“AC just needs gas recharge”—₹1,500 becomes ₹35,000 when you discover the compressor is seized.
Climate control isn’t luxury—it’s essential for visibility (defog) and comfort. When HVAC fails, symptoms are obvious (no cooling) or subtle (weak airflow, bad smell). Sellers do temporary fixes: gas recharge masks compressor failure (₹25,000-40,000), cleaning hides evaporator fungus (₹8,000-15,000), or they simply don’t test heater in summer. You discover the expensive truth after purchase.
The trap: Seller recharged AC gas before showing car. Works for 2 weeks, then stops—compressor leaking, needs replacement.
What you’ll learn:
- AC system testing (cooling performance, airflow)
- Compressor health (sound, engagement)
- Heater operation (blend door, coolant flow)
- Common failures and costs (₹3,000-45,000)
- When bad smell means expensive evaporator cleaning
Section 1: AC Cooling Performance Test
Test procedure:
1. Start with warm car:
- Park in sun for 10 minutes (if possible)
- Interior temperature elevated
2. Start engine, set AC to max:
- Temperature: Lowest setting
- Fan speed: Maximum
- Recirculation: ON
- Vents: Dash vents (center)
3. Measure cooling time:
- Good system: Noticeable cooling within 2-3 minutes
- Problem: Little/no cooling after 5 minutes
4. Temperature measurement (if thermometer available):
- Vent temperature should reach 5-7°C within 5-10 minutes
- Problem: >15°C = weak cooling
5. Compressor engagement:
- Listen for click when AC turned on (compressor engaging)
- Problem: No click = compressor not engaging (electrical issue or compressor failure)
Section 2: Common AC Failures
Failure 1: Low refrigerant (gas leak)
Symptoms:
- Cooling weak or intermittent
- Works initially, stops after 10-20 minutes
Cause: Leak in system (condenser, evaporator, lines)
Temporary fix: Gas recharge (₹1,500-3,000)
- Lasts 2-6 months before leak empties system again
Proper fix:
- Find and repair leak: ₹3,000-15,000 (depending on component)
- Evaporator replacement: ₹15,000-30,000 (requires dashboard removal)
Failure 2: Compressor seizure
Symptoms:
- No cooling
- Loud grinding noise when AC turned on
- Belt may squeal
Cause: Lack of lubrication, old age, contamination
Repair: Compressor replacement
- Cost: ₹25,000-45,000 (parts + labor)
- Also requires: System flush (₹5,000-10,000)
Failure 3: Blocked condenser
Symptoms:
- Weak cooling, especially at idle
- Improves slightly when driving (airflow increases)
Cause: Condenser fins blocked (dust, debris, insects)
Fix: Condenser cleaning (₹1,000-2,500)
- If damaged/leaking: Replace (₹8,000-18,000)
Failure 4: Blower motor failure
Symptoms:
- No airflow from vents
- Or: Airflow only at maximum speed (resistor failure)
Cause: Motor worn out, resistor burnt
Repair:
- Blower motor: ₹3,000-8,000
- Resistor: ₹1,500-4,000
Section 3: Heater Testing
Often neglected (especially in summer):
Test procedure:
1. Set climate control:
- Temperature: Maximum heat
- Fan: Medium speed
- AC: OFF
2. Wait 3-5 minutes (engine must be warm)
3. Check vent temperature:
- Should blow HOT air (60-70°C, too hot to hold hand in front)
Problem indicators:
1. No heat:
- Cause: Blend door stuck (₹8,000-15,000 to repair)
- Or: Heater core clogged (₹10,000-20,000 to replace)
2. Coolant smell:
- Sweet smell from vents
- Cause: Heater core leaking (₹10,000-20,000)
- Also: Windshield fogs up (oily film)
3. Lukewarm air only:
- Cause: Low coolant, thermostat stuck open (₹2,000-5,000)
Section 4: Airflow and Vent Testing
Test all vent modes:
1. Dashboard vents (face):
- Strong airflow should come from center + side vents
2. Floor vents:
- Air directed to footwells
3. Windshield defrost:
- Air directed to windshield base
- Critical for: Defogging in monsoon
4. Mix mode:
- Air split between dash and floor
Problem indicators:
1. Weak airflow:
