A/c not engauging on 97 civic ex
 

i have a 97 civic and the a/c hasnt been engauging. i press the a/c button and nothing happens.

1.so if i jump the relay under the hood for the compressor, it clicks on. so i know its good.
2. same for the condensor fan as well

now i put all new relays in and still nothing. and ive checked for power on the red wire that goes to the compressor, and there is nothing. also for the pressure switch there isnt any power.

i just got my car back from the shop, they had just re-charged the system and all that good stuff. but still told me i have an electrical problem.

Anyone have any idea how to get it workin correctly? im going to try and swap out my under the hood fuse box. after that ill swap out the ecu. ill keep you guys posted.... its way to effin hot in cali. i NEED MY A/C on MY DD!! :)

Re: A/c not engauging on 97 civic ex
 

Does the A/C button light turn ON?

Check whether fuse 47 or 56 under the hood or fuse 17 under the dash is blown.

If the fuses are fine, check the A/C thermostat and pressure switch.

Re: A/c not engauging on 97 civic ex
 

yes the light turns on.
ill go check the fuses right now

Re: A/c not engauging on 97 civic ex
 

fuse 17 was good.
were is 47 and 56? are they labeled?

Re: A/c not engauging on 97 civic ex
 

Re: A/c not engauging on 97 civic ex
 

there both good wtf

Re: A/c not engauging on 97 civic ex
 

You now might want to check the A/C thermostat located on the evaporator and, if it's fine, then check continuity of the ground wires running from the clutch relay to the ECU and from the ECU to the fan circuit. If those are fine, then the ECU may be bad.

Re: A/c not engauging on 97 civic ex
 

ok ima change out the ecu real quick and see is anythin happens, thanks alot

Re: A/c not engauging on 97 civic ex
 

Actually, given that neither the compressor clutch nor condenser fan run, you should first test the A/C thermostat:

Attachment 469052

Attachment 469053

Re: A/c not engauging on 97 civic ex
 

know where i can by one other than the dealership? i jumped the pressure switch and still nothing. i couldnt find a different ecu. but now when i jump the compressor it doesnt do anything. so im way lost now.

Re: A/c not engauging on 97 civic ex
 

Recheck the three fuses - you may have blown one while messing with the wires. When you can again jump the compressor and fan relays, put everything back to normal and try to jump the A/C thermostat connector (connect BLU/WHT wire to BLU/RED wire in the thermostat connector). If the A/C runs with the connector jumped, then the thermostat is bad. Otherwise, you need to start checking for a broken wire in the circuit with your multimeter.

Attachment 469051

Re: A/c not engauging on 97 civic ex
 

i think i found the themostat(behind the glovebox, facing the front of the car, a blk/yllw, blu/red, and another) is that it? well i had no power to it with my test light and only the blk/yellow wire did have power. but the middle wire(i think the blue/red wire, barely lit up the test light at all.... it was very dim.) and i got the compressor to turn on manually again.

Re: A/c not engauging on 97 civic ex
 

i also found the red wire(to the compressor), on the side where it clips into the harness by the evap and condersor, a little bit of wire showing. and i looked all around where it was to see where it had grounded and i didnt see anything. i looked at the entire harness for other spots where wires would be showing but thats the only spot. ughhh. lol

Re: A/c not engauging on 97 civic ex
 

i tried jumping the a/c thermostat and still nothing.

Re: A/c not engauging on 97 civic ex
 

At this point, can you still jump the respective relay to make the condenser fan run and the compressor clutch engage? If so, take a look at the circuit diagram posted earlier. Use a multimeter to check for continuity of the BLU/WHT wire between the A/C thermostat and condenser fan relay. Do the same continuity test for the BLU/RED wire running between the A/C thermostat and heater control panel.

Re: A/c not engauging on 97 civic ex
 

I think you found the problem. Your test results on the A/C thermostat wires suggest a problem with the BLU/WHT wire that runs between the condenser fan relay and the A/C thermostat. You should have measured battery voltage on both the BLK/YEL wire and the BLU/WHT wire in your test. You should have measured little or no voltage on the BLU/RED wire, as you did.

Re: A/c not engauging on 97 civic ex
 

so the problem is the blue/white wire? what should i do?

Re: A/c not engauging on 97 civic ex
 

You first need to verify the problem. Can you borrow or obtain a multimeter so that you can measure both voltage and resistance/continuity? Otherwise, you can purchase a digital multimeter for about $15-$20.

