Hope someone can help. Problem starting the car. The glow plugs are not heating up. I have checked the relay which works fine. I disconnected the temperature sensor and connected a voltmeter between a glow plug terminal and earth. When I switched on the ignition I had 12.5 volts for approx. 20 seconds and the glow plug light came on too. Voltage went to zero and glow plug light went off as they should. I checked the sensor terminals and had 0v on one and 5v on the other (I believe this is a reference voltage for the ECU which changes dependent upon the resistance of the sensor). This strikes me that the circuit is working normally without the sensor. When I connected the sensor back up the glow plug light  was on for about a second and the voltage was almost zero. I fitted a new sensor and exactly the same thing happened. I've tried finding a circuit diagram without success. Any ideas? I did think that there my be a short somewhere but my understanding is that the circuit appears to work fine and that the sensor simply alters the resistance in the circuit dependent upon the coolant temperature (cold = high resistance, hot = low resistance). Am I wrong?

Any help appreciated.

Obviously with glow plugs it's a diesel, but which diesel is it?

Mk1 Fabia 1.9tdi. Perhaps I should have also mentioned that I plugged in an OBD reader which showed no faults.

I can't help you from here unfortunately, sorry. I was just asking about engine types for the benefit of others who should be able to help.

What year is the car?

Car is a 2001 model.

I'll have a look at wiring info tomorrow and see if that suggests a diagnostic strategy. 

3 minutes ago, Wino said:

I'll have a look at wiring info tomorrow and see if that suggests a diagnostic strategy. 

Thanks for that. Trying to follow wires that go here, there and everywhere can be a nightmare - much easier if you know where to look. I wasn't sure if the ambient temperature sensor had any bearing on the problem but I can't see how.

1 minute ago, Rhylly said:

Thanks for that. Trying to follow wires that go here, there and everywhere can be a nightmare - much easier if you know where to look. I wasn't sure if the ambient temperature sensor had any bearing on the problem but I can't see how.

 

It doesn't, but there is a fuel temperature sensor which can also affect cold starting.

 

I wouldn't expect the glow plugs to be on very long in this mild weather and it wouldn't really affect starting, only exhaust smoke production. 

 

So I think you may be barking up the wrong tree.

You can download the wiring info yourself by going to this thread, clicking 'download ' then the fifth file option CFD 2000-2002.

https://www.briskoda.net/forums/files/file/76-mk1-fabia-workshop-manuals/

 

5 hours ago, Rhylly said:

Problem starting the car. The glow plugs are not heating up.

Do you get white smoke that smells of diesel fuel for a few seconds when it does fire?

25 minutes ago, KenONeill said:

Do you get white smoke that smells of diesel fuel for a few seconds when it does fire?

Not noticed any. It's always been a good little runner with clean exhaust and no smells.

9 hours ago, Rhylly said:

Not noticed any. It's always been a good little runner with clean exhaust and no smells.

Which suggests that your problem is not actually glow plugs then.