Wipe and wait

My car has a 4-position windshield wiper stalk; off, intermittent, slow, fast.

While the motor needs to be pulled and serviced because there’s little difference between slow and fast, the intermittent wipe had always been somewhat pathetic.

Selecting intermittent would make the relay click, and as soon as the wipers returned to the parked position, click again and they would almost immediately wipe again.

Pulled the dash shroud down and located the clicking box at the top left. (Top right is the key-in/seatbelt buzzer, bottom left the cruise control stalk, above that with the finned heat sink the dashboard dimmer control).

relay delay box

Took the circuit board out and drew up the circuit diagram by following the traces, to get a better understanding of the circuit and its method of operation.

board

Culprits were most likely the electrolytic capacitors. One had a high ESD and the other was meant to be 22uF, it measured in at about 100nF. Replaced them both. Now the wipers wipe and wait about 5 seconds before wiping again on intermittent, and added bonus, they now wipe 3 times after spraying screenwash onto the screen. Not bad for 45 minutes’ work and spares I had in stock.

Leave a Reply