Automotive Air Conditioning Information Forum (Archives)

atem2144 on Fri May 06, 2011 8:59 PM

Year: 1995
Make: Honda
Model: Civic
Engine Size: 1.5L
Refrigerant Type: 134

The a/c in my 1995 Honda Civic works great, nice and cold. The problem I'm having is after about an hour of use the ac stops coming out of the vents. If you put your hand up to the vent you can barely feel anything coming, but the little bit of that is coming out is cold. I have also noticed that if I turn the fan off and back on, some "snow" will come out of the vent. I have also noticed that when I turn the ac off, the compressor does not disengage. The ac is constantly on even when the button is off. I'm thinking a sensor, but not sure which one. Any help would be greatly appriciated.

GM Tech on Fri May 06, 2011 9:58 PM

Could be the relay is stuck, or the clutch driver is corroded on to the pulley- But compressor on all the time explains why it's snowing in your car- and another law of physics, "you can't blow air through ice"

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Fri May 06, 2011 11:06 PM

Constantly on even with the button off suggests a short in the wiring. This system uses negative logic where the button connects the control wire to ground through the fan switch. The signal then passes through the evaporator temperature sensor and pressure switch to the condenser fan relay (does the condenser fan also run all the time?). The Engine Control Unit has control of the compressor relay. When it sees the condenser fan relay has been grounded it engages the compressor.

It would be important to note if the condenser fan runs all the time. When you unplug the pressure switch on the condenser, does the compressor stop?


Edited: Fri May 06, 2011 at 11:12 PM by mk378

NickD on Mon May 09, 2011 4:45 AM

Most likely problem and the thing that turns off the compressor is a thermistor or capillary tube in the evaporator. Not sure about this year, but one peek tells it all. Suppose to switch off the compressor if the evaporator temperature drops below 33*F, then switches it on again after it rises to 39*F. Car also has a TXV for some evaporator temperature control, but it slow down the refrigerant flow, so it doesn't cycle quite so rapidly.

At first the vent air will have a musty odor, at this time with the blower running, the compressor can be manually turned off, then when the vent air start feeling warm, can switch it back on. If the climate control AC switch does not turn off the compressor, also switched on by the blower switch, would be looking for short compressor relay contacts.

Not good to let that evaporator freeze up, serious damage may concern. Another possibility is the face of the evaporator is all covered with debris, these things have got to be cleaned up once in awhile.