Looking at 1699 recently I noticed a splashguard/cooling vent underneath the rectifiers on the body o/s. This is something I had never seen before. Was this something that was later deleted or is it something that has been added later to this bus?

If it's just below the body just behind the drivers cab more or less below where the first passenger seats are then this is original location for the original rectitier which would then run a feed up to the cab box.
Long obsolete but quite a few earlier buses retained the housing which usually rusts.

Thanks Jack,

That is what I was referring to. I have seen a number of buses with intact rectifier boxes, some with the guts still inside and some with the system still in operation, however this was the first with the shield underneath.

Apparently the original rectifiers were know as "toasters" for some reason...

I've come across 2 abroad in the last few weeks still with working rectifiers, 428 in Diepenbeek Belgium and 46 in Alsmeer Holland. The other one was with All-4-Event in Germany, but that burnt out in November so I changed the alternator and fitted a modern fag packet charging unit!

During my time on LT there were many RM`s that had this shield which could be readily seen as Jack says. Wasn`t the upgrade of this the subject of a revised code or derivative of an original one? Somewhere I have a list of what all those 5/RM/5/7 (or whatever) codes as carried on the brass plates above the bonnet were. It`s a long list - as there were so many - but whilst it lists the variations I`m not sure that it gives the reason and dates. I`m even less sure as to where I`ve put it and I doubt it`s readily to hand but no doubt someone else has one....

RM 238 still has this rectifier unit which is working. I expect it will have to be replaced with a new alternator and CAV 440D equivalent voltage regulator eventually.

My bus number (if any): RMs 238, 471. 2213 & GS1 7

Just supplied a replacement Simms rectifier for RM 1609, if this one goes then it will have to be as Chris says a new alternator and rectifier. It was called a toaster because that is exactly what it looks like.

There should be a photo here but it's not showing, It's on my Flickr site RTL960.

My bus number (if any): RTL 960, RMC 1458 RM 1585, (M 961, M 271 - both sold) and several RTs

It should be possible to replace the original rectifier with a set of diodes. I'm not that electrically-minded, but I know a man who is. This would save haivng to replace the 3 phase alternator.

Mind you, the more modern alternator with fag packet regulator does make life a lot simpler!

Yes you can replace the diodes Roy, but as a good one came to hand and the old one had already been stripped out, it was easier to replace it as a unit.

My bus number (if any): RTL 960, RMC 1458 RM 1585, (M 961, M 271 - both sold) and several RTs

I don't know if they are still in working order, but the Routemaster Association still has at least 6 in stock. They may possibly be useful for spares.

Don't forget that the Spares Open Day is coming up, so there is your chance to have a look at these then.

My bus number (if any): RM1368