Will a Car Fail MOT with the Temperature Gauge Not Working?
If your car’s temperature gauge is not working, you may wonder whether it could cause your car to fail its MOT test. The temperature gauge is part of your engine’s cooling system and helps monitor whether the engine is running too hot. If it stops working, you might not notice overheating before serious engine damage occurs. This guide explains what causes the temperature gauge to fail, how it affects your MOT result, and how much it costs to fix in the UK.
What the Temperature Gauge Does
The temperature gauge measures the engine coolant temperature and displays it on the dashboard. When the car starts cold, the needle stays low. As the engine warms up, the needle should move to the middle and remain steady.
If the gauge is not working, common reasons include:
- A faulty coolant temperature sensor
- Wiring or connector damage
- A broken gauge or instrument cluster fault
- A stuck thermostat
- Air trapped in the cooling system
A non-working gauge might not cause immediate issues, but it can hide serious overheating problems that lead to engine failure.
Will a Car Fail MOT with the Temperature Gauge Not Working?
In most cases, no, your car will not fail its MOT if the temperature gauge is not working.
The DVSA (Driver and Vehicle Standards Agency) MOT test does not include checking the function of the temperature gauge. The test focuses on safety, emissions, and mechanical condition, not on dashboard indicators like the temperature or fuel gauge.
However, your car could still fail the MOT if the fault causes related issues such as:
- Coolant leaks detected during inspection
- Overheating problems visible to the tester
- Warning lights like the engine management light staying on
- Excessive smoke caused by overheating
So, while the gauge itself is not checked, the cooling system faults behind it might lead to an MOT failure.
Common Causes and UK Repair Costs
| Cause | Description | Typical UK Repair Cost |
|---|---|---|
| Faulty Coolant Temperature Sensor | No temperature signal to gauge | £80 – £150 |
| Broken Gauge | Dashboard fault | £100 – £250 |
| Thermostat Stuck | Engine runs too cold or too hot | £120 – £250 |
| Wiring or Connector Fault | Damaged or corroded wires | £80 – £200 |
| Air in Cooling System | Causes false readings | £50 – £120 |
What Happens During the MOT
During the MOT, the tester checks that:
- The engine starts and runs correctly.
- There are no coolant leaks.
- The engine management light behaves correctly.
- There is no excessive smoke or signs of overheating.
Since the temperature gauge is not part of the MOT inspection checklist, the car will not fail simply because it does not show the engine temperature.
But if the car is overheating, leaking coolant, or showing warning lights related to the cooling system, it will fail.
How to Fix a Faulty Temperature Gauge Before MOT
- Check the coolant level and top up if it’s low.
- Inspect the wiring and connectors for corrosion or loose connections.
- Replace the coolant temperature sensor if it’s faulty.
- Bleed the cooling system to remove air pockets.
- Replace the thermostat if the car overheats or runs too cold.
A diagnostic check at a local garage usually costs £50 to £80, and repairs typically range between £80 and £250.
Is It Safe to Drive with the Temperature Gauge Not Working?
Driving with a broken temperature gauge is not recommended, especially for long trips.
Without a working gauge, you cannot tell if the engine is overheating. Prolonged overheating can lead to serious and expensive issues such as a blown head gasket or engine seizure.
If you notice steam from the bonnet, loss of power, or a hot smell, stop the car immediately and let it cool before checking the coolant level.
Preventing Temperature Gauge Problems
- Check coolant levels regularly.
- Have the cooling system serviced every two years.
- Use the correct coolant type recommended by the manufacturer.
- Replace the thermostat and sensor at the first sign of failure.
- Avoid driving with low coolant or leaks.
MOT and Pre-Purchase Inspection Advice
If you are buying a used car and the temperature gauge is not working, it could mean a minor electrical issue or a sign of past overheating.
A CAREXAMER pre-purchase inspection can reveal whether the fault is small or hiding a serious engine problem.
During an MOT, a faulty temperature gauge alone will not cause a failure, but any coolant leaks or overheating signs discovered during the test will.
Summary of Temperature Gauge Problems
| Problem | MOT Impact | Average UK Repair Cost |
|---|---|---|
| Faulty Temperature Sensor | No MOT fail | £80–£150 |
| Broken Gauge | No MOT fail | £100–£250 |
| Thermostat Stuck | Possible fail if overheating | £120–£250 |
| Wiring Fault | No MOT fail | £80–£200 |
| Coolant Leak | MOT fail | £100–£300 |
Conclusion
A car will not fail its MOT just because the temperature gauge is not working, as it is not a safety or emissions-related feature.
However, if the underlying problem causes the car to overheat, leak coolant, or trigger engine warning lights, the vehicle could fail.
Typical UK repair costs range from £80 for a temperature sensor replacement to about £250 for a thermostat or gauge repair.
To avoid overheating or MOT issues, fix the problem early. If you are unsure, a CAREXAMER inspection can identify cooling system faults before they become serious or expensive.
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