It looks like a wiring issue of the delay unit. When the delay cuts off power, there should be still park power available to the motor.
By the term park power i mean the power that is available when the master switch is off, and is controlled by the park switch in the motor.
I repaired mine by finding the end of the pipe in the wire harness by the motor and fitting a straight plastic joint from an Aquarium air system and some clear air pipe from the same system. Worked a treat.
Regards Terry H
All fixed. Replaced brush/contact unit and armature (over heated at some stage destroying insulation of the windings). Replaced crank arm as plastic bush missing on wheel pivot. New foam and valve in delay unit. Replaced rubber mounting bobbins. Cleaned all contacts and housing with contact cleaner. Cleaned everything in solvent and repacked with lithium based grease. Installed suitable spring on delay cam slider. Vacuum tube and regulating valve on steering column in working order. Variable wipe adjustable between 1 and 11 seconds. (should be ample for a car that wont go out in the rain.)
A big thanks to Steve from the local Rover club for the donor wiper assembly which had just the right serviceable parts to get one unit going.
It sounds like the only problem you have is with the self parking switch. On slow and fast settings the self parking switch is unused but during delay, as soon as BOTH the self parking switch and the delay governor have changed state, you are relying on the self parking switch to supply power. If it does not then your wipers will stop midway on intermittent wipe, and also the self parking function will fail, both of which you say are happening.
The wiper connections are highlighted above, during parking after switching off the wipers. The 12V power comes in on pin 4, through the parking switch and exits on pin 2. The other end of the pin 2 connection goes to pin 6 of the wiper switch on the dashboard, exiting on pin 4, then on to pin 5 on the wiper connections to the slow speed wipers. The image below shows the connection numbers of the wiper connector.
First you need to check for 12V power on pin 4 of the wiper connections, and again on pin 2 when the wipers are in operation. On pin 2 there should initially be no voltage until you switch on the wipers, then as they move off the voltage should appear. For you this would be easiest to do in delay mode. If the voltage is missing then the fault is with the parking switch as I suspect.
If the voltage is present on pin 2, then check pin 5. If there is no voltage on pin 5 then the wiper switch on the dashboard, or the wires on pins 4 and 6 of the wiper switch, needs attention. Check the image below for the wiper switch connections.
All the information above is for my 3500S, but hopefully it will give you an idea of what to look for.
I guess it could be security settings on the browsers that cannot see the images (Internet Explorer is well known for it's security vulnerabilities). The picture URL's begin with http:// as opposed to the more secure https://
I did try to insert an image to this post using the original http:// URL for an image and it gave me an error message:
However, when I tried the secure URL it adds the image.
Although I am quite willing to edit the post and change all of the image URL's I cannot save the post as there seems to be a character limit of 10000 which is set by the site.
Firefox works fine, thanks. Have saved whole first page, so now I have a reference. My air nipple on the delay unit is broken off, and the long light spring was sitting on the insulation - lucky I noticed it!
Reassembled. Still experimenting with the foam - think its working with some bubbles from bubblewrap in there. Currently when the plunger is pushed fully in, and the bleed nipple blocked, the plunger comes out ~8mm, and pretty much stops until the bleed nipple is opened - does that sound about right? If not, will have to keep looking for some thing else. Suspect a small spring would work, like one the motor brush springs. Found where the spring goes too! Ran a thin strip of emery through the contacts inside the delay unit, resistance now around 1ohm - probably limit of the meter.