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Climate control blows hot air only

David M

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Can anyone help, I've a 2004 S-type 2.5 petrol. Heating/cooling has been working well but when I tried to adjust to cooling for the first this year, I only got hot air. I have changed the heater control valve but still no cold air. What should be the likely next step? I thank you for any suggestions. 

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Hi,My air con was doing opposite, blowing cold,

It was rattling and smelt of rubber from the engine bay, that was the pump.

I found the following, may be it could help.

It says to check the following if blowing hot air only.



A car A/C blowing hot air is often the result of a refrigerant leak. Refrigerant is a liquid that circulates through your car's A/C system, expanding and contracting as it removes heat and humidity from the cabin. None of the other A/C components will function correctly without proper refrigerant levels.

A leak can happen because of an old hose as well as a rusted or punctured evaporator. But don't expect to easily spot a refrigerant leak. You probably won't notice a puddle of liquid in or under your car. That's because unlike motor oil and other vital car fluids, antifreeze evaporates when exposed to the atmosphere. Sometimes, you'll get lucky and notice an oily residue at the exact location of the leak.

To definitively identify a refrigerant leak, one of our expert technicians needs to inject dye into the system to trace it. Once they identify the source of the leak, they repair and recharge your car A/C so it can blow fresh, cold air once again.


When your A/C system pulls the heat and humidity out of your cabin, the refrigerant absorbs them. In turn, the condenser's function is to keep the refrigerant cool so the cycle can continue. If the condenser isn't doing its job, the process breaks down. That's when you get slapped in the face by a blast of hot air.

The condenser is at the front of the car, between the grate and the radiator. It utilizes air flowing through the grate to assist in cooling. If the condenser is blocked or clogged by road debris, air won't reach it, preventing the refrigerant from cooling correctly.

If you have a faulty condenser, you may be able to see the problem by looking through the grate. Also, consider whether your car A/C problems started after a fender bender or bumper bump, in which case your condenser might have broken on impact.


The compressor is the heart of your car's A/C. It's responsible for circulating the refrigerant through the system. If this part isn't working correctly, the antifreeze won't be able to reach the condenser for cooling.

Compressor issues tend to pop up after long periods of inactivity, such as long winters when A/C isn't necessary. However, to prevent this from happening, many newer vehicles keep the condenser active year-round by activating it under the defrost setting.


If all the A/C components are in working order, your car may be blowing hot air because of an electrical issue. A frayed wire or a blown fuse can prevent an otherwise healthy A/C from functioning. Diagnosing and correcting an electrical problem begins with performing a complete visual inspection of your car's fuse box and wiring.



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  • 2 weeks later...

There is a very comprehensive fault finding procedure on the US Jag Forum, Follow it and you will have no doubts about the cause. Well almost! Only 2 faults remaining are Compressor and or Condenser, Hope for the first because the 2nd means you scrap the car unless you are a real nutter!

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