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98 Honda Civic EX. I have the opposite problem of nearly every A/C post. Compressor runs, blows 50 degrees at ambient temp of 92. Condenser fan works. The problem is that the compressor won’t cycle off except by turning dash switch off or stabbing throttle off idle. Which is KILLING the car and probably the compressor as well. I have had this car 5 years and it has always cycled on and off – you can tell because when it cycles on it drags the car down since it is a little 4 cyl. Now it refuses to cycle off except for a couple seconds when you stab throttle off idle. (some kind of low vaccuum switch maybe??) I have gauges and have vented it down to where there is almost no freon in it – still won’t cycle off. It will cycle off when you turn A/C off by dash switch, and when you stab throttle off idle – but then it runs constantly. If you run engine at 3k rpms for awhile the high side pressure will go up to 400+ and low side to like 20. At idle high side reads 245 and low 42. (90+ degrees ambient temp) I know it should be cycling and that high side pressure should not build up that high. Is there more then one “pressure switch” or “cycling switch” or just the one on the dryer? Can that switch cause this problem? If it is that switch can it be changed without losing all the freon?
Like I said – the A/C blows cold but my gas mileage has dropped from 30+ to about 24 and power is lacking because the compressor won’t ever kick out. Never done this before. Something is wrong and I don’t know what it is…
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Your clutch isn’t releasing from the looks of it. There is an electrical portion to the clutch, check the wires to it. Pull up some diagrams and see where they are.
But it does release anytime I stab throttle or if I turn dash switch off and on. I think compressor and clutch are functioning properly – something in the system isn’t telling it to cycle?
It really shouldn’t release when you stab the throttle. Does it stay off when you hit the switch? Or does it just re-engage. The electrical portion tells the clutch to close. So you have a short or as mentioned thermostat that doesn’t respect A/C being off. Power is being applied from somewhere to close the clutch, weak or intermittent if acceleration lets it open.
There may be a thermistor right at the condenser and it’s possible there’s an issue with that. Suggest getting a service manual for your car as it will help a lot including locating and testing this sensor. Or as suggested above, try BBB industries website for the info.
I would back-probe the clutch wire with a DVOM (multimeter) and see if the voltage signal itself is cycling like it’s supposed to. If it is, then there is something mechanically wrong with your clutch. If the voltage signal is not cycling, then you have an electrical issue. A likely cause of this would be a stuck closed A/C compressor relay. That would be step one.
The pressure switch could also cause this and is located on the driver side on a line coming out of the condenser.
ialmanza4 – on that diagram there is a “a/c compressor thermal protector switch” lower right corner of the diagram. Any idea what that does or what it’s “on/off parameters” are? As I see more info from you guys I am leaning more toward the pressure switch since I get over 400 on high side and below 20 on low side at 3k rpms with no cycling. The thermostat on the schematic at BBBind says “off at 37 degrees” and I’m getting 50 degree air out the vent so I don’t know if it is getting cold enough to trip that thermo. I don’t think it’s ever gotten that cold since I’ve had the car. Have to check and see if clutch re-engages after shutting A/C switch off – but I am pretty sure it doesn’t. When it comes to voltmeters and checking stuff like that I am a lost puppy. I have one but very little clue how to use it. I can do most anything mechanically on a car but that is one place I am lost…
Regarding the pressure switch – changing that means all the freon has to come out or not? I know where it is just don’t know if it is going to release the whole charge if I change it?Something you can do without using meter.
With clutch engaged momentarily disconnect its connector, clutch should drop out.
With clutch engaged momentarily disconnect the pressure switch, clutch should drop out.Regarding the pressure switch effect on the compressor clutch. That switch is normally closed until a extremely high maybe 450 psi or low below 32 psi opens it and interrupts power to compressor clutch relay.
Go slow on changing out the pressure switch.If disconnecting the clutch and pressure switch drops out the clutch as expected, then check that the hot/cold valve is fully closing off heater water.
Possible that an elevated evap temp, above 37 degrees, due to heater not closing off entirely.
Other possibilities are thermostat not working, condenser debris,condenser fan, air/water in system.Since it is an older system and if hasn’t been serviced best to have it evacuated, hold vacuum/leak test and recharged to specs.
Sorry my previous post I meant evaporator not condenser- does your car have a temp sensor there? That could cause the system to not cycle the AC..
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