Thursday, 25 November 2021

MGB demister demystification


For some reason the demister on this MGB never worked very well. To be honest, when I investigated the cause of this malfunction I found there was a good reason why: part of the system was missing and the air ducts to the demisters were not properly connected to the airbox so it could not have worked well for all those years I've owned the car.  

This was very hard to see and I needed to crawl into the tight space in the footwell.  Here you can see the rather tight work area, but with a torch I could just see how the plastic hose was just randomly inserted into the airbox. Some air might have been able to reach the windscreen, but messing around with the radio and electric connections had displaced the loose hoses, so now there was no airflow at all. I never wondered much about this, as it is an old car and demisting was accomplished by wiping the screen with a rag and driving with the window and quarterlights open anyway. It occurred to me this was probably not the way the car was designed, so I decided to investigate.  
Having found the flaw I cut two short ends of pipe and inserted these between the plastic and the two corresponding holes in the airbox. 
Here you can see the flexible hose refitted. You will understand I could not photograph the actual connection as I was working mostly by feel. It sounds easy, but I found it an uncomfortable task I'd rather have delegated to some contortionist.
Having a working demister, I decided I would like a better temperature gauge too( the old one is always reading low), so I fitted an old one I had scrounged from a scrap-Mini years ago. Much better. Now where do I keep a good fuel gauge?