🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Coolant temperature sender inaccurate gauge reading
💰 Estimated Repair Cost
$15 – $35 USD
Parts and labour estimate
🔧 Tools Required
Multimeter, hot water test
📋 Overview
The coolant temperature sender unit fails with age causing the gauge to read permanently high, low, or fluctuate erratically. An inaccurate gauge can mask genuine overheating.
🩺 Symptoms
- Temperature gauge reads abnormally high or low
- gauge fluctuates randomly
- gauge pins at maximum
🔍 Possible Causes
- Failed coolant temperature sender
- corroded sender connections
- failed gauge
🛠️ Diagnosis Steps
Disconnect sender. Gauge should drop to cold. Test sender resistance in hot water — should vary smoothly with temperature.
✅ Most Confirmed Fix
Replace coolant temperature sender. Clean connection.
83% of users confirm this fix worked (26 reports)
🏷️ Parts Needed
Coolant temperature sender for M115
🔗 Other Mercedes-Benz W115 Faults
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