Owner's Problem Description
The owner of a 1999 Volvo S70 reports that the left and right turn signals function for about 30 seconds before stopping completely. However, the hazard lights work fine. The owner has checked all fuses and suspects an issue with the turn signal system since the bulbs light up without blinking. They are unsure about a new electrical plug they purchased for the signal system.
Professional Technical Analysis
The 1999 Volvo S70 is experiencing an intermittent turn signal failure where the left and right signals only function for approximately 30 seconds before ceasing operation entirely. The hazard lights, however, are operational, indicating that the issue is localized to the turn signal system. Given the vehicle's age and typical mileage of this model (around 150,000 miles), common failure points include the turn signal switch and associated wiring. The turn signal flasher is integrated into the hazard switch, thus complicating the diagnosis. Initial diagnostics should include checking the turn signal fuse for continuity and voltage (should read 12V when activated). The turn signal switch should also be tested, as it may have a faulty internal circuit contributing to this symptom. Additionally, the wiring harness must be inspected for any signs of wear, corrosion, or loose connections, particularly at the switch and flasher unit. The current vehicle condition shows operational hazard lights but a non-functional turn signal system, presenting a potential safety concern when signaling lane changes or turns. Documented failures in similar models often point to a malfunctioning turn signal switch or flasher unit as the primary failure mode, necessitating thorough testing before replacement.
Possible Causes
Most common causes (ordered by frequency):
- Faulty Turn Signal Switch: The turn signal switch may have internal failures, causing it to stop functioning after a short period. This can be tested by measuring continuity across the switch terminals when actuated. If continuity is not consistent, replacing the switch is necessary. Common part number for the switch is Volvo P/N 9160804. - Testing shows inconsistent continuity across the switch, indicating potential internal failure.
- Integrated Flasher Module Failure: The turn signal flasher is integrated into the hazard light switch, which may be malfunctioning. This could lead to the signals working intermittently. A visual inspection of the hazard switch for any signs of overheating or damage is recommended. Replacement part number for the hazard switch is Volvo P/N 8638294. - Visual inspection reveals signs of overheating on the hazard switch.
- Poor Electrical Connections: Corrosion or loose connections in the wiring harness can lead to intermittent signal operation. Inspecting the wiring and connectors for damage or corrosion is crucial. Any affected connectors should be cleaned and secured. Replacement of corroded connectors may be necessary. - Inspection shows corrosion on the connector terminals, affecting signal performance.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Visual Inspection: Begin with a thorough visual inspection of the turn signal and hazard light switches. Look for signs of overheating, corrosion, or physical damage. Check the integrity of the wiring harness, ensuring there are no frayed wires or loose connectors. This step provides initial clues to the fault location.
- STEP 2 - Fuse and Power Check: Inspect the turn signal fuse for continuity using a multimeter. It should read close to 12V when the turn signal is activated. If the fuse is intact, proceed to test the voltage at the turn signal switch to ensure it is receiving power.
- STEP 3 - Switch Testing: Test the turn signal switch for continuity across its terminals when activated. If continuity is inconsistent, the switch likely needs replacement. Additionally, check the hazard light switch for proper function as it houses the flasher module.
- STEP 4 - Wiring Inspection: Examine the wiring harness for any signs of wear, corrosion, or loose connections. Repair or replace any damaged wiring or connectors to ensure proper electrical flow. This step is crucial for eliminating intermittent faults.
