1991 CRX Si was sitting outside for 3 weeks without being started in hot weather.
This problem came up for the first time - AC now blows hot air.
Unlike before, when AC button is pressed, the idle RPM does not change at all.
(when AC was functional, activating the button always brought the idle RPM up)
AC blows hot both at night and during the day, both in idle and on the highway.

SInce is doesnt bring the RPM up, i thought its the button itself, took it apart and cant see anything wrong with it...

Any ideas/ similar experience ?

 

subscribed, im having the same problem. good luck!

 

Is the clutch on the compressor engaging? If the clutch on the compressor is not engaging then the system could be low on gas, or the system pressure switch could be at fault.

 

beerex80, how to check if clutch on the compressor engaging? ( i read i need to hear a click but what do i need to wire?) Plenty of gas in the tank.
While messing with it - i noticed that radiator fan doesnt start even though the car idles for at least 10 minutes - can that be related?

 

get a paper clip and jump you low pressure cut off switch. That will fool the ecu into thinking the system has a full charge. if the compressor comes on, you have a low refrigerant charge. And if you only have one fan it's most likely on when the a/c is operable. You can also take a wire and supply the compressor with a 12 volt source from the battery and you should be able to physically see the clutch move. Spin the clutch part by hand and see if it moves. ITs a very easy a/c system to figure out. let us know

 

beige89civic, thanks for the idea. sorry i keep asking questions, guys - never had to deal with AC before. maybe somebody could draw an arrow on the engine bay shot of where the low pressure cut off switch is? tomorrow i ll start with shorting the relays to see if they got bad under the heat... i even pulled out and checked the resistor from under the glove box, no luck yet... 100 degrees tomorrow ;-)

 

I'm having the same problem with my a/c, where is the relay and fuse for the a/c located.

 

The low pressure switch should be located LF part of the car near the receiver drier. ITs a 2 wire switch screwed directly into the a/c line. I do believe it has 2 blue wires. If your system is low DO NOT LEAVE THE PAPER CLIP IN. IT is only a test. YOu'll burn up your compressor. ANd for jetlags question. It should be fuse 15 and 18 on the interior power distribution center. Relays might be on the firewall near the evaporator lines thats where mine are any way

 

check the relays. i was having the same problem till i switched out the relay with a known good one.

the relays for the a/c are in the pass. front corner behind the headlight. the relay that has a red/black wire running to the compressor is the relay that turns it on. theres another one that needs power also for a/c system to work. thats the relay that the low pressure side switch controls.

make sure both of those relays are working, it will save you hours and hours of searching if you overlook them.


edit: when its daylight tomorow, ill post a pic

 

ehh. checked the relays and other things, but by now i am not 100% sure relays are ok.

looks like compressor clutch is ok - when i run 12v jumper to it, it clicks.

question - should the radiator fan come on right away when the AC turned up?

whats the most trusted way to test condenser/clutch relays?

 

eh, fans dont come on when i turn the AC on...
what does it narrow the search to?

 

I'm having the same problem with my a/c, where is the relay and fuse for the a/c located.

 

If Fans aren't coming on when your a/c is on, your a/c won't be very cold at all unless your going down the highway. Check Relay and wiring. Try and spin the fan blade by hand and see if it's locked up. In the fuse box on the RF strut tower the very top left 15amp fuse is the condensor fan. see if it's blown. YOur fan might be locking up blowing a fuse.

 

If Fans aren't coming on when your a/c is on, your a/c won't be very cold at all unless your going down the highway. Check Relay and wiring. Try and spin the fan blade by hand and see if it's locked up. In the fuse box on the RF strut tower the very top left 15amp fuse is the condensor fan. see if it's blown. YOur fan might be locking up blowing a fuse.


Sorry this was intended for azazello.

 

thank you very much for the input, folks. so far all the fuses are fine as well as relays. the fans arent locked, tried spinning them, they do come on when the radiator becomes too hot at idle. My money is on the pressure switch now. I ll keep you posted.

 

Make sure you refrigerant charge is to capacity. Might wanna think about a R134 retrofit

 

folks, thanks to everybody for the input. It turned out that AC pressure sensor was not working. Changing that for a piece #MT0350 from autozone and adding r134 fixed the problem.
It's blowing cold yo!