Drivable — worth looking into
The air conditioning will not come on
The button presses, the light comes on, but there is no cold air. Sometimes the compressor clutch does not click when switched on; sometimes the cold disappears only in heat or in traffic.
There is no danger, but the symptom will not go away by itself: it is the early stage of something that gets pricier.
What to look at in the live data
- Whether there is a compressor relay code: the circuit is checked before anyone talks about regassing.
- Idle speed when the button is pressed: a working compressor loads the engine and the revs rise slightly. Nothing changed means the compressor never engaged.
- Engine temperature: when overheating, the unit deliberately switches the air conditioning off, and that is not a fault.
Common causes, cheapest first
- The compressor fuse or relay — the cheapest and the commonest.
- Low refrigerant: the pressure switch deliberately prevents the compressor from running so as not to destroy it.
- A dirty condenser — there is cold air, but it fades in traffic.
- A pressure switch connector filled with water.
- The clutch or the compressor itself — expensive, and checked last.
Codes that show up with this
P0645A/C clutch relay — circuit malfunctionP0692Cooling fan relay — high signalP0693Cooling fan relay 2 — low signal
These parameters in the reference
Do it step by step
P0171 is not a random string but an address. We take it apart, sign by sign.Reading a fault code: the letter and four digits
A symptom is not a diagnosis. The same sign comes from a dozen different causes — the readings are what tell them apart, not the feeling.
How the app helps
CarScan shows exactly these readings live, remembers the highest and the lowest value of the trip, and puts them into a report you can hand to a mechanic.