Skip to content

2.5 Horn System

PIAA 85115 Superior Bass Horn

Type: Dual Tone Horns

Model: 85115

Part Number: 85115

Manufacturer: PIAA

Product Page: PIAA Superior Bass Horn 85115

Mounting: Engine bay

Power Source: PMU Out 18 (7A capacity, CONSTANT)

Specifications

  • Current draw: 2.7A per horn × 2 = 5.4A total
  • Ground: Chassis ground (engine bay)

Control

Button: Momentary push button (normally open) on steering wheel PTT bracket

PMU Configuration:

  • Input: In 1 (horn button signal)
  • Output: Out 18 (7A capacity, powers horns directly)
  • Logic: When In 1 closes, Out 18 activates (no external relay needed)
  • Power: CONSTANT (works with ignition off for safety)

Wiring Configuration

START battery CONSTANT → PMU → Out 18 → PIAA Horns (5.4A) → Chassis Ground
                          ↑
                      Horn Button → In 1 (trigger)

Power Flow:

  1. START battery+ → CONSTANT bus → PMU
  2. Horn button (steering wheel) → PMU In 1 (trigger signal)
  3. PMU Out 18 activated when In 1 closes
  4. PMU Out 18 → PIAA horns (5.4A) → chassis ground (engine bay)

Notes:

  • PMU Out 18 switches directly (no external relay needed)
  • Works with ignition off (CONSTANT power for safety)

Outstanding Items

None - design complete. See installation checklist for build tasks.