B1420

Code

FIAT B — Body

Front right electric window motor short to positive

Brand: FIAT

Type: B — Body

Views: UK: 2 EN: 7 RU: 4

AI status

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Page language: EN

Causes

Damaged or chafed wiring harness causing insulation failure and contact with battery positive or constant B+ feed
Corroded or contaminated connector at the front right window motor or switch (water ingress)
Faulty front right window motor with internal shorted windings or commutator short to battery
Faulty window switch or shorted switch wiring feeding B+ onto the motor output circuit
Faulty BCM/window module driver providing permanent B+ or failing to switch/monitor the circuit
Aftermarket alarm/remote or incorrect wiring interfering with the window circuit

Symptoms

Front right window will not operate normally (stuck open or closed)
Window runs or attempts to move without switch input or runs continuously
Blown fuse for windows or repeated fuse failures
Burnt smell, smoke, or heat at the door harness or motor area
BCM/memory loss or other body electrical faults present
Stored DTC B1420 and possibly related body/window codes

What to check

Read and record freeze-frame data and any additional DTCs with a scan tool; clear code and attempt to re-create fault
Visually inspect door harness at hinge, connectors, and motor for damage, corrosion, melted insulation, or water ingress
Check related fuses and relays for signs of overheating or deformation
With ignition off, disconnect the motor connector and inspect pins for damage and corrosion
Measure voltage at the motor connector with ignition off and with switch operated (compare to battery voltage)
With motor disconnected, check continuity between motor positive control pin and battery positive to detect an unintended short

Signal parameters

Battery voltage (resting): ~12.0–12.8 V (vehicle off); ~13.5–14.8 V (engine running)
Motor output voltage when commanded: approx. battery voltage (~12–14 V) applied to one motor terminal while the opposite is switched to ground; polarity reverses for up/down
No-command voltage at motor control terminal: ~0 V (should not be continuous B+ when module is inactive)
Typical running current: ~5–20 A (varies by vehicle/motor). Stall/peak current can be significantly higher (may exceed 30 A) — check manufacturer specs
Resistance of a healthy motor (cold, across terminals): typically low ohms (exact value manufacturer-specific)

Diagnostic algorithm

Safety first: disable the battery negative terminal when performing repairs that expose wiring or connectors to avoid short/airbag issues.
Connect a diagnostic scan tool, read all stored codes and freeze-frame data; note condition when fault occurred.
Visually inspect the front right door harness, connectors, switch and motor for obvious damage, burns, corrosion or water entry.
Check fuses/relays for the window circuit; replace if evidence of failure but do not drive replacement until root cause found.
With ignition off, disconnect the motor connector. Inspect pins and measure for continuity between the motor positive terminal and battery positive; if continuity exists when motor is disconnected, trace wiring to locate short.
With motor disconnected, operate the window switch while measuring voltage at the BCM/module output connector: verify no permanent B+ present when output should be off and correct polarity when commanded.
If a permanent B+ is present at the module output (motor disconnected), suspect BCM/module or upstream short — verify wiring integrity back to the module.
If the module output only supplies B+ with switch command and no B+ at rest, bench-test the motor by applying battery directly (observe current draw and direction). Replace motor if it shows internal shorting, abnormal current or excessive heating.
If wiring is damaged at the door hinge area, repair harness with appropriate automotive-grade repair (solder or approved splices, heat shrink, protective conduit) and re-test.
After repair, clear codes and fully cycle the window several times while monitoring current/voltage; ensure no recurrence of fault and no blown fuses.
If BCM output appears to be faulty after wiring and motor verified good, consult manufacturer guidance for BCM diagnosis/repair or replacement.

Likely causes

Wiring insulation damage at door hinge/dut/door harness causing short to constant B+
Corroded/pinned connector at the motor/switch allowing battery feed on the control pin
Failed motor with internal short

Fault status

⚠️ Status

Stored fault: Front right window motor circuit short-to-positive detected by BCM. Circuit disabled until repair; driver may experience inoperative or uncontrolled window and related fuse/driver issues.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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