Introduction
The B1968 diagnostic trouble code (DTC) indicates a malfunction within the A/C water pump detection circuit in a vehicle's climate control system. This circuit is responsible for monitoring the operation of the A/C water pump, which circulates coolant through the auxiliary A/C system, often found in vehicles with rear climate control or those designed for hot climates. A failure in this circuit can lead to reduced or nonexistent A/C performance, especially in the rear of the vehicle, and could potentially lead to overheating issues if the auxiliary cooling system isn't functioning as intended. Addressing this issue promptly is crucial to maintaining passenger comfort and preventing further damage to the A/C system.
B1968 A/C Water Pump Detection Circuit Failure: Comprehensive Overview
| Topic | Description | Potential Causes |
|---|---|---|
| A/C Water Pump Function | Circulates coolant through an auxiliary A/C evaporator core, typically located in the rear of the vehicle. This enhances cooling performance, especially in vehicles with large cabins or those operating in high ambient temperatures. | Pump failure (mechanical or electrical), clogged coolant lines, air pockets in the system, low coolant level. |
| Detection Circuit Purpose | Monitors the A/C water pump's operation, ensuring it's functioning correctly. The circuit typically uses a voltage or current signal to verify the pump's activity. If the signal is outside the acceptable range, the B1968 code is set. | Wiring issues (shorts, opens, corrosion), faulty A/C water pump sensor, malfunctioning A/C control module (HVAC control unit), poor electrical connections, damaged wiring harness. |
| Symptoms | Reduced or no A/C performance in the rear of the vehicle (if equipped), potential overheating in extreme conditions, A/C system cycling on and off erratically, illuminated A/C warning light, the B1968 DTC stored in the vehicle's computer (PCM or BCM). | A/C system problems unrelated to the water pump (e.g., refrigerant leak, compressor failure), blocked airflow to the rear evaporator, faulty temperature sensors, incorrect A/C system settings. |
| Diagnostic Steps | Visual inspection of wiring and connectors, testing the A/C water pump's operation, checking the voltage and ground at the pump connector, using a scan tool to monitor A/C system parameters, performing a circuit test to identify shorts or opens. | Incorrect diagnostic procedures, misinterpreting scan tool data, overlooking simple problems (e.g., blown fuse), failing to properly test the A/C water pump, assuming the A/C control module is faulty without proper verification. |
| Common Fixes | Replacing the A/C water pump, repairing or replacing damaged wiring, cleaning corroded connectors, replacing the A/C water pump sensor, reprogramming or replacing the A/C control module (in rare cases). | Using incorrect replacement parts, improper wiring repairs, failing to address the root cause of the problem (e.g., ignoring a coolant leak that caused the pump to fail), inadequate system flushing after replacing the pump. |
| Related Codes | Other A/C system codes (e.g., refrigerant pressure codes, compressor codes), coolant temperature codes, electrical system codes. | Intermittent electrical problems, underlying mechanical issues with the A/C system, problems with other sensors or actuators in the climate control system. |
| Component Location | The A/C water pump is typically located near the auxiliary evaporator core, often in the rear of the vehicle. The wiring and connectors associated with the detection circuit will be in close proximity to the pump and the A/C control module. | Difficulty accessing the A/C water pump due to its location, hidden wiring harnesses, corroded connectors that are difficult to disconnect. |
| Voltage Requirements | Typically, the detection circuit operates on a 5V reference voltage. The signal voltage returning to the control module will vary depending on the pump's operating status. | Voltage drop due to corroded connections, short to ground, open circuit. Inaccurate voltage readings can lead to misdiagnosis. |
| Resistance Checks | Resistance checks of the A/C water pump motor and the wiring harness can help identify shorts or open circuits. Compare resistance values to manufacturer specifications if available. | Using an incorrect multimeter setting, inaccurate resistance readings due to poor connections, misinterpreting resistance values. |
Detailed Explanations
A/C Water Pump Function: The A/C water pump is an electric pump that circulates coolant through a secondary A/C evaporator core. This is most often found in vehicles with a rear A/C system, like SUVs or minivans, but can also be present in vehicles designed for particularly hot climates to increase overall cooling capacity. The pump ensures that coolant is continuously flowing through the rear evaporator, allowing it to effectively cool the air being circulated to the rear passengers. Without a functioning A/C water pump, the rear A/C system will likely provide little to no cooling.
