Variable intermittent wipe - mk1 Yaris.

[jonquirk]

My biggest gripe with my Yaris is the single speed rear wiper: rarely is it possible to keep it running for more than a few seconds before the screen is too dry. I end up turning it on and off almost constantly when I am driving on a wet motorway. Time to do something about it.

First step was to buy a wiper stalk for a 2003 Corolla from eBay. The Toyota wiper stalk has the front intermittent relay built in to it: fixed interval on the Yaris, variable interval via a swivelling ring on the Corolla item. This is a straight replacement for the Yaris stalk. It also has the switch position for rear intermittent wipe on the stalk. Of course at this stage it does nothing.

i spent a while studying the wiring diagrams for Yaris and Corolla until I understood how to proceed. There is a variable intermittent wiper relay available that has its interval programmed by switching the wiper on for one sweep, switching the wipers off and then switching them back on when required. The relay records this time and uses that for the delay interval until the ignition is switched off or a new interval is programmed.

In an ideal world one could just plug this in and be done. A lot of vehicles with separate fixed interval intermittent relays can indeed use this relay simply by swapping it for the old one. For the Yaris rear wiper it was a bit more complicated. The relay is designed to switch the live feed to the wiper motor on and off at the programmed interval. The Yaris rear wiper has 12V at the motor all the time the ignition is on. The motor is operated by managing the connection to ground (0V). Also the plug to the wiper stalk on the Yaris only has pins 2-9 present in a ten pin plug. I had to add pin1 to the plug and tap into the wiring on pin 2 (motor earth), pin 5 (ground), pin 8 (12V from ignition switch), 

When continuous wipe is selected pin 2 is connected to pin 5 thereby completing the circuit from the motor and wiping occurs. Selecting intermittent wipe connects the new pin 1 to pin 5. I used a relay: the coil is connected to pin 8 (12V) and pin 1. The relay contacts are connected to pin 8 (12V) and the control pin on the wiper relay. The output from the wiper relay switches another relay that connects the motor to ground every time the wiper relay triggers.

i am pleased to report that it all works beautifully. All I need now is some rain and a reason to be on the road.

Next project will be a light in the boot, possibly combined with replacing the rear view mirror for one with map reading lights built in.

if any one knows of a permanent live 12V connection at the back of the car I would be grateful to hear about it. Failing that I will either have to run power from the dashboard or run a feed from the dome light by partially dropping the headlining.

[jonquirk]

I have an answer to the question I posed above: the live feed to the dome lamp (blue with yellow tracer) runs from behind the right hand rear light unit, easily accessible to provide power for load space illumination. More information once the lights and door switch I ordered have arrived.

[Ricochet1]

sounds a worthwhile mod.

[Gch01]

Hiya mate do you have any more images of the wiring you did for this?