Climate control and air-conditioning problems in the Volvo S90 call for a targeted diagnosis. Fluctuating temperatures are not always caused by too little refrigerant. A fault in compressor control, a blocked condensate drain or restricted airflow can produce the same effect. Also take a look at the known problems with the Volvo S90 if you notice multiple complaints about the car. With the right checks, you can avoid replacing parts unnecessarily. So read on to find out what to look at first.
Causes of climate control problems in the Volvo S90
If the climate control is playing up, the temperature can change without any obvious reason. One moment cold air comes from the vents. Shortly afterwards, the system suddenly blows lukewarm or warm air. Some drivers even notice the heater working at full blast while it is warm outside. That kind of complaint points more to a control issue than to a completely failed air-conditioning system.
The Volvo S90 uses sensors and electronic control to keep the set temperature steady. The system controls the compressor, fan and air flaps, among other things. A fault anywhere in that chain can cause the measured cabin temperature to differ from the actual temperature.
Common causes of a malfunctioning climate control system include:
- an electrical or control fault in the climate system;
- a compressor control valve that does not respond properly;
- a dirty cabin filter that restricts airflow;
- blocked air ducts or a problem with the blower fan;
- too little refrigerant due to a leak;
- a dirty condenser that does not dissipate heat as well;
- a blocked condensate drain in the climate unit.
Do not start by topping up the refrigerant. The system may still contain enough refrigerant. Even so, the air-conditioning can cool poorly because of problems with compressor control or air distribution. So have the fault codes read first. Also check the sensors, flaps and blower fan are working properly.
Fluctuating cold and warm air in the Volvo S90
Fluctuating cold and warm air in the Volvo S90 can occur in various situations. Sometimes the temperature on one side of the cabin remains stable. The other side then alternates between cold and warm. In other cases, the temperature changes at all vents at once. That difference helps the workshop narrow down the problem further.
If one climate zone behaves differently, a problem with an air flap or its control is the obvious suspect. If the air changes everywhere at once, the central control unit should also be investigated. A compressor that is being controlled irregularly may stop cooling temporarily. Later, the system sometimes seems to work normally again.
Check the complaint in different conditions
A short test on the driveway does not always tell you enough. Some problems only occur in warm weather, high humidity or after prolonged use on the coldest setting. So test the climate control both while stationary and while driving.
- Start the car and set both climate zones to the same temperature.
- Check whether roughly the same amount of air comes from all vents.
- Switch on the air-conditioning and note how quickly the air cools.
- Change the temperature and check whether the system responds smoothly.
- Then take a longer drive and note when the temperature starts to fluctuate.
During this check, also listen for noises from the dashboard. A flap that does not move properly can cause audible clicking or repeated movement. If the blower fan does not work on every setting, the blower control also deserves attention.
Air-conditioning problems in the Volvo S90 T6 and T8 after intensive use
In T6 and T8 models, air-conditioning problems can become particularly noticeable after intensive use of the climate control. The system cools well at first, but later loses cooling capacity or starts to work unevenly. Warm weather, high humidity and prolonged cooling at full power can make an existing problem more obvious.
This does not automatically mean the compressor needs replacing. The compressor control valve determines how much cooling output is delivered. This valve can respond incorrectly or irregularly. If cooling is poor and airflow is low, a technical diagnosis is therefore needed. The workshop will check the control valve, condensate drain and system pressure, among other things.
The condenser also deserves checking. This component sits at the front of the car and removes heat from the refrigerant. Dirt or a blockage can limit heat dissipation. As a result, the air-conditioning performs less well under heavy load. Establish the cause first before replacing any parts.
Repairing a faulty air-conditioning system in the Volvo S90 D5
Repairing a faulty air-conditioning system in the Volvo S90 D5 starts with measurements, not with ordering parts. An air-conditioning service that only adds refrigerant can have a temporary effect if there is a leak. Without a leak test, the problem will return.
A careful diagnosis usually follows this order:
- Read fault codes with equipment suitable for Volvo.
- Test the blower fan, airflow and temperature at the vents.
- Check the cabin filter, air ducts and condensate drain.
- Measure the pressure in the refrigerant circuit.
- Check the lines, connections, condenser and compressor for leaks.
- Assess the compressor control valve and electrical control.
After these checks, it becomes clear which repair is needed. That may be a repair, cleaning or replacement. If pressure is too low, a leak test is the first step. If the pressure is correct and cooling is irregular, investigation into the control system is the more likely route.
‘ Water ingress could have affected airbag operation. ’
Moisture and odour point to drainage problems
A stale smell, misted-up windows or dampness under the floor mats may point to a blocked drain in the climate unit. Condensation forms during cooling. That water should leave through a drain under the car.
If the drain becomes blocked, moisture can remain in or around the climate unit. This causes odour and can eventually lead to water in the cabin. For certain model years, there has been a safety-related action concerning a potentially leaking air-conditioning drain. Water ingress could have affected airbag operation.
So check which relevant service actions have already been carried out on the car. A Volvo workshop can verify this using the vehicle identification number. If there is visible water in the cabin, do not delay investigation. Moisture can also damage electrical connections.
This is how to avoid a wrong air-conditioning diagnosis
Note in advance when the fault occurs and which settings are active. Mention whether the complaint appears only when stationary, during a long journey or after maximum cooling. Also state whether both sides of the cabin react the same. This information helps a mechanic reproduce the fault in a targeted way.
During a test drive in a used S90, check whether the air-conditioning starts cooling straight away. Also make sure the temperature remains stable over time. Look for signs of damp on the floor mats and watch out for a stale smell. Also ask about previous work on the compressor, condenser, drain and refrigerant circuit.
Climate control problems in the Volvo S90 are often manageable. To do that, check the airflow, pressure, drain and electronic control together. On the Carnews website, you will find more information about Volvo problems, servicing, buying checks and other technical topics. Discover the articles on Carnews and prepare better for diagnosis, repair or buying a used car.
Frequently asked questions
Common faults include weak or fluctuating cooling, poor airflow and a compressor that does not switch on or does so irregularly. These are often caused by a low refrigerant level, a leak, a dirty condenser or a faulty compressor control valve. Blocked condensate drains, stale smells, moisture in the cabin and problems with the cabin filter or air ducts also occur. Electrical or control faults in the climate system can also arise.
Set the climate control to the lowest temperature and maximum fan speed, then check whether the air quickly becomes cold, both when stationary and while driving. Test all fan settings; weak airflow may point to a blocked cabin filter, a faulty blower or blocked air ducts. Listen for the compressor switching on and look out for fluctuating cooling, a stale smell, misted-up windows or water in the footwell. If cooling remains inadequate, have the system pressure, leaks, condensate drain and compressor control checked with Volvo-specific equipment.
Replace the cabin filter according to the service schedule and keep the condenser, vents and air ducts clear of dirt. Use the air-conditioning regularly, even in winter, and watch for reduced cooling, weak airflow, stale smells or moisture in the footwell. If you notice any symptoms, have the condensate drain, compressor control, system pressure and any leaks checked before topping up the refrigerant. Also check whether all Volvo service and recall actions for the climate system have been carried out.
