Air con gets less powerful as I'm driving

[Deleted member 66701]

This happened on my old Scorpio. The air con temp sensor had failed so the compressor would run continously and the heat exchanger would ice up and block airflow.

You can confirm this by popping out the pollen filters and looking at the exchanger when it happens. If the excganger is covered in white furry ice then it isn't de-icing properly. Another test is to see if airflow decreases without the air con enabled. If it doesn't, then it's got to be the exchanger icing up.

 

[Dr Who]

He's talking about actual air flow. Not cold air

You realise with A/C on the air flows through the evaporator, which if iced up, becomes a blockage.

OP: Try having the A/C refilled as it ices up faster with low gas, also make sure your windows etc are shut.

 

[Clarkey]

The ice theory makes good sense, hadn't thought of that.

 

[Entai]

You realise with A/C on the air flows through the evaporator, which if iced up, becomes a blockage.

OP: Try having the A/C refilled as it ices up faster with low gas, also make sure your windows etc are shut.

The evaporator can ice up if the system is overfilled with refridgerant as well

OP said he has just had the system re gassed.

Would take it back to get checked

 

[MrRockliffe]

Had Aircon on on the way back today, and strangely enough didn't encounter the same problem. Even had to turn the temp up a little as it got so chilly on number 1 setting.

I wonder if it's related to the temp outside

 

[Howard]

Can you still hear the fan going at high speed when the air flow drops?

 

[MrRockliffe]

Can you still hear the fan going at high speed when the air flow drops?

Yep

 

[MrRockliffe]

Update to this.

Over the weekend, took a trip to Loughborough and back to check out my place for when I'm back at university.

On the way there, aircon was fine, but I did stop off at services on the M1 after terrible traffic on the M25.

On the way back, however, around Heathrow, air stopped coming out again. This time, I turned off AC, and to begin with, air power was still low, just like before. After 15 seconds or so, though, airflow returned to high speed, and the loud fan sound disappeared.

Because of this, I am coming to the conclusion there's a blockage of ice/similar that forms over time somewhere in the system - turning off the AC and having normal air flow through it helps clear it more quickly. Does this sound plausible?

 

[Entai]

As I said before the evaporator can get iced up if the system has been over gassed, or as others have said under gassed.

All the symptoms you are seeing suggest this as a possible problem.

Go back and get the system standing pressures checked.