Unplug the connector to the A/C thermostat and turn the key to ON(II). Use the multimeter to measure voltage to body ground (=dash metal frame) at the pin for the BLK/YEL wire or BLU/WHT wire. You should read battery voltage at each pin. If only the BLK/YEL wire pin has battery voltage, the next step is to locate the problem in the BLU/WHT wire. Start by inspecting the pins of the condenser fan relay and its connector for damage. Do the same for the A/C thermostat. I'll tell you other tests later if no problems are found there.

Re: A/c not engauging on 97 civic ex
 

I had an afterthought. Look at the circuit diagram. I think you should also remove the condenser fan relay and check for battery voltage at pin 4 for the BLK/YEL wire.

Re: A/c not engauging on 97 civic ex
 

i will get a muti meter shortyl and test out the thermostat and the condensor relay. ill keep you posted

Re: A/c not engauging on 97 civic ex
 

So I have a 96 Accord ex and I have been having similar problems except that when my ignition is on and A/C on, my two fans do turn on, which they started to after I added freon. My issue is that my compressor also does not turn on.
I tried to do most of what has been suggested. I checked every fuse with a multimeter. I checked both relays by the radiator and they engage with 12 volts (not with 5 volts off the ecu).
A peculiar part about my problem is that when I have the relay for the compressor plugged in, my ecu A17 compressor connection shows 13.5 volts. It appears to me that when I checked your diagram (which I know could be off for my car) there should be a ground opposite the ecu wire on the relay, but instead it shows battery voltage. I was able to connect the 12volts on the connector to the compressor out and charge the A/C, but I am stumped.
Any thoughts on where I should go next? What is the function of the A17 ACC wire? Is it supposed to ground the relay? RonJ@HT, if you have a diagram on my car like the one for the civic, that would be very helpful.

Thanks for your help!

Re: A/c not engauging on 97 civic ex
 

A17 grounds the compressor clutch relay through C5 and the pressure switch circuit. This circuit is routed through the ECU so that the ECU can ramp up the engine idle to compensate for the increased engine load caused by engagement of the compressor clutch.

Re: A/c not engauging on 97 civic ex
 

So if I'm getting 13.4 volts at the a17 on the ecu side when the A/C is on and the relay is connected, then does it mean that my relay is bad? I tried this with both relays there and it does the same thing.

Further, if they are disconnected if the a/c is off there is no voltage, but if it is on, it shows 5 volts at a17.

Any thoughts on why it would do this?

Re: A/c not engauging on 97 civic ex
 

It's very difficult for me to follow what you are saying.

At the compressor clutch relay, jump battery power to the RED wire going to the compressor. Does the compressor clutch engage?

Re: A/c not engauging on 97 civic ex
 

It does engage when I jump power to it. However, I have to jump it from the black/yellow wire, (number 4 in your diagram above) because the number two is only showing about 2 volts at all times. I was able to charge up the system this way since I had already connected a can of freon and I didn't want to waste it by disconnecting it when the compressor wouldn't turn on.
I know this is bizarre, but maybe it is just a difference between civics and accords of that year range (mine is a 96 accord), but I have 0 volts at the ecu a17 with the air off and 4.96 with it on with the relay disconnected and 13.6 at all times when it is connected.
I tend to think the problem is maybe what you were talking to the other guy about with something under the dash, because the #2 is only showing 2-4 volts. Also, when I use either relay, they both work to turn on the driver side fan when the a/c is on, so I don't believe the problem is with the relays. Also, when I jumped #2 & 4 under the relay and connected it, it doesn't engage the clutch.
As far as #2 wire goes, I don't believe it is a blown fuse, (besides having manually checked continuity on all of them unless there are more than 2 fuse boxes), because it is still showing 2 volts. Even if it was blown, when I jumped power to it, representing the + side of the actuator on the relay, the ecu is giving 5v instead of a negative, so it isn't going to trip the relay.
I just tried grounding the ecu wire while its running and that didn't help either. I probably should also mention that this car used to be an automatic, but I put a 5 speed in there and still have the auto ecu. Also, I am running a turbo setup with an AEM fi/c intercepting a bunch of wires from the ecu. Everything else is running as it should and when I turn on the a/c it revs up the engine as it should, but 5 volts coming from A17??? WTF

I appreciate your help.