Racinfan83

98 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. 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. (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. 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. Something is wrong and I don't know what it is...

Former User

Cycling is controlled by the A/C thermostat. Test it.

Does the A/C get cold as it should?

And please stop releasing refrigerant *****-nilly into the atmosphere as a guess to solve the problem.

Racinfan83

It got down to 50 with thermometer in center vent on a 92 degree day. Driving it cools fairly well until taking off from a stoplight or pulling a hill or something. I guess I will have to figure out how to get thermostat out and either put a new one in or test it. As to the other - I have no other way to do it and am not rich enough to let a shop figure it out. Thusly I'm on here trying to get help to figure it out as cheaply as possible...

fcm

No cheap way out of this, the refrigerant will nee to be recovered, so A/C unit can be pulled and opened up to remove A/C thermostat, [more so to reinstall thermostat] and then vacuumed and recharged once repaired. 94

mk378

It is a TXV system. It is not intended to cycle on any pressure. Quit trying to treat it like the CCOT system found in most American cars.

[At this point, you should read up on TXV vs CCOT and understand what you were doing wrong.]

Cycling is based on evaporator temperature. It should cycle off when the air at the vents is about 40. If the evaporator is only reaching 50, the thermostat is working correctly in keeping the compressor on all the time.

Since you have been adding and removing refrigerant the first thing to do is recover and recharge by weight. That is the only way to know for sure the amount is correct.

The pressure switch will be closed at all times in normal operation. It will shut down the compressor if high side goes above 450, which is not normal. Does the condenser fan work?

Racinfan83

Yes condenser fan works. And clutch will disengage when dash switch is turned off and stay disengaged.
And the first 4 years I had it the A/C worked fine and cycled on off about every 30 seconds while driving on highway. That's what I'm having trouble with - it worked fine and cycled. Now it still blows cold but no cycle so the car has no power and gas mileage sucks...

mk378

You need to charge by weight and then evaluate performance.

A TXV system will cycle less-- usually not at all-- when it is low on refrigerant. This is the opposite of what a CCOT system does.

There is no way any A/C malfunction could cost you 6 mpg. That is something else. I would start by checking the spark timing there.

Racinfan83

Ok I can ask on that too. I recently replaced distributor. Jumped the connector passenger side kick panel to get cel to come on, put timing light on it at a bit of an angle toward rear of motor so I could see the V notch and the marks on pulley. Not from straight vertical because I couldn't see it until I went rearward a bit. I set the middle mark of the 3 into the V notch and locked it down. Took jumper wire out of connector.
So does this sound correct?