Wiper and Washer Systems: Description and Operation

Washer Operation
Pushing the wiper/washer control knob sends current from Fuse 1 (50 A)Eng Comp PDB through the washer switch to the windshield washer pump and GEM/CTM. Normal wiping action occurs during washing when the wiper switch is in LO or HI. If the wiper switch is in OFF or INT, the wiper hi-lo relay (operated by the GEM/CTM) applies power to low speed terminal of the wiper motor; the wipers operate in low speed. When the washer button is released, low speed operation continues for several cycles to dry off the windshield. The wipers then return to OFF or INT operation.

LO/HI Speed Wiper Operation
When the wiper switch is in the LO (or HI) position, the GEM/CTM activates the wiper hi/lo relay which activates the wiper motor.

The GEM/CTM responds to the windshield wiper control commands by interpreting inputs from the steering column seven-position delay/wash and four mode select position switches.

The GEM/CTM relay drivers control three external relays: wiper hi/b relay, dynamic run/park relay and washer pump relay. When the washer switch is activated longer than 220 ms, the wash and wiper (low- speed) functions are provided until the switch is released. The release of the switch will be followed by three low-speed wipes. If the switch is pressed between 100 ms and 220 ms (with the mode in the OFF position), the wiper system will provide one wipe at low speed with no wash.

Interval Wiper Operation
During interval operation, the wipers make single wipes at low speed separated by a variable length pause.

When first switched to INT position, the GEM/CTM activates the interval timer located in the multifunction switch. The interval timer momentarily closes the wiper switch (integral to multi-function switch), energizing the wiper circuit of the GEM/CTM. Current flows from the GEM/CTM to the wiper motor lowspeed terminal through the wiper hi-lo and wiper run/park relays. Ground is connected to terminal C of the wiper motor.