FAQ
TL;DR: On some Micra K12s, moisture triggers phantom wipes; adding a 3 kΩ resistor on the wiper switch PCB stopped it for years for some users—“the problem never happened again.” [Elektroda, diakov, post #17080515]
Why it matters: This FAQ helps 2003–2010 Nissan Micra K12 owners quickly diagnose and fix wipers that start by themselves after rain or washing.
- Symptom snapshot: wipers self-activate only after engine starts, often after rain or a wash. [Elektroda, Rogas28, post #16968343]
- Root cause reported: front washer pump shorts when wet, upsetting the wiper circuit. [Elektroda, Rogas28, post #17080866]
- Low-cost fix reported: solder a 3 kΩ resistor between red and black wires on the wiper switch PCB. [Elektroda, diakov, post #17080515]
- Longevity note: resistor fix held “over two years” for some users. [Elektroda, diakov, post #17081157]
- Edge case: one user saw overnight battery drain after the resistor mod. [Elektroda, dawid5995, post #18377241]
Quick Facts
- Symptom often appears after hand-wash or rainfall and only once the engine is running. [Elektroda, Rogas28, post #16968343]
- Washer pump moisture-short identified; replacing the pump restored normal operation for some. [Elektroda, decybel91, post #18378329]
- Reported part cost: Approx. PLN 25 (used) to PLN 150 (new) for the pump. [Elektroda, Rogas28, post #17080866]
- Resistor remedy: 3 kΩ across red and black on the wiper switch PCB; ample PCB space shown. [Elektroda, diakov, post #17080515]
- Durability: users reported >2 years without recurrence after the resistor mod. [Elektroda, diakov, post #17081157]
What causes my Micra K12 wipers to turn on by themselves after rain or a car wash?
Users traced it to the front washer pump shorting when wet. That interference can trigger the wiper circuit once the engine powers the system. Replacing the pump or isolating its signal addressed the phantom wipes for several owners. [Elektroda, Rogas28, post #17080866]
Why do the wipers start only after I start the engine, not just on ignition?
Owners reported the wipers remain still on ignition, then begin moving after the engine starts. This suggests the fault appears only when engine-run power paths energize, aligning with moisture-related shorts reported by others. [Elektroda, Rogas28, post #16968343]
Is the BCM (Body Control Module) the culprit here?
One commenter suggested a BCM fault, but multiple fixes pointed to the washer pump or stalk circuit instead. If other BCM-controlled features are fine, investigate the pump and wiper switch path first. [Elektroda, piotrekwoj1, post #16969088]
How do I apply the resistor fix on the wiper switch?
Solder a 3 kΩ resistor on the wiper switch PCB between the red (12 V) and black (ground) points. This stabilizes the circuit against the washer pump’s moisture-induced shorting. Photos in the thread show placement and ample board space. [Elektroda, diakov, post #17080515]
Do I need to remove the steering wheel to add the resistor?
At least one user reported removing the steering wheel was required to access the switch comfortably. The work proceeded smoothly once done. [Elektroda, dawid5995, post #18373091]
Will the resistor fix last long-term?
Yes for some. One contributor wrote the resistor solution has worked “over two years,” with no return of phantom wipes. [Elektroda, diakov, post #17081157]
Can the resistor mod cause battery drain?
One user reported the battery discharged overnight after installing the resistor. If this happens, remove the resistor and reassess the washer pump or wiring. [Elektroda, dawid5995, post #18377241]
Does replacing the washer pump actually solve the issue?
Yes for some owners. As one put it, “After the exchange, as he took with his hand,” indicating the phantom wipes stopped once the pump was replaced. [Elektroda, decybel91, post #18378329]
How much should I budget to replace the washer pump on a Micra K12?
One owner faced two parts options: a new OEM-like pump around PLN 150, or a used/swap-in unit for about PLN 25. [Elektroda, Rogas28, post #17080866]
Why do my front wipers stop when I activate the rear washer?
The original poster observed front wipers paused briefly when the rear washer ran, suggesting interaction within the shared control path. This points back to washer-related interference. [Elektroda, Rogas28, post #16969184]
Is this spontaneous-wiper behavior a known Micra K12 issue?
Yes. A member flagged it as a known issue and linked prior discussion dedicated to it. [Elektroda, robin161, post #16969282]
Will pulling fuses stop the wipers from starting by themselves?
The OP tried removing the washer pump fuse and the wiper fuse. The behavior persisted, indicating the root cause sits deeper in the control path. [Elektroda, Rogas28, post #16968343]
What is the BCM in simple terms?
The BCM is the Body Control Module. It supervises various body electronics, including wipers. Some suspected it here, but fixes targeted the pump and switch. [Elektroda, piotrekwoj1, post #16969088]
Is there a quick 3-step process to try the resistor approach?
- Remove trim to access the wiper switch PCB. 2. Solder a 3 kΩ resistor between the red (+12 V) and black (ground) points on the PCB. 3. Reassemble and test wipers and washers for normal behavior. [Elektroda, diakov, post #17080515]
What’s an edge case I should watch out for when modding the switch?
After a successful initial result, one user later experienced overnight battery drain. If you see this, revert the mod and inspect the pump. [Elektroda, dawid5995, post #18377241]
If replacing the pump worked at first but the problem returned, what next?
One owner said two pump swaps didn’t hold. They then added the 3 kΩ resistor at the switch and reported over two years trouble-free. [Elektroda, diakov, post #17081157]
