geobloke wrote:

When you say not turning off, do you mean they do not park or they keep on going after you cancel the switch?

blackwolf wrote:

It is possible that either the stalk switch, the park switch, or even the "relay" (which isn't really a relay in the conventional sense) could be causing this, it is hard to say which is most likely without a little more information.

The park switch is a single pole double throw switch, with the common pole connected via the timer unit (aka "relay") to the stalk switch. When the stalk switch is in the "wipers off" position the common pole is connected (via the timer unit of course) to the normal (slow) speed brush of the motor. When the stalk switch is in either of the "run" positions (i.e., "normal" or "fast" speeds) the connection between the normal speed brush and the timer unit is open circuit.

The common pole of the park switch is switched between a ground connection (when the wiper sweep in in the parked position) and live feed (when the wipers are anywhere other than in the park position).

Common problems cause by a sticking park switch are either the wipers never stop running (until the ignition is switched off) which is the result of the park switch sticking in the closed-to-live (i.e., not parked) position, or the wipers don't park correctly and simply stop wherever they are when the stalk switch is set to the off position, which is caused by the park switch failing to close the contacts into the closed-to-live position. Fortunately the only other failure mode of the switch, the stuck in the closed-to-earth mode, is virtually impossible, but if it did happen there is likely to be a leakage of smoke from somewhere until a fuse blows.

I mentioned above that the connection from the common pole of the park switch is connected to the stalk switch via the delay unit (aka "relay"), and the reason for this is to support the "wipe-on-squirt" and the "intermittent wipe" functions, which are both effected in a similar manner.

When the squirt switch is pressed, the switched live from the squirt switch to the washer motor also connects a live feed to the delay unit, and this activates a relay internal to the delay unit which disconnects the normal speed motor brush from the park switch common pole, and instead connects it (the normal speed motor brush) to a live feed within the delay unit. The relay is energised by a timer circuit implemented by means of solid-state electronics within the delay unit which maintains the relay activation for a set period after the squirt switch is released, and as a result after the set period the relay de-energises and the brush feed is one again connected to the park switch common pole in the normal manner, and the normal park function works exactly as it does when the wipers are switched off after a continuous wipe (using the stalk switch) operation.

When the stalk switch is set to "intermittent wipe", a feed from the stalk switch energises another of the input pins on the delay unit, and solid state electronics once again cause a periodic activation of the same internal relay used with the squirt function. The pulse applied to the relay is of sufficient duration to move the wipers away from the park position only, the relay then deactivates and the remainder of the wiper sweep is provided by the normal wiper park function described in the first paragraphs above. On a standard relay the frequency of the pulses is fixed (so the interval between wipes is fixed) but with a less antiquated delay unit, such as the VW "99" unit, the pulse frequency can be set by driver demand allowing the variable intermittent function.

Hopefully it is clear from the above (if you've stuck with it!) that the same mechanism is used to park the wipers under all circumstances - there is only one park mechanism - so a faulty park switch will generally be apparent for normal wipe functions, squirt functions, and intermittent functions. A "stuck-to-live" fault will cause the wipers to run continuously and is hard to miss. A "stuck open circuit" fault can be more confusing, because I have come across delay units where the relay activation just happens to be of exactly the right duration for a single sweep and will stop the wipers, coincidentally, in the park position. This can be misleading when fault finding.

The symptoms you describe are inconsistent, suggesting an intermittent fault. The most likely part of the system to cause intermittent faults is the park switch, and it is also probably the cheapest component to swap on an ad-hoc basis. Unfortunately it isn't the easiest to get to, but it would be my starting point, and I feel that it is very likely to be the problem.

You could eliminate the delay unit as the cause if you remove it and carefully connect receptacles 2 and 5 in connector C0303 (the delay unit socket). This will completely remove the wipe-on-squirt and intermittent functions, and the wipers should work as simple, old-fashioned, off/normal/fast wipers with normal parking. If they do not park properly in this mode, the fault is overwhelmingly likely to be the park switch (but could, but is highly unlikely to, be the stalk switch).