Troubleshooting a Honda Civic AC

by Don Bowman


When Honda Civic air conditioning system (A/C) is being diagnosed it must have Freon in the system. If the system has sprung a leak somewhere and the Freon is gone it is no longer an active system that can be checked. A leak would have to be repaired before further diagnosis can continue. Freon can not be released into the atmosphere and must be reclaimed in a machine and reused. There is a major fine for releasing it into the air. For the purpose of this procedure a circuit tester and a set of air conditioning gauges will be needed.

About the A/C System

There are several parts to an air conditioning system which makes it somewhat complex. The main parts of the air conditioning system include: ? Compressor: This raises the pressure and temperature of the Freon. ? Dryer: This removes sediment and captures and retains moisture. ? Condenser: This acts like a radiator and releases the heat to the atmosphere. ? Accumulator: This does the same as the dryer except it is used to also capture liquid Freon so it does not reach the compressor. Depending on the year, the Honda Civic may have a dryer or an accumulator, but never both.
? Expansion valve: This takes high pressure Freon and turns it into a low pressure, low temperature spray that moves into the evaporator inside the cabin and withdraws the heat.


Since there are so many parts involved, the first thing is to test the system from inside the car and see exactly what is happening so there is an appropriate place to start looking for a problem.

If the inside fan does not come on with the A/C, lift the hood with the engine running and the A/C on. Look to see if the compressor is turning and feel the largest A/C hose to see if it is cold. If it is and the compressor is on, the system is all right and the problem is in the blower motor. If the compressor is not on, the problem could be a matter of power to the system, a bad control head on the dash or no Freon. Start by checking the fuses in the fuse and relay panel under the hood on the drivers side. Replace the fuses as necessary.

If fuses were not the problem, hook up the A/C gauges to the system with the red line going to the high side (the small line) and the blue line going to the opposite large diameter low pressure side. The gauge should show close to 80 pounds on the blue low side and 140 on the red high side, depending on outside temperature. This is with the compressor off. It takes this much pressure to turn the low side switch on and allow the compressor to work. At this point the inside fan is a separate issue if the compressor was not on and will be dealt with next.

If the pressure on the gauges was less than prescribed there is a leak in the system and it must be repaired to continue under the hood. The fan is under the passenger side dash close to the glove compartment. Use the circuit tester and check for power at the 2-wire connector on the blower motor (the key and fan need to be on). If there is no power to the fan, the fan is bad. If there is no power, move to the blower motor resister right next to the blower motor. It is usually to the left and slightly to the rear and is used to control the speeds of the fan. Check to see if there is power to the resister. If there is power, the blower motor resister is the problem and should be replaced. This is a very common problem and inexpensive. It can be done without going to a shop. If there was no power it is a bad control head on the dash.

If the A/C system has too little or too much Freon, the high or low side valve will shut the system down to prevent damage to the compressor. If this is the case, a very expensive reclaimer must be used to adjust the Freon level. An ASE technician certification and a MACs card is needed to own one so it must go to a shop for further diagnosis. However if there is Freon in the system the following is a good diagnosis of problems that can be identified:

  1. If there is a clattering noise under the hood with the A/C running, the compressor is going bad and will soon need replacing.
  2. If there is a metal to metal sound like a grinding when the compressor comes on the clutch is bad on the compressor and can be replaced separately.
  3. If the system is not cold enough, feel the large line under the hood for the A/C. If it is warm feel the small line and be careful, if the compressor is working the small line should be hot. If not, the compressor is going bad. If the large line is cool but not cold and the small line is hot the system just needs a recharge.
  4. If the compressor keeps cycling on and off frequently the system is low on Freon and only needs a charge.
  5. If both lines are warm or hot to the touch, the expansion valve is malfunctioning ad it needs to go to the shop.
  6. If the A/C is cold when the car is in motion and warms up when stopped, the condenser fan under the hood is not working.

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