Those old dog days of summer are upon us, so it's a great time to revisit some practical air conditioner test tips.
These items may seem very basic — but some service personnel some-times overlook them.
Many readers have seen vehicles roll into their tire dealerships or service shops with a common complaint: The air conditioner just isn't working up to par. Although it blows some cold air, it just doesn't seem to cool as well as it normally does, according to the sweltering customer.
At many service facilities, the boss orders a technician to check the air conditioner's refrigerant pressures first. But what happens when the tech finds that the pressures are normal?
First and foremost, be sure techs are checking the following fundamentals before proceeding with the diagnosis. On the one hand, measuring and recording refrigerant pressures is a worthwhile step on any inadequate cooling complaint. That said, why spend more time than necessary diagnosing the root cause?
For instance, be sure that the car owner has kept all the windows up when the air conditioner's running. (Indeed, you have to witness this one to believe it!)
Also, check the air outlets on the dashboard. Sometimes another driver (spouse, children) have closed one of the vents because he or she thought the air flow was too cold. When the regular driver gets into the car again, he or she doesn't realize that someone else closed that vent — hence, the feeling of inadequate cooling.
Other times, the recirculation control is the root of all cabin cooling evils. That is, someone switches the dashboard control from recirculate (RECIRC) to fresh air. Unwittingly, the driver who does this is challenging the air conditioner to cool and dry incoming hot, humid air as well as the air already inside the passenger compartment.
Mind you, some air conditioners have enough cooling capacity to meet this challenge, but typically, switching the dash control from fresh air to RECIRC makes an immediate and noticeable improvement in interior cooling.
Lastly, watch out for a heater control valve that's stuck open. When the driver turns the dashboard control toward the maximum-cooling position, the system should close the heater control valve. This shuts off coolant flow through the heater core so a hot heater core doesn't compete with the air conditioner.
This failure — which may fool a careless or inexperienced tech — happens because the refrigerant pressures measure normal but the driver says the system's not cooling adequately. A stuck-open heater valve is the root cause of the symptom.
When the heater control valve outlet hose is as hot as its inlet hose, it suggests the valve is stuck open.
We all overlook things from time to time, but missing these kinds of details make an inadequate cooling complaint tougher to diagnose than it needs to be.