Hello all,

I'm having some trouble with my Fiesta TDCI 1.6 MK6 2008.

I had the glow plugs changed just under two years ago (apparently all of them). The car continued running fine up until two weeks ago.

I noticed the heating was bad. It would takes ages to heat up and when I had the heater on the temperature would go down if stationary. Although it did remain at 90 when driving.

I'd say the thermostat was bad for 2 years or so, even before the glow plugs were changed. I decided to get the thermostat fixed. Two days later, check engine light comes on and it's P0380 - the glow plugs are gone again. Seems odd that they only lasted two years unless the garage didn't replace all of them.

The garage told me they were now seized and they didn't want to risk taking them out. I've finally found somebody who thinks they can do it but it wasn't easy.

Even with the new thermostat, the heating is still not warm. Could this be caused by the bad glow plugs?

Is there anything else that I should look at replacing?

The coolant temperature isn't related to the glowplugs.

On the 16v 1.6 TDCi, due to the way the plugs are wired, when one plug fails, the rest get stuck on permanently until they all burn out.  So it's unfortunate for them to have gone so soon, but if just one was left, that could easily have wrecked the new 3 if it failed recently.

On 3/1/2023 at 7:56 PM, TomsFocus said:

The coolant temperature isn't related to the glowplugs.

On the 16v 1.6 TDCi, due to the way the plugs are wired, when one plug fails, the rest get stuck on permanently until they all burn out.  So it's unfortunate for them to have gone so soon, but if just one was left, that could easily have wrecked the new 3 if it failed recently.

Hi Tom,

I wanted to ask you a question.

I've managed to pull three out easily, the last one snapped.

If I just unplugged the last one and then installed three new ones, would they be stuck on permanently or no?

Thanks in advance.

8 minutes ago, JordyC123 said:

Hi Tom,

I wanted to ask you a question.

I've managed to pull three out easily, the last one snapped.

If I just unplugged the last one and then installed three new ones, would they be stuck on permanently or no?

Thanks in advance.

Hmm, electrics are more @unofix area.  All I can remember is that the lack of resistance in one plug stops the PCM switching off the others.  I'm not sure if an open circuit on one plug would have the same effect or not.  Leaving them all unplugged until that one is replaced would be safer.

43 minutes ago, TomsFocus said:

Hmm, electrics are more @unofix area.  All I can remember is that the lack of resistance in one plug stops the PCM switching off the others.  I'm not sure if an open circuit on one plug would have the same effect or not.  Leaving them all unplugged until that one is replaced would be safer.

Thank you, really appreciate your help.

Unfortunately I don't have the schematics for the 2008 Mk6.

Looking at the configuration of the Glow Plug control of the 2012 Mk7 it would appear that leaving one glow plug disconnected will not cause a problem for the other 3. The PCM does monitor the operation of the glow plugs and will know that there is a failure of one glow plug (not connected) and will generate a DTC, but that is very unlikely to turn on the EML.

I've attached the wiring schematic of the glow plugs of a 2012 Mk7 which I expect will be very similar to that of the Mk6. You will see that each glow plug is powered individually from the GPM but that the monitor signal to the PCM is common to all of them.

The 2012 Mk7 uses the later 8v engine.  I wouldn't rely on the wiring being the same as the older 16v.

On 3/19/2023 at 11:37 AM, unofix said:

Unfortunately I don't have the schematics for the 2008 Mk6.

Looking at the configuration of the Glow Plug control of the 2012 Mk7 it would appear that leaving one glow plug disconnected will not cause a problem for the other 3. The PCM does monitor the operation of the glow plugs and will know that there is a failure of one glow plug (not connected) and will generate a DTC, but that is very unlikely to turn on the EML.

I've attached the wiring schematic of the glow plugs of a 2012 Mk7 which I expect will be very similar to that of the Mk6. You will see that each glow plug is powered individually from the GPM but that the monitor signal to the PCM is common to all of them.

Thank you for the very comprehensive information!