Ford Mondeo 1999 with air con - Air distribution switch is to screen only

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Sat 20 Sep 2014 12:03
Ford Mondeo 1999 with air con - Air distribution switch is to screen only - Cicero

The air distribution switch will only send the air to the windscreen vents regardless of its position.

I know it is a vacuum operated system on this car and I have looked up previous posts on this subject. However, I still do not fully understand either how it works or how to diagnose the problem.

Can anybody help, please?

Thanks.

Chris

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Sat 20 Sep 2014 14:50
Ford Mondeo 1999 with air con - Air distribution switch is to screen only - elekie&a/c doctor

This is a very simple system,however if there is a vacuum loss,then the system defaults to windscreen only.Firstly take a look at the side of the heater box ,from drivers footwell.You should see a plastic vacuum tank clipped to the side of the heater.On the bottom of this is a black plastic pipe.Pull this off ,and with engine running ,there should be vacuum at this point.If there is ,then you need to pull out the heater control panel to check for vacuum here.If there is no vac present at the tank ,then it is posible the take off pipe under the engine inlet manifold has come adrift/broken.

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Sat 20 Sep 2014 19:55
Ford Mondeo 1999 with air con - Air distribution switch is to screen only - Cicero

Thanks for your prompt help.

I'll have a look tomorrow, weather permitting. Do I have to take off the trim to the left of the clutch pedal to see the heater box or should I be able to see it with enough contortions?

Chris

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Sat 20 Sep 2014 22:01
Ford Mondeo 1999 with air con - Air distribution switch is to screen only - elekie&a/c doctor

The vac tank and pipe should be visible without removing any trim. Access to the heater control panel is a bit more involved.

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Mon 22 Sep 2014 13:05
Ford Mondeo 1999 with air con - Air distribution switch is to screen only - Cicero

With the engine running, I disconnected the pipe from the inlet manifold at the junction by the bulkhead in the engine compartment and I had vacuum.

I then looked for the pipes near the heater box by the clutch pedal and found 2. One seemed to have a one-way valve, similar to that on a brake servo system, which I couldn't get apart. I disconnected the other one and there was a hiss indicating that I had disturbed a vacuum. Then with the engine running, I found vacuum on the pipe although I had the impression that it was possibly not as strong as that in the engine compartment - not sure really.

Do you have any suggestions for the next stage, please?

Thanks, I am very grateful for your help, so far.

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Mon 22 Sep 2014 13:35
Ford Mondeo 1999 with air con - Air distribution switch is to screen only - elekie&a/c doctor

You will need to access the back of the heater control panel to see if there is any vacuum here.

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Mon 22 Sep 2014 20:34
Ford Mondeo 1999 with air con - Air distribution switch is to screen only - Cicero

I think removing the heater control panel is probably beyond my capabilities.

Meanwhile, I have removed the glovebox and found the actuator just behind and to the RHS of the glovebox. A yellow pipe goes into the end of the canister and there is no vacuum at that point, regardless of the position of the air flow direction switch.

A red pipe joins the waist of the canister and there is a very slight vacuum there. By pushing the actuator rod into the canister a little way, by hand, I can get air flow from the footwell vents.

Does all this mean anything?

Thanks

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Mon 22 Sep 2014 21:43
Ford Mondeo 1999 with air con - Air distribution switch is to screen only - elekie&a/c doctor

Yes,it means there is not enough vacuum to pull on the actutors.The only way forward here is to access the heater control panel,which is not as difficult as it looks.Once the radio is out,there are a few screws and the fascia panel unclips to access the heater control .There are no cable controls to deal with as the system is vacuum and electric operation.

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Wed 24 Sep 2014 14:11
Ford Mondeo 1999 with air con - Air distribution switch is to screen only - Cicero

It is going to be another 10 days or so before I can get back to solving this.

Thanks for your help.

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