2016 Audi Q5 AC fan off and on, related to outside temp.

Question

I'm perplexed.  In the cool of the evening or early morning, the AC (or heat, for that matter, it's Canada) works fine.  But in the afternoon, when the cab has heated up, there is no response.  After driving 20 - 30 minutes on the highway, it suddenly kicks in and works fine.  I assume that can't be a fuse.  It seems like it's related to heat in the cabin, but it's not like, after 20 minutes on the highway, the cabin has cooled, but perhaps the airflow is cooling some sensor.  Or perhaps I'm completely wrong.  I'm not handy and afraid to end up with a huge bill as some mechanic goes on a fishing expedition.  If it were off and on sporadically, you would think of a bad switch, wire, or connection, but when it seems temperature related, I would think there is a sensor involved.

I would appreciate any of your wisdom.  I got none.  Thanks. !

Answer 1

It sounds like you're experiencing an issue with your Audi Q5's air conditioning system that seems to be temperature-related. Here are some insights into what might be causing this behavior and what steps you could consider taking.

Temperature Sensor or Thermistor
Your suspicion about a temperature-related sensor could be valid. Modern vehicles often have temperature sensors or thermistors that help regulate the operation of the HVAC (Heating, Ventilation, and Air Conditioning) system. If a sensor is malfunctioning, it could be causing the system to behave unexpectedly based on the temperature changes in the cabin. A malfunctioning sensor might not accurately detect the temperature and thus might not activate the AC as needed.

AC Compressor
The AC compressor is responsible for cooling the air before it enters the cabin. It's possible that there's an issue with the AC compressor or its related components. If there's a problem with the compressor clutch or the compressor itself, it might not engage properly when the cabin is warm, but could start working after a certain amount of driving when the system has cooled down a bit due to airflow.

Electrical Issue
While you mentioned you don't think it's a fuse, it's worth considering electrical components. There could be a loose connection, a faulty relay, or even a control module that's not functioning as expected. These issues might not show up as intermittent problems but could be influenced by temperature changes.

Expansion Valve
The expansion valve in the AC system regulates the flow of refrigerant and can be sensitive to temperature changes. A malfunctioning expansion valve could lead to inconsistent cooling behavior.

Given the complexity of modern automotive systems, it's challenging to pinpoint the exact cause without proper diagnostic tools.