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93 civic cx cdm
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49 Posts
Discussion Starter #1
washer pump works fine with car battery (12v) connected to it, pumps water fine. however, when connected normally, water pump fails. measured voltage between water pump wires (with water pump disconnected and switch) and shows 10-12v (as would be expected from battery). when connecting the water pump, the read voltage drops to 1v or so. hence there is current and thus power applied to pump. to sum up the voltage is being supplied, the water pump is working on car battery (12v), but the water pump does not work when connected normally.

i don't understand whats wrong. not enough current ? but then voltage is 12v and load resistance is the same. unable to supply enough power by battery ? but then when connected to the battery the pump works fine - same battery in car being used.

help please
 

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5,880 Posts
leave pump disconnected, have probes in washer plug. Have a friend activate washer pump while you measure voltage.

Also, measure ground resistance during operation compared to battery ground.
 

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BATSLOMAN GIVES NO FUCKS.
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4,110 Posts
is there a relay for the washer pump?
 

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89 EF 4wd sedan
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544 Posts
Sounds like a ground issue. To confirm, turn the key to IGN 2, connect the hot wire to the pump from the harness, but use a wire to ground the negative terminal of the motor to the chassis. Pump should turn on.

If that's the problem, either there's a break in ground wire (from pump to washer switch) or perhaps the contacts in the switch are corroded (the multifunction switch behind the steering wheel)
 
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