- Cause: Cabin air filter clogged (₹500-1,500 to replace)
- Or: Blower motor weak
2. Air comes from wrong vents:
- Cause: Blend door actuator failure (₹5,000-12,000)
3. Whistling/hissing:
- Cause: Leak in ductwork
Section 5: Smell and Air Quality
Common smells:
1. Musty/mildew smell:
- Cause: Fungus/bacteria on evaporator
- Fix: Evaporator cleaning (₹2,000-5,000)
- Prevention: Run AC on max cold for 5 min, then turn off AC but keep fan on max for 2 min (dries evaporator)
2. Sweet smell:
- Cause: Coolant leak (heater core)
- Serious: Coolant fumes toxic
- Fix: Heater core replacement (₹10,000-20,000)
3. Burning smell:
- Cause: Electrical issue (blower motor, resistor)
- Or: Debris burning on heater core
- Action: Investigate immediately
Section 6: Climate Control Features
Manual vs automatic climate control:
Manual:
- You control temperature, fan speed, mode
- Simpler, fewer failure points
Automatic:
- Set desired temperature, system maintains it
- Sensors, actuators = more complexity
- Failure: Sensor/actuator issues (₹3,000-15,000)
Dual-zone climate control:
- Driver and passenger set different temperatures
- If one zone doesn’t work: Blend door actuator (₹5,000-12,000)
Section 7: Real Case – The Temporary Gas Fix
2020 Maruti Brezza ZXI, 50,000 km, asking ₹10,20,000
Test drive (March, warm weather):
- AC worked well, cold air
- Buyer satisfied
One month after purchase (April, hot):
- AC stopped cooling
- Took to mechanic
Mechanic’s finding:
- System empty (no gas)
- Evaporator leak (common Brezza issue in this batch)
Leak detection:
- UV dye test confirmed evaporator leaking
Repair quote:
- Evaporator replacement: ₹22,000
- Requires: Dashboard removal (8-10 hours labor)
Buyer contacted seller:
- Seller: “AC was working when you bought it”
- Buyer: “Did you recharge gas before sale?”
- Seller (reluctantly): “Yes, few days before”
Seller knew about leak, temporarily fixed to sell
Outcome: Buyer paid ₹22,000 (no recourse, should have tested thoroughly or demanded warranty)
Lesson: Test AC performance, ask “when was AC last serviced/recharged?”
Conclusion: Climate Control is Critical Comfort
HVAC failures are expensive. Test thoroughly, every function, before buying.
Your protocol:
AC test (10 minutes):
- Max cold, max fan
- Check cooling time, vent temperature
- Listen for compressor engagement
Heater test (5 minutes):
- Max heat
- Verify hot air output
- Check for coolant smell
Airflow test (5 minutes):
- Test all vent modes
- Check airflow strength
Smell check (immediate):
- Musty, sweet, burning = problems
Decision framework:
- All functions work, no smells: Proceed
- Weak cooling (may need gas): Negotiate ₹3,000-5,000 discount
- Musty smell: Negotiate ₹3,000-5,000 (cleaning)
- Compressor noise or no cooling: Negotiate ₹30,000-50,000 OR walk away
- Sweet smell (coolant leak): Negotiate ₹12,000-20,000 OR walk away
Comfort isn’t optional in Indian summers. Make sure the AC works—properly, not temporarily.
Key Takeaways
✓ Recent gas recharge = likely leak (ask seller when last serviced)
✓ Compressor failure = ₹25-45K (grinding noise, no cooling)
✓ Evaporator leak = ₹15-30K (requires dashboard removal)
✓ Musty smell = evaporator fungus (₹2-5K cleaning)
✓ Sweet smell = heater core leak (₹10-20K, toxic fumes)
✓ Test heater even in summer (blend door issues only visible when testing)
✓ Cabin filter clogged = weak airflow (₹500-1,500, easy fix)
Checklist References
- interior#38: AC cooling performance
- interior#53: Heater operation
- interior#70: Climate control function (all modes)
- interior#39: Unusual smells from vents
Related Reading:
Next Steps
Professional HVAC diagnostics → Pressure test, leak detection, temperature measurement
Check service history for AC repairs → Recent recharges indicate leaks
AC recharge is a band-aid. Find the wound before you buy.