Hi everyone,

I’m trying to understand why the PTC heater on my Ford Fiesta 1.4 TDCi 2011 (70 hp, manual A/C) doesn’t seem to work.

Here’s what I’ve checked so far:

• The thick power cables from the battery to the PTC heater are present.

• Fuses are OK.

• Relays are working.

• The PTC heater option is enabled in the PCM (confirmed with Forscan).

• And no DTC are present.

However, it never seems to activate. With the engine running and the engine cold, I still get no warm air from the vents until the engine coolant warms up, as if the PTC heater isn’t doing anything.

 

Does anyone know the exact conditions required for the PTC heater to activate on this model with manual A/C ?
Coolant temp thresholds, outside temp, blower position, A/C button, alternator load, etc.?

 

Any feedback or experience would really help.

Thanks!

On older models, the temp dial often needs to be turned to maximum heat for the PTC heater to kick in.

Not sure about the other criteria.

3 hours ago, TomsFocus said:

On older models, the temp dial often needs to be turned to maximum heat for the PTC heater to kick in.

Not sure about the other criteria.

Thanks for the info!
In my case, the temperature dial is already set to maximum heat, so that shouldn’t be the issue.

That’s why I’m trying to understand what the other activation conditions are (outside temperature, blower speed, alternator load, coolant temp, etc.)..

The 2011 Fiesta is a Mk7 in the UK.

Have you checked the State Of Charge (SOC) of your battery first thing in the morning ? If it is too low then the PTC may not operate.

7 minutes ago, unofix said:

The 2011 Fiesta is a Mk7 in the UK.

Have you checked the State Of Charge (SOC) of your battery first thing in the morning ? If it is too low then the PTC may not operate.

Yes by battery is brand new. I've changed it last week. It's a 60Ah

From memory and the figures may be one or two degrees out, it should work when the outside Temperature is less than 9 degrees and the Coolant is less than 60 degrees and it switches off when either of these temperatures exceed these figures. 

3 hours ago, Tizer said:

From memory and the figures may be one or two degrees out, it should work when the outside Temperature is less than 9 degrees and the Coolant is less than 60 degrees and it switches off when either of these temperatures exceed these figures. 

This morning the outside temperature was below 0°C and the cooling way below 60°C... However it did not activate either

Edited November 27, 2025Nov 27 by eyzinox
misclick

3 hours ago, Tizer said:

From memory and the figures may be one or two degrees out, it should work when the outside Temperature is less than 9 degrees and the Coolant is less than 60 degrees and it switches off when either of these temperatures exceed these figures. 

This morning the outside temperature wa

1 minute ago, eyzinox said:

This morning the outside temperature was below 0°C and the cooling way below 60°C... However it did not activate either

Is the PTC heater also enabled in both the GEM and the cluster on Forscan?  It takes inputs from more than just the PCM.

13 minutes ago, TomsFocus said:

Is the PTC heater also enabled in both the GEM and the cluster on Forscan?  It takes inputs from more than just the PCM.

I didn't check. But I remember that I don't have GEM personnalisation on Forscan. And the cluster is IPC right ?

1 hour ago, eyzinox said:

I didn't check. But I remember that I don't have GEM personnalisation on Forscan. And the cluster is IPC right ?

Yes, IPC or HEC, depending on model.

Another thought, have you tested the heater itself?   After 15 years maybe it is just broken?

56 minutes ago, TomsFocus said:

Yes, IPC or HEC, depending on model.

Another thought, have you tested the heater itself?   After 15 years maybe it is just broken?

No, I haven’t tested the heater itself, as I haven’t been able to locate it. According to the Ford catalog, the heater should be located next to the cabin filter.

13 minutes ago, eyzinox said:

No, I haven’t tested the heater itself, as I haven’t been able to locate it. According to the Ford catalog, the heater should be located next to the cabin filter.

Ah ok, I thought you'd checked the thick cables to it?  These didn't all get a PTC heater fitted.  It is possible that your car just doesn't have one if you can't see it.  Do you mind saying which country you're in?

It may also be possible for us to confirm whether the heater was fitted if you can post the VIN number.

On 11/27/2025 at 2:35 PM, TomsFocus said:

Ah ok, I thought you'd checked the thick cables to it?  These didn't all get a PTC heater fitted.  It is possible that your car just doesn't have one if you can't see it.  Do you mind saying which country you're in?

It may also be possible for us to confirm whether the heater was fitted if you can post the VIN number.

But then why do I have the two relays (R1 and R2) for the PTC heater in the secondary fuse box under the headlight?
I also have the thick power cables coming from the battery with the 80A fuses.

I just can’t find the PTC heater itself. I looked behind the cabin air filter and behind the dashboard on the driver’s side.
What is it supposed to look like exactly?

For info, my car is from France.

1 hour ago, eyzinox said:

For info, my car is from France.

Can you post a quick photo of your car please ?

There is something I just need to confirm before making any comment.

This eBay ad shows the heater well.  It's a UK ad so I hope you can open it.

https://ebay.us/m/KTpW73

 

22 minutes ago, unofix said:

Can you post a quick photo of your car please ?

There is something I just need to confirm before making any comment.

Yes, here it is! 

23 minutes ago, TomsFocus said:

This eBay ad shows the heater well.  It's a UK ad so I hope you can open it.

https://ebay.us/m/KTpW73

 

Ok, I didn’t see this part last time. But I did see a plastic cover… so I presume that I don’t have a PTC heater installed.

But it’s strange, because I do have the wiring at the battery and the two relays.
Is it possible to retrofit the PTC heater easily?

7 minutes ago, eyzinox said:

Ok, I didn’t see this part last time. But I did see a plastic cover… so I presume that I don’t have a PTC heater installed.

But it’s strange, because I do have the wiring at the battery and the two relays.
Is it possible to retrofit the PTC heater easily?

Yes it's easy to retrofit the heater.  Will obviously need to work out whether you have the wiring and plug inside the car for it first.  Will also need to enable it using Forscan.

3 minutes ago, TomsFocus said:

Yes it's easy to retrofit the heater.  Will obviously need to work out whether you have the wiring and plug inside the car for it first.  Will also need to enable it using Forscan.

Great, thanks for the info!
Tomorrow I’ll check whether the connector is inside the car. From the pictures I’ve seen on eBay, it should be fairly easy to spot. I’ll update the thread once I’ve confirmed it.

When I was looking around the cabin filter area last time, I did find a 2-pin connector clipped to a wiring loom close to the ventilation control module.
Could that possibly be the one for the PTC heater?

19 minutes ago, eyzinox said:

Yes, here it is! 

Thank you, but unfortunately I can't see the picture. It's not your fault it's an ongoing problem that I have with the FOC site ever since they did a software upgrade.

@Steve The problem is still happening. I'm using my mobile with wifi turned off and connected by 5G.

I also get the same problem on my laptop.

 

Well the good news is the photo has at last become available 👍

So having checked the schematics, I can see it is fitted with one Booster Heater unit which has two heating elements, which is why it has two power relays controlling it.

Below are some pages of how the heater is wired and controlled.

10 hours ago, unofix said:

the photo has at last become available

Interesting. I still can't see it. Perhaps its is working since @Steve whitelisted your IP address.