Detection Circuit Purpose: The A/C water pump detection circuit is designed to monitor the operational status of the A/C water pump. This circuit typically works by sensing the voltage or current draw of the pump when it's running. The A/C control module (HVAC control unit) expects to see a specific signal from this circuit when the A/C system is active and the pump should be running. If the control module doesn't receive the expected signal, it interprets this as a malfunction in the pump or the circuit itself and sets the B1968 code.
Symptoms: The most noticeable symptom of a B1968 code is a lack of cooling from the rear A/C vents (if the vehicle is equipped with a rear A/C system). Other symptoms may include the A/C system cycling on and off sporadically, an illuminated A/C warning light on the dashboard, or, in extreme cases, a slight risk of engine overheating if the auxiliary cooling system is a critical part of the vehicle's overall cooling strategy. It's important to note that the front A/C may still function normally, even with a failed rear A/C water pump.
Diagnostic Steps: The diagnostic process for a B1968 code involves a systematic approach. Start with a visual inspection of the wiring and connectors associated with the A/C water pump and its detection circuit. Look for signs of damage, corrosion, or loose connections. Next, test the A/C water pump itself to ensure it's functioning correctly. Use a multimeter to check for voltage and ground at the pump connector when the A/C system is activated. A scan tool can be used to monitor A/C system parameters and identify any abnormalities. Finally, perform a circuit test to check for shorts or opens in the wiring between the pump, the sensor (if equipped), and the A/C control module.
Common Fixes: The most common fixes for a B1968 code include replacing the A/C water pump, repairing or replacing damaged wiring, cleaning corroded connectors, and replacing the A/C water pump sensor (if one is present). In rare cases, the A/C control module itself may be faulty and require reprogramming or replacement. Always address the underlying cause of the problem to prevent future failures. For example, if a coolant leak caused the pump to fail, repair the leak before replacing the pump.
Related Codes: While the B1968 code specifically points to a problem with the A/C water pump detection circuit, other related codes may also be present. These could include other A/C system codes (e.g., refrigerant pressure codes, compressor codes), coolant temperature codes, or electrical system codes. These related codes can provide valuable clues to the root cause of the problem and help narrow down the diagnostic process.
Component Location: The location of the A/C water pump varies depending on the vehicle make and model, but it's typically found near the auxiliary evaporator core, often in the rear of the vehicle. The wiring and connectors associated with the detection circuit will be in close proximity to the pump and the A/C control module. Consult the vehicle's service manual for specific location information.
Voltage Requirements: The A/C water pump detection circuit often relies on a 5V reference voltage supplied by the A/C control module. The signal voltage returning to the control module will vary depending on whether the pump is running or not. A multimeter can be used to check for the presence of the 5V reference voltage and to measure the signal voltage.
Resistance Checks: Performing resistance checks on the A/C water pump motor and the wiring harness can help identify shorts or open circuits. Disconnect the pump and measure the resistance across its terminals. Compare the reading to the manufacturer's specifications if available. Also, check the resistance of the wiring harness to ground to identify any shorts.
Frequently Asked Questions
What does the B1968 code mean? It indicates a malfunction in the A/C water pump detection circuit, signaling that the vehicle's computer isn't receiving the expected feedback from the pump.
Can I still drive my car with a B1968 code? Yes, but you may experience reduced A/C performance, especially in the rear of the vehicle, and potentially overheating in extreme conditions.
How do I fix a B1968 code? Diagnose the problem by inspecting wiring, testing the pump, and checking the circuit. Common fixes include replacing the pump, repairing wiring, or cleaning connectors.
Is the A/C water pump the same as the engine's water pump? No, the A/C water pump is a separate pump used to circulate coolant specifically for the auxiliary A/C system, usually in the rear of the vehicle.
Can a blown fuse cause the B1968 code? Yes, a blown fuse in the A/C water pump circuit or the detection circuit can cause the code to be set. Always check the fuses first.
Conclusion
The B1968 A/C Water Pump Detection Circuit Failure can lead to discomfort and potential system damage. By systematically diagnosing the problem using the steps outlined above and addressing the underlying cause, you can restore your vehicle's A/C system to proper working order. Always consult a qualified technician if you are uncomfortable performing these repairs yourself.