Habernet

Posting from my iPhone so bear with me. Just bought a 2012 civic with 90k miles. Everything else works great but the AC comes on intermittently. When it does come on it does get cold. Sometimes it doesn't come on at all. I'm not too knowledgeable on the subject but I think I can hear the compressor click on and off really fast when it does work and when it doesn't it simply doesn't click on. Just bought this car but has no warranty. Help please!

ezone

Does it fail to work correctly when it's hot outside?
Does it turn on and get cold when it's cooler outside?

Return to the car lot and see if they will look into it? (Even without a warranty many do want a good reputation, but others notsomuch)

Habernet

It's only been hot here recently and it seems to not matter. Sometimes it turns on and sometimes it doesn't. Yesterday it ran for a good 45 minutes and was cold. Today it worked half the time but when it did it also stopped halfway through for 5 minutes and then clicked back on. I've searched google and people say it could be the relay switch, the clutch, all things that sound expensive to me. I plan on at least calling back the lot but I specifically didn't get the warranty because I needed to save the money.

ezone

There's a lot of stuff involved in a car AC system, and just about every item will probably come up in a google search which complicated things. An understanding of how the system works and some pointed observations are needed to effectively narrow down possible causes. Much of this needs checked WHILE it's not working.


When it stops working, open the hood and see if:

A) The compressor clutch is engaged and spinning
B) The radiator fans are running

Habernet

Just turned it on for a second in the parking lot. Ac was working. The clutch engages and radiator fans on. Ac is cold. When it doesn't work the clutch doesn't engage and fans aren't on I think.

ezone

Need to verify this when it doesn't work. Be certain.

Habernet

Okay I'll post back in a bit. I'm working a delivery shift so I'll be driving soon.

ezone

Also need to know which version the car has.....Does the car have manual HVAC, or climate control?

Habernet

It has manual ac.

Habernet

Confirmed the clutch and fan are off when it's not working and on when it is. It seems to go in and out as I drive.

ezone

The blower motor in the dash continues to work when the AC system quits, yes? (If the blower motor quits, the AC system is shut down)


The radiator fans quitting would indicate to me the PCM has either lost the AC request signal, the request was interrupted, or the PCM lost an input that causes it to disable the AC system.

Ok....Any other possible clues? Check engine light on? Other electrical things don't work right or don't work consistently?

Is there any evidence that someone has been jacking around in the dash, or engine compartment, or under the dash? Trying to figure out where the most likely place would be for a human to have made a mistake. Got an aftermarket radio installed? DID it have one before you got the car?


Does the AC light stay on in the control panel when the AC quits working?
Have you tried smacking the HVAC panel with your hand?

Can you associate works/doesn't work with anything, like maybe bumps in the road? I'm thinking an electrical connection is randomly losing contact....

First logical place to check is the engine compartment...There's always a good chance someone had their fingers in it.

I'd check the 3 wire connector that is on top of the alternator, see if it is not fully locked together. (that connector and harness leads down to the compressor)

With the engine running and the system NOT working, I'd gently wiggle wire harnesses in the areas where AC related harnesses and components are. If the AC starts working while you do this, you may have hit upon a significant clue. Then you should be able to figure out how to narrow down a specific wiring branch or something where the least amount of movement has the greatest effect.

There's a system pressure sensor out front next to the condensor and hidden by the front bumper cover.....that might be an item to check wiring on but you probably have to pull the front bumper cover off to reach it.


If you have access to a really good scanner you may be able to see if the PCM is losing its AC request signal from the HVAC panel, or see if there's some other reason the PCM would shut down operation of the AC system....like a coolant temperature reading too high, AC pressure sensor input missing or incorrect, etc. Knowing if the AC request signal is present at the PCM cuts down a lot of guesswork, it effectively cuts the system in half.

Habernet

I think I found the problem. The three wire setup going from the alternator to the compressor is showing on three wires like someone accidentally hit it. If I push on the connection the compressor clicks on and works fine. Do you think I can just wrap it with electrical tape and try to wiggle the connection or should I buy a new wire altogether?

ezone

You mean like damaged insulation, exposing bare wires?

Habernet

Yeah exactly. I'll post pictures tomorrow morning. But when I push down on the connection where the wires are bare it clicks on every time.

ezone

Without seeing the issue first hand....here's some thoughts:


You could have female terminals inside the connector shell that have been damaged, spread out so they can't grip the male terminal and make intermittent contact.

I suppose you can wrap any exposed wires with electrical tape for now.... but being exposed to weather could bring corrosion problems later in its life.

There is also a product called liquid electrical tape that might be used too, simply brush on several coats and it should build up a nice insulating layer that is sealed.

Or just replace the short harness to the compressor (if that's the portion with damage), but it includes the thermal protector, it's a little more than JUST wires so it's not exactly free.
Honda part #38908-RNA-A01

or splice new wire in (beware if you patch it directly into the main harness without any connectors you could cause service problems if it ever needs to come apart)

Habernet

So with your help I fixed the problem. Sealed the three wires and reseated the connection!

Sandman13

Hoping the knowledgeable guy is still here. I am having a similiar problem with my wives Ac. She has a 2013 civic lx sedan. I'll try to list everything it is doing.

Start car and everything works fine. Ac comes on and blows cold. After about 4 minutes the ac clutch disengagaes, fans shut off (blower still running inside) and do not come back for about 10 minutes while running or if you shut the car off for a few minutes and restart. While it was working and not working I disconnected the 3 pin plug on the aternator and have 11.9 volts on one of the three pins at all times that the ac is switched on or off. (Seems like that should change) I would guess it is some type of thermal shutoff but I cannot seem to find a wiring diagram to know what is in that 3 wire circuit beyond the plug on the alternator. Please help if possible.

I also swapped the horn and ac clutch relays to eliminate that. But with the power still in the 3 pin plug I don't believe that even matters.