The schematic below is from the Haynes for the petrol Honda Accord 2003 thru 2007, USA MARKET. I have found most of the sections on engine and transmission to be compatible with my car. In the schematic, I have labeled the relay used by the system to switch the compressor clutch on/off, as B. This relay is a good place to check the compressor.
The picture below shows the location of the compressor clutch relay B in the fuse/relay block.
With the engine off and without the key in the ignition, remove the relay. Removal is made easier by pulling out relays A & C (the two blue Omron relays), after which the compressor clutch relay B can be removed, then replace relays A & C.
The picture below shows the compressor clutch relay removed.
The picture below shows a wire inserted into one of the slots. This slot is the feed to the compressor clutch.
By connecting the wire to the positive battery terminal, the compressor clutch will be energized. This can be done without the engine running, and without the key in the ignition. The picture below shows the other end of the wire on the positive battery terminal. When this is done, an audible clunk should be heard, which indicates that the compressor clutch is working. If you have a DVM, the current is around 3 amps (so gauge of wire is not important). Do not leave the wire like this for more than a few seconds.
If you cannot hear a clunk, then you have a problem with the compressor clutch (either the solenoid is not working, or the thermal protection circuit in the compressor has operated, or possibly the clutch itself is jammed). see here for exploded view of compressor
If you can hear a clunk, perform the next check. Use the wire to bridge across to the slot adjacent and parallel to the slot where you placed the wire earlier.
If you cannot hear a clunk now, then check the compressor clutch fuse (D in the schematic and earlier picture). Remove the fuse using the accessory for pulling fuses, as shown in the picture below.
If you did hear a clunk when connecting the wire to battery positive, and also when bridging to the adjacent slot, then you either have a faulty relay, or the system is not closing the relay.
The picture below shows my relay. This was faulty. I removed the plastic cover and sprayed the relay contacts with switch cleaner, and the relay has been working ever since. This saved me a few £10’s in the cost of a new Honda relay, and it has been working like this for a year now.
The two upper tabs in the picture operate the relay coil, and the two lower tabs are connected to the relay contacts.
The picture below shows how to check a relay. I managed to do this with one hand (other hand is holding the camera). It’s easier with two hands, hold one of the coil tabs against the battery terminal then touch the other coil tab with a wire connected to the other battery terminal.
Obviously, DO NOT let the wire touch both battery terminals at the same time, else you will get a big flash (and a small probability that a battery could explode). If you don’t have a steady hand, don’t attempt this.
If the relay is working, you will be able to feel and hear the contacts closing.
An alternative is to run the engine until the engine cooling fan starts to operate. Then swap the compressor clutch relay with the cooling fan relay (they are the same). If the cooling fan still operates, then the relay was ok.
If you can hear a clunk from the compressor, then it is working. If the compressor clutch fuse is ok, then check the relay.
If the compressor clutch is working, and the fuse is ok, and the relay is ok, then you have a fault elsewhere in the schematic diagram e.g. low gas pressure
HOW TO CHECK IF YOU HAVE ENOUGH R-134a GAS
Remove the compressor clutch relay. Start the engine, and put the aircon to its coldest setting. Make sure you can feel the blower running and air coming through the vents.
Now energize the compressor clutch by connecting the wire from the slot to the battery positive terminal. WARNING, DO NOT LEAVE IT LIKE THIS FOR MORE THAN 30 SECONDS, DEFINITELY NO MORE THAN A MINUTE AT THE MOST, AND DO NOT REPEAT AGAIN FOR ANOTHER MINUTE. IF YOU LEAVE IT LIKE THIS WITH THE ENGINE RUNNING YOU MAY OVER PRESSURISE THE SYSTEM. There is a safety pressure valve in the compressor, but do not rely on it operating !!!
With the compressor clutch energized, if there is enough gas in the system, you will feel cold air coming out of the vents. If you are confident that the compressor clutch relay is ok, then the pressure sensor may be faulty.
However, there could also be other faults that are stopping the system from operating the relay, such as faulty temperature sensors.
see here for locations of temperature sensors
see here for exploded view of heater and evaporator unit
the condenser can also be perished and inefficient (this is in front of the radiator and can be seen through the front grills
- brett, skhell, luvmyaccord and 10 others like this