1. Intermittent wiper controller.
+12 VDC on
wiper switch
On-off switch
500k 10k
47k
2N4403
2N4401
Normally open contacts
3.3k
100k +
100 uf To wiper moter
12 volt relay
1N4002
The intermittent wiper circuit shown above causes the auto's windshield wipers to wipe
once every several seconds instead of constantly wiping. The circuit may be added to
older cars to provide the intermittent function or it may be used to replace broken wiper
circuits in modern cars. The delay is continuously adjustable with the potentiometer but
switch selected fixed resistors may also be used, if desired. The circuit should be
connected to +12 volts at the same point as the original wiper power switch so that the
proper fuse protection is preserved. The 12 volt relay should have contacts rated for a few
amps since the wiper motor will draw a considerable start current but most automotive
relays are adequate. The circuit should be quite trouble-free and will work on the first try
if no wiring errors are made!