This paper reports an investigation into a practical cooling issue on a type of fan-forced finned-tube heat exchangers used in Queensland's coal seam gas (CSG) industry. CSG compression facilities in some production sites suffered underproduction in recent summers because of frequent automatic engine shutdowns. The problem is not expected by the manufacturer's design. However, it is suspected of being related to the control systems on the compression facilities triggering the overheating-protection shutdowns due to possible deficiencies in one or some water/gas cooling loops in the facilities' air-cooled heat exchangers. Therefore, to understand which heat exchangers and what exact reasons cause the unexpected cooling issue, an investigation has been carried out on the cooler units of the gas compression facilities. A field instrumentation measurement on one operating cooler unit has been done, followed by an analysis using a one-dimensional analytical model and a three-dimensional computational fluid dynamics model. The experimental results are used to validate both the models. Then the cooling performance of the cooler unit under the summer peak condition is predicted by the verified models. The prediction suggests that the water inlet temperature in one particular cooler section is higher than its upper limit defined by the manufacturer, due to poor cooling at high ambient temperatures. The lower cooling performance is caused by large reductions in the cooler air speed and total heat transfer coefficient, which are related to less efficiency of the cooler fans, more airflow resistance, and fouling on both sides of the finned tubes.