August 2009 (Addition)
Intermittent wipers are something which we take for granted in modern cars but it is not something which is standard on the old MGs (and thus not on NGs either). Fortunately Smartscreen do a range of electronic wiper controls (photo 1) which do not require an extra switch and can be fitted in a concealed position maintaining the vehicle's original look.
The principle of operation is that a repeat is 'programmed' using the standard wiper switch. The Smartscreen unit remembers the interval (anything between 3 and 30 seconds) between switching and repeats it. An additional feature of the unit I fitted (the SS05/P) is that the wipers are triggered for a few wipes whenever the electric washers are used.
I should point out here that the 'normal' unit with washers recommended for the MGB is the SS05/N as its washer switch is between the washer pump (which is connected to +12v) and earth. The Smartscreen is therefore triggered from the negative side of the pump - thus the 'N'. However, on the NG we normally connect the washer pump between the washer switch (which is connected to +12v) and earth. The Smartscreen is therefore triggered from the positive side of the pump - thus the 'P'. (My thanks to Smartscreen for explaining this to me). I understand that most MG suppliers stock the 'N' version so, if you want the 'P' version, I think it is best to order direct from Smartscreen as I did. There are also other units available though which do not have the wash/wipe facility.
The fitting is quite straightforward, the majority of the 6 connections being in the vicinity of the wiper switch. Image 2 shows the old and new wiring for the wipers & washers. For full wiring details see the downloadable PDF.
After testing, I simply cable tied the unit up behind the dashboard (photo 3) out of sight. The intermittent aspect works quite well once you are familiar with it and 3 automatic wipes are very useful after using the washers.
Click this icon for a PDF version of the Smartscreen Wiper Wiring which you are free to download.