COOL AT IDLE BUT WARMER WHEN RAISING ENGINE RPM’S
Classic Auto Air Tech tip of the week is “Cool At Idle But Warmer When Raising Engine Rpm’s”. Below we will tell you what to do in this instance.
Make sure the water valve is positioned correctly. The water valve is a directional valve and should be installed with the arrow pointing towards the water pump. If the water valve is connected to the incorrect hose, it allows water to circulate through the system via the heater core overpowering the cooling effect of the a/c coil.
Step 1: Check placement of the water valve, correct if needed. In some cases, changing the location of the water valve may not fix the above problem.
Step 2: If changing the location of the water valve does not rectify the issue the possibly the water valve is permanently damaged and may need to be replaced. To check the integrity of the water valve, completely remove the water hoses for the heater core and loop together (this will remove the heater system completely from the possibilities.) If the system now cools, replace the water valve.
Verify adequate air flow to condenser. For air conditioning systems to function properly, there has to be adequate air flow across the condenser. The function of the condenser is to dissipate heat. Without proper air flow, your system will not cool correctly.
Connect gauges to a/c hoses. The pressures should be with the ambient temp of 90, low side pressures should be between 8-25 psi and high side pressures should be between 160-260 psi. If the low side pressures are normal and the high side pressures are high then there might be an air flow issue.
To test air flow to the condenser
Place a piece of paper on the condenser with the car in idle and see if the paper is held in place. With the car in idle, attach gauges and place a large capacity fan in front of the condenser.
What happens to the pressures?
With car still in idle and gauges attached, pour water down the front of the condenser. What happens to the pressures? If the paper is held in place, you are at least getting some air flow. If the high side decreases during test 2 & 3, then your condenser is not getting enough air which is causing your system to not cool properly. To correct this issue, you will need a more powerful mechanical fan.
Confirm correct refrigerant charge in system. All of our systems should be charged with 24 oz. or 1.8lbs of R134 refrigerant only. If overcharged, you will need to evacuate the system and recharge with the correct amount.