Hey guys,

I have a 1996 Civic LX 5-speed and I was diagnosing the AC recently and hit a wall in progress. I found my AC clutch is not engaging and was only working when I jumped the relay with a paper clip at the clutch relay in the fuse box. I tried using some replacement relays with no luck and was able to confirm those relays work as they powered on the cooling fan, etc. I am not sure where to go from here, if the AC clutch ONLY engages when being jumped by a paper clip, and when a brand new relay goes in, the AC clutch disengages. Any ideas or advice on what to check next and how?

Basic issue: AC works when relay is being jumped by the paperclip, and once taken out and replaced by a brand new relay, the AC clutch disengages.



Thank you,

 

If the pressure sensors are bad or not seeing the correct pressure they wont allow the clutch to engage. I had a bad pressure switch that showed open with the meter.

 

Does the condenser fan run when you press the A/C switch button?

 

Thank you I will need to check that, where is that switch located?

 

Yes, the fan runs when I press the AC switch, it originally did not, and I had to get a new one. But this current fan works whenever I press the switch button

 

Was A/C working fine until recently? If so, do this:

Raise front end on stands.
Remove driver-side front wheel.
Remove splash shield to expose the compressor clutch face.
Start engine, and turn on the A/C and blower at highest speed.
Take a rubber mallet or small hammer and gently tap on the face of the compressor clutch a few times.
Does the compressor clutch now engage?

 

The AC in this car never worked since I bought it and now the Florida summer is here and I have to strip in the car when I drive it hahahaah. I tried to engage that clutch when the AC was on with a mallet but it literally does nothing. That is what led me to thinking it was a burnt relay but the relay is fine, and I could only get the AC on by jumping the relay with a Paper clip. I was even thinking about just leaving the paper clip, but I dont know what kind of damage that could cause so I skipped it.

 

As suggested by Swift, the compressor clutch will not engage if all of the refrigerant has leaked from the system. You can test this possibility with a multimeter by determining whether there is no continuity across the A/C pressure switch on top of the receiver/dryer.

 

You are wise.

 

So, look for voltage to that switch? What is the testing I am looking to do on the drier? I know that the AC is fully charged, I just charged it up today after getting the paperclip in there to jump the AC clutch. That allowed the system to take in refrigerant and I was hoping the low refrigerant was causing this issue with the clutch not engaging, but it continued even after filling the system. In my mind, it seemed like it was some type of electrical issue somewhere.

 

You are not measuring voltage.

With the key off and connector unplugged, measure resistance (Ohms) across the two pressure switch terminals. What is the reading?

Please give details about how and why you filled the system with refrigerant and what the static pressure was before and after the procedure.

 

Okay, so I measured ohms on the terminals and it read 1.3 consistent. Regarding the refrigerant system, I had used an AC Pro can I had with the gauge on it. The first reading had the gauge showing 30 psi, after jumping the clutch this went down to about 5, and I had filled it up to 40psi which was blowing cold air with the clutch relay jumped with the paper clip. I had done this since I knew that the clutch doesn't engage if the system is too low on refrigerant and I mistakenly thought that since I was able to get the AC clutch going with the paper clip, that the issue was just low pressure in the system and it would stay working after I was able to fill the pressure back up.

Process:
-Turned car on full AC and full blower speed, and tested the PSI with the AC Pro can it was showing 30psi
-Jumped the AC clutch relay to see if the system would pull in that refrigerant and pressurize, it seemed to, and PSI dropped to 5 and held
-Filled the system to 40 PSI and allowed the system to run for a few minutes, hoping that this was the solution to the issue
-Tested the air in the car and it was reading 68F as opposed to the 98F I was getting before (i foolishly though Huzzah!)
-turned off the car and replaced the paper clip with a new relay and started the car to see if the AC was cold and the clutch would engage now
-No such luck, hot air came out and the clutch was no longer engaged

I apologize for my ignorance on these things, I am learning as I go and still new to repairing vehicles. I really appreciate your guidance!

Thank you,

 

It appears that the A/C system has two separate problems.

1) A refrigerant leak that should be fixed.

2) The compressor clutch won't engage, possibly due to a problem with the ECU or the wire that runs from the ECU to the clutch relay.

Do this test:

1. Look at the circuit diagram I posted. A Blk/Red wire runs from ECU pin A17 to the clutch relay.
2. Unplug ECU connector A, and use a wire to ground the Blk/Red wire at pin A17 in the free connector to the metal frame under the dash.
3. When you turn the key to ON(II), does the compressor clutch engage (click sound)?

 

hello. Is there a follow up on this? I read your conversation and i am experiencing the same problem. Already tried the suggestions and still my AC clutch wont kick. Could it be that the problem is my ECU?