After checking the car, it was found that the electromagnetic clutch of the air-conditioning compressor was engaged in operation, the engine jitter increased, and the blower's air temperature also decreased. The cooling effect was slightly lower than that of the normal car, but the cooling effect was also acceptable.
Why is the engine jitter so great? Unless the extra load of the engine increases, the engine jitter will increase. At this time, the author suddenly found that after turning on the air conditioner at idle speed, the two cooling fans only operated for a few seconds at a low speed and entered a high-speed state. Since then, they have been operating at a high speed until the air-conditioning switch is turned off. The Buick Excelle fan control circuit is as simple as that.
Why does the fan immediately go into high-speed operation after air conditioning is turned on unless the pressure in the air-conditioning duct is too high? I immediately connected the air conditioning repair pressure gauge and found that after the air conditioning was turned on, the high pressure quickly rose above 2000 kPa. At this time, the fan was running at a high speed, and the high pressure of the air conditioner was increased to more than 3000 kPa after the engine speed was increased. The author doubted whether the refrigerant was increased, so he let go of some of the refrigerant, but the pressure did not drop. The front condenser was cleaned again and there was no improvement. According to the standard refueling amount, re-vacuum refilling was performed. It was found that the cold car pressure was almost normal, but it was slightly higher than the normal value. However, the high pressure of the engine hot car increased accordingly. When the water temperature reached 90°C, the high pressure pressure It rose to 2500 kPa. Then where is the problem?
The author has reanalyzed this strange fault: Under the condition that the normal filling amount of the system and the heat dissipation are normal, the pressure of the air-conditioning system will not be so high, but the problem is why the cold car will be normal and the hot car will In case of increased pressure, the fan will reverse unless the fan reverses and this strange failure occurs. The author then took a piece of paper and tested it behind the fan. When the fan was working, the wind from the right fan was blown to the engine, and the wind from the left high-power fan was blown to the front of the car. Obviously this fan was Reversed.
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