Understanding Grid Heater Relay Issues in the JCB 300T and Volvo 135C

[MikePhua]

Grid heaters play a crucial role in improving engine performance in cold weather conditions by assisting with the cold start process. The JCB 300T skid steer and the Volvo EC135C compact excavator, both popular models in the construction and agricultural sectors, rely on a grid heater relay to regulate the function of their grid heaters. However, like any electrical component, the grid heater relay can sometimes fail, leading to engine starting issues and performance problems. This article explores common problems with grid heater relays, troubleshooting methods, and solutions to get these machines running smoothly in cold conditions.

The Role of the Grid Heater Relay
Grid heaters are used in diesel engines to assist with cold starts by heating the intake air before it enters the engine. This helps to improve combustion, making it easier to start the engine in cold temperatures. The grid heater relay is an electrical component that controls the operation of the grid heaters. It acts as a switch, allowing power to flow to the grid heaters when needed, and cutting off the power once the engine reaches a certain temperature.
For example, a fleet manager working in a region with extremely cold winters noticed that their JCB 300T skid steer was having difficulty starting during the colder months. After some investigation, they discovered that the grid heater relay was malfunctioning, which prevented the grid heaters from activating properly. Replacing the relay solved the cold start problem and restored reliable engine performance.

Common Grid Heater Relay Issues in the JCB 300T and Volvo 135C

1. Grid Heater Relay Fails to Activate
   

One of the most common issues with grid heater relays is that they fail to activate, preventing the grid heaters from turning on when needed. This can lead to difficulty starting the engine, especially in cold weather conditions.
An operator using a Volvo EC135C excavator faced this issue when the machine would not start in cold weather, despite following the usual cold start procedures. Upon inspection, it was found that the relay was not sending power to the grid heaters, likely due to a faulty relay or a problem with the relay's electrical contacts.
Solution: If the grid heater relay fails to activate, start by checking the relay's electrical connections. Inspect the relay for any visible signs of wear or corrosion. If the relay seems faulty, replace it with a new one to restore proper function.

1. Intermittent Operation of the Grid Heater Relay
   

Another issue that can arise with the grid heater relay is intermittent operation. In this case, the relay may sometimes work correctly, allowing the grid heaters to activate, but at other times, it may fail to provide power to the heaters. This can make starting the engine unpredictable and unreliable, especially in colder temperatures.
A construction company operating multiple JCB 300T machines reported experiencing intermittent grid heater relay operation. The issue was traced to a faulty contact within the relay, which caused the connection to be unreliable. Once the relay was replaced, the cold start issue was resolved, and the machine started reliably every time.
Solution: Intermittent operation can often be caused by poor electrical connections or internal relay faults. Check the relay for corrosion or signs of wear. If the problem persists, consider replacing the relay and ensuring all connections are clean and secure.

1. Blown Fuse or Damaged Wiring
   

Sometimes, a blown fuse or damaged wiring can prevent the grid heater relay from working. This can occur if there is a short circuit or if the grid heater system is drawing too much current. If the fuse is blown, the grid heaters will not receive power, and the engine may struggle to start.
An operator working with a JCB 300T skid steer faced a situation where the machine failed to start due to a blown fuse in the grid heater circuit. After replacing the fuse, the grid heater relay began working again, and the machine started with no issues.
Solution: Check the fuses associated with the grid heater relay and the heater circuit. If a fuse is blown, replace it with one of the correct rating. Also, inspect the wiring for any signs of damage or short circuits, and repair or replace the damaged wiring as necessary.

1. Grid Heater Relay Control Module Failure
   

Some machines, including certain models of the Volvo EC135C, have a control module that works in conjunction with the grid heater relay to regulate the heater's function. If the control module fails, it can prevent the grid heater relay from receiving the correct signals to activate. In these cases, the relay might fail to work at all, leading to cold start issues.
A fleet supervisor working with a Volvo EC135C excavator encountered this issue when the grid heater relay would not respond. After a detailed diagnostic, they determined that the control module had failed and was not sending the proper signals to the relay. Replacing the control module restored normal grid heater operation.
Solution: If the grid heater relay seems fine but still fails to activate, the issue may lie with the control module. Inspect the module for faults and replace it if necessary. Ensure that the control module is receiving the correct input from the engine’s temperature sensors and other components.

Troubleshooting the Grid Heater Relay: A Step-by-Step Approach

1. Check the Relay for Power
   

Use a multimeter to check if the grid heater relay is receiving power. If there is no voltage at the relay’s input terminals, the issue may lie with the power supply or fuse. If the relay is receiving power but not activating the grid heaters, the relay itself may be faulty.

1. Inspect the Relay’s Connections
   

Ensure that all electrical connections to the grid heater relay are clean, tight, and free from corrosion. Loose or corroded connections can prevent the relay from operating correctly. Clean the terminals if necessary, and ensure that the relay is securely mounted.

1. Test the Grid Heater Circuit
   

If the relay seems to be working properly, test the grid heater circuit itself. Use a multimeter to check for continuity in the circuit and verify that the grid heaters are receiving power when the relay is activated.

1. Check the Fuse and Wiring
   

Inspect the fuse associated with the grid heater system, as well as the wiring for any signs of damage or short circuits. Replace any blown fuses and repair any damaged wiring to restore full functionality.

1. Test the Control Module (if applicable)
   

If your machine is equipped with a control module that regulates the grid heater relay, test the module to ensure it is functioning correctly. Verify that the module is receiving signals from the temperature sensors and sending the appropriate commands to the relay. Replace the module if necessary.

Preventing Grid Heater Relay Problems

1. Regular Maintenance Checks
   

Regular maintenance of the grid heater system can help prevent relay problems. Ensure that the system is free from debris, the wiring is intact, and the fuses are in good condition. Periodically check the relay for signs of wear or corrosion and replace it as necessary.

1. Use the Correct Fuse Ratings
   

Always use fuses with the correct amperage rating for the grid heater system. Using fuses with too high or too low a rating can cause issues with the grid heater relay and other electrical components.

1. Keep the Electrical Connections Clean
   

Corroded or loose electrical connections are one of the leading causes of grid heater relay problems. Clean and tighten all connections regularly to ensure the system is working as intended.

1. Use Quality Replacement Parts
   

When replacing the grid heater relay or associated components, always use high-quality parts that meet the manufacturer's specifications. Using substandard parts can lead to further electrical issues and increased downtime.

Conclusion: Ensuring Reliable Cold Starts with a Functional Grid Heater Relay
The grid heater relay is an essential component for ensuring reliable cold starts in machines like the JCB 300T skid steer and the Volvo EC135C excavator. When the relay malfunctions, it can lead to difficult or unreliable starts, especially in cold weather. By following a systematic troubleshooting approach, operators and fleet managers can identify and fix issues related to the grid heater relay, ensuring that the machine starts smoothly even in challenging conditions.
Regular maintenance, including checking fuses, inspecting wiring, and replacing faulty relays, can help prevent grid heater relay problems and ensure that your machines are ready for work whenever you need them. Whether you're working in freezing temperatures or managing a fleet of construction equipment, understanding how to troubleshoot and maintain the grid heater relay is key to keeping your machines running efficiently.