Case IH 3269 – Engine ECU (EDC): Grid Heater Switch On Test - Voltage Drop Too High

The ECU performs a self-test on the grid heater circuit. A 'Voltage Drop Too High' indicates excessive electrical resistance in the high-current circuit, meaning voltage reaching the heater or returning is dropping below acceptable thresholds, preventing efficient operation.

• Magnum 235-340 (Series 4)
• Steiger series
• Puma series (e.g., Puma 165, 185)
• Axial-Flow series (e.g., 6140, 7140, 2577, 2588)
• 580M Series 2 Loader Backhoes
• TR320 Compact Track Loaders

1. 1

   Inspect the heavy-gauge cables running from the battery to the grid heater relay, and from the relay to the intake manifold grid heater for melted insulation, loose retaining nuts, or heavy corrosion.

2. 2

   Check the main grid heater fuse (often a 300-amp mega fuse located near the battery or junction block) to ensure it is intact.

3. 3

   Check for battery voltage at the input stud of the grid heater relay. Command the relay ON and measure the voltage at the output stud. A significant voltage drop indicates burnt internal contacts.

4. 4

   Disconnect the power cable from the grid heater element on the intake manifold. Use a multimeter to measure the resistance between the heater terminal and a clean engine ground. An open circuit or unusually high resistance means the element is burnt out.

1. 1

   Disconnect Power

   Disconnect the negative battery cable(s) to prevent accidental arcing or electrical fires.

2. 2

   Clean Connections

   If the diagnostic checks revealed loose or corroded connections, remove the retaining nuts, clean the ring terminals and studs with a wire brush, and re-torque them to OEM specifications.

3. 3

   Replace the Relay

   If faulty, disconnect the small ECU control wires from the relay. Unbolt the heavy-gauge power cables from the relay studs. Remove the relay mounting bolts and remove the old relay. Install the new relay, reattach the cables, and tighten securely.

4. 4

   Replace the Grid Heater Element

   If faulty, remove the charge-air piping/hoses connected to the intake manifold inlet. Disconnect the heavy-gauge power cable from the grid heater element. Unbolt the grid heater module from the intake manifold. Clean the mating surfaces on the intake manifold thoroughly. Install the new grid heater element using new gaskets (usually 0.3mm thick). Reinstall the mounting bolts, reconnect the power cable, and reattach the intake piping.

5. 5

   Reassembly and Testing

   Reconnect the negative battery cable. Use a diagnostic tool (like CNH EST) to clear the fault codes. Cycle the ignition key to allow the ECU to perform the Grid Heater Switch On Test and verify the code does not return.