ashling. That was on top of 5 hours Friday afternoon/evening getting up... a pivotal weekend of crap journeys.
I live in a wonderful age of the internet where there is endless knowledge and some fine forums. The Rover 75 and MG owners forum is one such, masses of not just info but enthusiastic advice to get things repaired, not just thrown away.
So with all my virtual friends helping I went at the alternator in situ and took off the regulator and brush set. Now the real reason is this job is a pig on the car, a breeze on the boat (when ever I will do it) A bike ride to Screwfix for some deep small sockets and a tiny 1/4 inch drive ratchet, got the query defective stuff off. I think the brushes have just worn out after 130,000 miles ( its the original alternator) I could try a £1 fix, I had the new brushes in my hand at a little workshop that sells such stuff, but bottled it and decided to order the regulator and brush assembly. Fitting hopefully later to see if the diagnosis is correct....
So much easier on a boat that a car - in the main. A pic of the exposed slip rings waiting for their new brushes. They are worn but the consensus it they have many more miles in them.