My 2003 accord 2.4L a/c is not blowing cold air. I have found that there is no power going to compressor clutch. I have followed the Honda service manual and could not find what is wrong. Compressor clutch is in working condition (clicks) by jumping wire between pins 1 and 2 of the clutch relay socket. The line between single clutch power socket and clutch relay is good (by Check for continuity between the No. 2 terminal of the compressor clutch relay 4P socket and the No. 1 terminal of the compressor clutch 1P connector). The relay itself is good by checking each relay and swapping them for testing purpose. Checking the relay socket and found that there is no voltage between the two control pins 3 and 4 in both cases: a/c switch on and off with engine running or off. Measure the voltage between the No. 18 terminal of ECM/PCM connector E (31P) and body ground with the ECM/PCM connectors connected is 12V and the connections are ok. Pin 4 has 12v to ground with key in ignition position II (a/c switch on or off) and 14v to ground with engine running (a/c switch on or off). Pin 3 has no voltage to ground in any situation (engine running or off, a/c switch on or off). What reasons could cause the no voltage between pin 3 and 4 of the compressor clutch relay 4P socket? Please help. Thanks.

 

Try testing each pin to body ground for voltage. You should have 2 pins with 12V.

Can you also give us some wire colors on the relay connector.

 

Thanks PAhonda. The two pins have 12v are pin 1 and 4 when they are measured to body ground individually. Pin 2 and 3 has zero voltage when they are measured to body ground individually. I also measured the voltage between pins. The voltage between pin 1 and pin 2 is 12v. There is no voltage between 3 and 4.
The single line color for the clutch connector is blue-red. The colors for relay connector are not easy identified as they are at the backside of the relay fuse box. I have tried to open it and found it may require dismantle all connectors at the back side. However, I have attached a picture for the reference pin# of the relay socket here when the pin 1 was measured to ground.










I believe we need voltage between the pins 3 and 4 to activate the relay switch (close pin 1 and 2) when a/c switch in on. Am I right on this?
BTW, does the refrigerant pressure have anything to do with this no voltage issue between pin 3 and 4? I have the 70 psi of static pressure at low side with engine on and off.

 

If the a/c is turned off, then your readings are normal. Pin 4 in your description gets grounded to turn on the a/c compressor when the a/c is turned on.

Does any air blow out of the vents when you turn on the heat, a/c, etc?

 

Ground is supplied by ECM at Pin 3. This closes the relay and supplies voltage to comrpessor. There should never be voltage at Pin 3, even when clutch is enabled. If you follow the wiring diagram to pin E18 on the ECU, you see a transistor switches the circuit to closed (ground avialable) or open (ground denied).

ECM may be denying ground because of input from AC Pressure switch (too low system pressure). Have you checked system static pressure? It should be around air temp (degF) of refrigerant pressure. If much less or zero, then you have a leak and system must be inspected, leak located, and repaired, and recharged.

good luck

 

My accord has 65-70 psi static pressure measured at low side when engine is off. Also same static pressure when engine and a/c is on as the compressure is not on (without getting power).

When the A/C button pressed on, it seems the pin 3 does not get grounded as there is no voltage measured between pin 3 and pin 4 when a/c is on. If this is due to low pressure of refrigerent, what is the minium or normal static pressure required?

 

Do both the radiator or condenser fan turn on when you try to turn on the a/c?

Also, in the common diy threads at the top of this forum, there is a link to do HVAC codes on 03 accords. You might want to give this a try.

 

Air blow out of the vents when turn on the a/c button (the button light on).
When the a/c button pressed on, the radiator or condenser fan do not turn on. However, these two fans running when engine gets hot even without a/c on.
I have tried the threads in the common diy, but they are not match my accord 2.4L. How can I do DTC on accord 2.4L LX?

 

This is the HVAC stuff for the accord I was talking about.

https://www.hondaaccordforum.com/for...-code-s-34589/

 

Hi TexaxHonda, thanks for your reply.

My accord seems having issue with Pin 3 ground. Could you tell me more in details how to check the "pin E18 on the ECU"? Any diagram or picture will help.

Also what is the minium or normal static pressure required for AC pressure switch to enable Pin 3 grounded? Where is the AC pressure switch?

Thanks.