Confused by A/C

[VicVinegar]

The a/c in my 12 year old Civic has appeared to be slowly diminishing in ability since last summer. Last summer it would work fine, until I got caught in traffic on a hot day (90+ deg.) where it would go hot. Once I was moving again it was fine. Only during prolonged gridlock on a highway did it quit.

This summer it quits all the time on a hot day. It worked fine in the morning when it has been 70-75, but afternoon when it has been 90-100 I might get cold air for about 10 minutes before it switches to warm. My thought was it just needed a recharge.

I took it in today for a diagnostic and proper evac/recharge. At first they wondered why it was there (because it works in the morning) and they said the pressure was reading good. I explained these symptoms again and they thought a evac and recharge should do the trick, as I suspected. They evac'd it and found I was 3/4 lb low, so it was recharged and they said they tested it to work.

I just attempted to pick it up and all I got was hot air driving around for 10 minutes. Brought it back and now they are saying the compressor isn't kicking on, although when I was driving it, I still noticed the typical "bump" of about 2-300 rpm when turning the compressor on. The manager is suspecting it is some electronic control now, like what he had to replace in his Accord.

Any thing you guys suggest besides this? They are apparently running some tests right now, so I am waiting to hear what they think will fix it this time. The shop is supposed to be "good" in this area, so I'd hope they aren't just going to throw parts at it. I'm confused because the problems that led me to bring it in never seemed related to the compressor or a control...just 90+ degree temps (and probably ~110 degree ambient on the highway last summer). Even when it was 95 yesterday, it worked for a short time before it faded to warm and then hot. Just seemed like the system that was short on 134 couldn't keep up. Thanks for the suggestions. I'm going to dig into my repair manual, but I wanted to get this up before they call. Trying to keep them honest I guess.

 

[VicVinegar]

It isn't letting me edit, but I also observed the condenser fan working. So according to the Honda service manual so far, the culprit for the compressor not engaging could be the thermal protector or the a/c pressure switch. Maybe they overfilled it?

It appears that if the a/c thermostat was bad, neither the compressor nor the condenser fan would come on. From the wiring diagram, it seems like a bad switch would also not engage either of those items.

 

[VicVinegar]

The shop is saying there is power to the compressor, but the compressor is not kicking on unless you bang on it. He said it needs a new clutch field coil and clutch, but a whole compressor assembly is the same price essentially for the part. They recommend a new compressor. They can't get the part today, so I'll be sleeping on this anyway. Sound legit?

 

[sasilverbullet]

Originally Posted By: VicVinegar
The shop is saying there is power to the compressor, but the compressor is not kicking on unless you bang on it. He said it needs a new clutch field coil and clutch, but a whole compressor assembly is the same price essentially for the part. They recommend a new compressor. They can't get the part today, so I'll be sleeping on this anyway. Sound legit?


Make sure BOTH fans come on when the A/C is on. If they're not, then the thermal switch could be doing it's job.

 

[ComfyShorts]

Originally Posted By: VicVinegar
The shop is saying there is power to the compressor, but the compressor is not kicking on unless you bang on it. He said it needs a new clutch field coil and clutch, but a whole compressor assembly is the same price essentially for the part. They recommend a new compressor. They can't get the part today, so I'll be sleeping on this anyway. Sound legit?


Yes legit, seen this sort of problem on Hondas of all years and models. AC compressor engages fine for some amount of time then cuts out. Happens for few reasons. Either clutch coil intermittently gets an open. Clutch slipping causing thermal protection circuit to disable clutch coil. Or internal short of the clutch coil drawing higher than normal current setting off the thermal circuit again. Replace clutch coil or compressor as unit, doesn't matter which route you go.

 

[VicVinegar]

Well it seems to be acting like they say now. This morning it was about 76 out and it would blow cold, then fade away and start pumping humidity into the car (rear view was foggy at one point), then come back. A couple times I turned it off and back on to see if I could force it to start up, but it didn't seem to be a reliable method.

What confuses me is that this never happened before. Monday morning was probably mid-70s out and humid, and I rolled into the office with a steady stream of cold air. It wasn't ice cold due to the low charge, but cold and consistent. Now it is ice cold and intermittent after having the system charged.

Regarding the fans, the radiator fan comes on in bursts. I've been unable to discover if that is normal or not, but the intervals seems like they are on a clock. Last time I observed it, it would kick on for 45 seconds, then shut off for the same and keep cycling like this. It was strange to me how "clockwork" like it was. I could sit there looking at my watch and at 45 seconds it would switch on everytime and shut off the same every time. With the heat in this area (been over a hundred 5-6 times already this year) I've had no hint of overheating on my gauges, so it appears to be doing its job, I just found the way it operated to be strange.