Knowledge Base - How To:- Add a Variable Delay to the Wipers

Many thanks to Jimi Lawson for the following article

I found that the intermittent position on my wipers was very inflexible, usually too short a delay, resulting in noisy dry wipes.

I set out to see if I could make the delay time variable. The first problem was finding the delay relay, after much searching I found that MR T had hidden the relay inside the switch. Then I had to discover how the delay worked, much head scratching! While working this out, i also found that it relies on a contact in the wiper motor switching as the motor runs to restart the delay sequence.
I found that I was able to make the delay variable between 4 and 30 seconds (much experimenting), tried to get it longer but it meant much more modification of the circuit and tended to be unreliable. 4 to 30 was quite easily achievable. I carried out the mods and installed the switch in my car and it has proved to be both successful and reliable.

If you wish to carry out this modification this is how to do it. Please note this has only been tested on a 1988 NA, other years of MK1 may different, but from looking at the wiring diagrams they seem the same. If you have queries you can contact me here Jimi

You will need the following: -

  • 2 lengths of wire (does not have to be heavy gauge no load involved) about 2ft long
  • A 500Kohm potentiometer
  • A knob to suit the potentiometer
  • Hand tools (screwdrivers etc)
  • Drill of some sort (power/battery/hand)
  • Soldering iron and some skill at using it


Undo the screw and prise up the top, it hinges at the connector end, underneath you will see the back of a small circuit board. Gently lift it up it will pivot on the wire links at the connector end. You should now see this


The only difference will be that you have a resistor soldered in at position R1. Carefully desolder this resistor you will need it again. Replace the circuit board in its original position.
On the back of the circuit board you will be able to see the holes you have removed the resistor from, solder one end of the resistor into the hole nearest to the connector end of the switch. Onto the other end of the resistor solder one of the lengths of wire, insulate the resistor from the circuit board with tape or heatshrink sleeving (I used heatshrink) Into the other hole solder one end of the other length of wire and tape or heatshrink the wires together.

Feed the wires through the white plastic cover at the hinge end (you will need to file a little bit out of the cover to let it close or use the soldering iron to melt a small bit out)
Clip the cover back down and refit the screw. It should now look something like this

You can now refit the switch to the dashboard. Thread the wires down to the position you are going to fit the control. I decided to fit it to the left hand side of the top half of the cover on the steering column. The wires were routed the same way as the existing wiring on the steering column.

Solder the ends of the 2 wires onto your potentiometer. There are 3 solder tags on the potentiometer use the centre (wiper) and any other (it won't matter which one you use, it will just reverse the direction of operation i.e. left for more delay or right for more delay).

You might notice in the above picture that I have used short lengths of wire on the potentiometer and bullet connectors to connect to the longer wires, this was just to make it easier to install and means I don't have to de-solder the wires if I need to remove it.

Drill a hole and install the potentiometer in your chosen position and fit the knob. Here's mine

To use it, put the wiper switch to the intermittent position, with the control set to minimum the delay is the standard 4 seconds, at maximum the delay is 30seconds. The control is fairly linear i.e. halfway approx 15 seconds. I didn't bother with a scale, but it would be quite easy to mark one if you wanted to.

If you do this modification please drop me an PM and let me know how you got on and what you think of it and this how-to.


Jimi Lawson

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Created : 2011-08-27 00:46:30, Last Modified : 2011-08-27 00:46:30

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