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When idling, the A/C blow cold. However, if I open the throttle a little bit and rev it, then let off the throttle, the compressor will do something odd… it will cycle off/on VERY rapidly anywhere from 5-10 times within about 5 seconds (at around 610 +-30 RPM). I think it is because the ECU cut the A/C off to prevent stalling.
Things that I have done:
-Clean IACV
-ECU relearn
-Check idle speed with IACV remove
-New rotor + spark plug + air filter + oil changeBut the problem is still there. Please help me 🙁
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Replies
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It sounds like you may have a low freon charge if your compressor is cycling rapidly.
I would use some A/C manifold gauges and see what type of readings you have.
A/C work is best left to the professionals though with the correct equipment.
Also here is Eric’s Honda Idle video that may help –
Honda Civic Hatchback 1.6L SOHC MFI A/C System
Description:
Battery voltage is supplied through fuse 56 to the A/C compressor clutch relay contacts at all times.
With the ignition switch in ON (II), voltage is applied to the coil of the A/C compressor clutch relay through fuse 17. When you push the A/C switch ON , and the heater fan switch is in position 1, 2, 3, or 4, a “ground” input is provided to the engine control module (ECM) or powertrain control module (PCM) through the A/C thermostat and the A/C pressure switch.
The A/C compressor clutch relay is grounded by the engine control module (ECM) or Powertrain Control Module (PCM). When energized, the A/C compressor clutch relay allows battery voltage to turn on the A/C compressor clutch.
The A/C ON indicator light comes on when the A/C system is requested.
A/C Pressure Switch
The A/C pressure switch is located in the condenser outlet line where refrigerant is in a high temperature/high pressure liquid state. The switch will sense abnormally high or low pressure, and open the circuit. This removes ground, and the compressor will stop running.[quote=”dreamer2355″ post=34866]It sounds like you may have a low freon charge if your compressor is cycling rapidly.
I would use some A/C manifold gauges and see what type of readings you have.
A/C work is best left to the professionals though with the correct equipment.[/quote]
The A/C work fine but when you rev it up and release it quick RPM would drop below normal (~ -30 rpm) then the compressor will cycle on/off.
[quote=”Wrench Turner” post=34867]Honda Civic Hatchback 1.6L SOHC MFI A/C System
[/quote]
from the diagram you can see that the compressor also controlled bu the ECU.
The only thing that i can think of is it ECU switch the compressor off to prevent stalling, because it only do it when when you rev it up and release it RPM would drop below normal then come back up.[socratic method]
Before automatically condeming the (very expensive and non-refundable) ECM, you might want to ask ye’self a few simple questions:
First and Foremost…
Q: what are your system pressures?Q: what inputs does the ECM look in order to command the compressor clutch ON
Q: could the ECM be recieving incorrect data (and therefore making bad decisions on when to cycle the clutch)
Q: is the ECM getting everything else it should? (power and ground)
Q: what components in your a/c system that if found faulty could lead to the symptoms you are describing
Honda ECU’s hardly ever go bad. I would suggest first checking the operating pressures to make sure those are good. In addition it’s the pressure switch that tells the computer when to switch things on and off so if you find the pressures to be good then I might check that next. Anytime you have an issue where the ECU is involved it’s always the very LAST thing you check or replace.
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