C5 II Glow plug relay test

Unread post by **Mihael_M** » 12 Dec 2025, 18:30

It is the temperature sensor located on the thermostat. But there are other sensors that measure the temperature, but I don't know where they are all.

sydo · Unread post by **sydo** » 17 Dec 2025, 06:14

Mihael_M wrote: 12 Dec 2025, 18:30 It is the temperature sensor located on the thermostat. But there are other sensors that measure the temperature, but I don't know where they are all.

When does the glow plug warning light come on? Does it come on in case of a malfunction or when the glow plug is engaged? When I disconnect the temperature sensor socket on the thermostat and turn on the ignition, the glow plug warning light comes on and goes off after about 10-15 seconds. The heating warning light never comes on when the temperature sensor socket is connected.

Unread post by **Mihael_M** » 18 Dec 2025, 08:22

Glow plug warning light only appears when the active heaters are in the preheating phase. The ignition switch is at the 2nd position (ignition on). Wait until the warning lamp has switched off before starting. The duration for which the warning lamp is on is determined by the climatic condition. The temperature displayed on the dashboard is the water temperature and probably has nothing to do with the heaters. There is a fuel temperature sensor and it has to do with the heaters. That sensor can be checked with the diagbox.

sydo · Unread post by **sydo** » 18 Dec 2025, 17:20

Mihael_M wrote: 18 Dec 2025, 08:22 Glow plug warning light only appears when the active heaters are in the preheating phase. The ignition switch is at the 2nd position (ignition on). Wait until the warning lamp has switched off before starting. The duration for which the warning lamp is on is determined by the climatic condition. The temperature displayed on the dashboard is the water temperature and probably has nothing to do with the heaters. There is a fuel temperature sensor and it has to do with the heaters. That sensor can be checked with the diagbox.

Is the fuel temperature sensor you're referring to the one located on the fuel rail?

Unread post by **Mihael_M** » 18 Dec 2025, 18:27

I don't know the exact location. It looks like this.
https://www.autodoc.co.uk/ridex/1523781 ... ure-sensor
The fuel temperature sensor is incorporated in the low pressure fuel pipe and not in the high-pressure rail.
It should not be confused with the high pressure sensor in the rail since it is similar.

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C5 II Glow plug relay test

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