28V Type A Alternator Controller: Vreg, OV Relay, Low-OV Warning

SKU: ZA000I.
Category: .

Product Description

28V Type A Alternator Controller: Vreg, OV Relay, Low-OV Warning

What’s included:

  • Installation Drawing
  • Warranty Card
  • Product Eligibility Catalog (PEC)
  • Troubleshooting Notes
  • STC Certificate
  • Instructions For Continued Airworthiness Maintenance (ICA)

Product Features:

Voltage Regulation, IC Sense Referenced

Using the voltage sensed from the OV Relay output, the Regulator keeps the bus voltage constant by controlling the alternator’s field current: increasing it when the system load increases and decreasing it when the load drops. The Regulator controls the field by grounding or opening the one side of the field connected to pin F. The R25V0N ACU works in the one alternator (single engine) application as well as in the dual alternator (single or dual engine application. It is the best replacement for the Prestolite VSF7403 type Voltage Regulator.

Over Voltage (OV) Protection (OVP)

The external OV Protector (OVP) or OV Relay deactivates the Voltage Regulator by removing power to its input and one side of the field if the bus voltage exceeds 16V. This removes the alter-nator field excitation and thus protects sensitive avionics equipment and the battery.

Low Voltage & OV Sensor & Light Output

The unit’s LV indicator will come on when the bus voltage drops below the low voltage point and when the OV Protector (OVP) or OV Relay acctivates.

Other Features:

  • Field Controller Generates Low Heat
  • Externally Adjustable Voltage Regulation
  • Trouble-Shooting Light (TSL)
  • Light Weight and Repairable
  • Increase Regulator Life
  • Not Temperature Sensitive
  • Protects System Against Overexcited Alternator
  • Field Warns of Low & OV Conditions
  • Increased Ease of Ownership
  • Reduced Trouble-Shooting Time & Ownership Cost
  • Reduced Long-term Ownership Cost

Additional Information

Weight1 lbs
Dimensions11 × 8.5 × 5.5 in
Model Number


Voltage Reg. (VR)

28.4V + 0.4V

Max Field Current


Low Voltage Trip (LVI)

24.7V + 0.5V

Over Voltage (OV)

32.0V + 0.8V

Approval Type

FAA-STC Approved

Document Approval

FAA Form 337 Required


VSF7403,2,1,4 & OV RELAY

OEM PN (Electrodelta)

VSF7403A & OS75-28


649684-2, 649440-2 & OV RELAY


LW101079, 77347 & OV RELAY

Replaces OEM PN (PIPER)

550-581 & OV RELAY

Approved Aircraft

310,310P,3100, 320. 401A,4016,402A,4020,414,421,421A,421B.


PA31, PA31-300, PA31-310, PA31-325, PA31-350. PA36-285, PA36-300, PA36-375. PA60-600, PA60-601, PA60-601P, PA60-602P, PA60-700P

Approved Aircraft (SCHWEIZER)


Approved Aircraft (TWIN COMMANDER)


Beech (Beechcraft)

E55, 58, F33A, F33C, A36, A36TC

Warranty Policy

Click the links below to download warranty policy in .pdf format.

Warranty Policy (New Manufactured) PDF Requires Acrobat Reader

Warranty Policy (Recertified) PDF Requires Acrobat Reader

R25V0N - Zeftronics


Click the links below to download the .pdf


Product Connector FAQ PDF Requires Acrobat Reader

General Product

GCU Cross Reference (Coming Soon)

ACU Cross Reference (Coming Soon)

OVR, OVS, Cross Reference (Coming Soon)

How To

How To Read the Cross Reference Chart FAQ (ACU) PDF Requires Acrobat Reader

How To Read the Cross Reference Chart FAQ (GCU) PDF Requires Acrobat Reader