Car may not be cooling fast enough

If your car’s A/C system is not cooling you off in a reasonable time frame to make you happy, take it to your service professional for an A/C check-up. Here’s what he or she will look at: • Is the compressor weak? It may build up pressure slowly, or require high rpm to produce normal pressures, so it takes a while to produce adequate cooling. A pressure test should indicate this problem. • Outside air flap not closing. When the system is in Max A/C, the flap should be closed. Unless the flap is closed, hot outside air dilutes the effect of A/C, producing slow cool down. • Is the temperature (blend-air) door operating correctly? This doesn’t have to be an either-it-is-or-it-isn’t proposition.


If the temperature door isn’t in the Max Cool position, the heater core may contribute enough heat to slow down the cooling. Eventually, particularly when the system is set in Max A/C, the A/C may overcome a small heating effect. Even if there is a heater coolant control valve and it’s fully closed, a temperature door even just partly in the wrong position can slow down the cooling by redirecting some of the airflow through the heater. • Heater coolant valve failing to close completely, if at all. The temperature door may be in the right position, but on some systems hot coolant in the core still contributes enough heat to the HVAC case to slow cool down. • Is there a problem with the radiator fan? If it’s a clutch fan, it may be engaging late. If it’s an electric fan, it may be coming on late. In either case, the effect is to reduce airflow (thus affecting cooling), particularly in low speed driving and idle operation.


When the fan finally engages or comes on, the condensing improves and the A/C cooling improves. • Was the system retrofitted? We’re certainly not against retrofit, and we know it’s commonly done when an old compressor fails. But too often, the only parts replaced are the compressor and receiver-dryer, or the compressor, accumulator and orifice tube. On a system designed for R12, unless you do a complete retrofit, performance may be measurably lower. We all know there are many systems that just don’t do well with a basic retrofit, even if it includes a compressor replacement. • Any HVAC case air leaks? If the seals between the case and the cowl are deteriorated, hot engine compartment air gets blown into the case and the passenger compartment. It can take a really long time for the A/C to overcome that. • Slightly low on refrigerant. With some of today’s lower capacity systems, this can account for a huge difference in performance. Today, most systems have capacities of 14 to 32 ounces, so a five-ounce loss is substantial. If this sounds technical and complex, it is!