wittynamessuck

2001 Civic EX CP 5-Speed

Have been having this issue since before it was my car (was my wife's.)

Trying to keep this simple:
AC blows cold, took it to a shop and all readings (low, high, ambient temps, radiator, thermostat) are good.
Can sit for as long as I want and have cold AC.
Can drive around under 2,500rpms (not including acceleration) in any gear and have cold AC.
Freeway speeds/ 3,000rpms or above for a time (5mins or so) in any gear and AC turns off.
When it turns off and I press the clutch the revs hold at 2,500rpms for a few seconds then drop and surge around 1,000rpms and 1,500rpms.
No matter if I turn off the AC (stops surging), keep cruising, stop, turn car off... AC just seems to turn back on when it wants to, normally between 2 and 10 mins.
Yet again, under 2,500rpms for as long as I want with no ill effects.
To add to all this, it ONLY happens when it is over 100 degrees outside.

I'm lost. Not that I am good with AC anyways, but even the mechanics I have taken it too just stare at me. I want to say it is the pressure switch.

I really hope it isn't the compressor I changed it almost a year ago with a reman unit because it threw it's clutch. The AC compressor I got didn't have the pressure switch on it, so I swapped it over.

Before I changed the compressor it never did this. I know everything probably points to the compressor, but I really want to say it is a faulty switch because everything seem to be normal until sustained freeway speeds (the rpms seem to be the key).

Thank you for any help, and I will formally introduce myself with pics of my EM2 in the pics thread.

~WNS

(edit)

OK! Turns out I can simulate it at home in my driveway, took about 3 mins:

Sat and held the RPMs at 3k
Kept doing this weird thing (completely randomly over the course of the 3 mins) where the RPMs would jump to almost 4k without me moving my foot, then drop below 3k, then level
After a few it jumped to 4k and I tied letting off the gas and it was surging! Success!
Jumped out and looked under to verify: While it is revving high on it's own/surging the clutch is NOT engaged.
When it goes back to normal the clutch reengages on it's own and the ac goes back to normal.

My theory is it has to be a sensor or switch or some such thing. When it comes to the compressor itself, it just does what it is told to do. Same with the clutch, it either gets the signal to be engaged or it doesn't. So if the pressures of the freon are good then the compressor itself is doing it's job. So what on earth could be telling the clutch to turn off when x conditions are met?

From what I know there is some kind of pressure switch on the compressor itself, the part I changed over.
There is a relay that tells the compressor/clutch that I have pressed the AC button
AND.... that's it. That's as much as I know.

I guess I need to know what conditions change from 2.5k and 3k RPMs to know which sensor/switch/voodoo is telling the clutch to disengage. Of course now that I know I can replicate it stationary I could take it to a shop... but I don't even let shops change my clutches, so that's out. (the mechanics I talked about before were purely talked to for reference and to point me in the right direction).

Yet again, any help would be appreciated. I know I could just start replacing parts, but I would rather narrow it down and find the problem. Replace 6 things and fix it, if it happens again I don't which of the 6 did it.

~WNS

(edit)

Drove to work in 4th gear just to test a theory.

Even at 4.75k on the freeway for 3 or so miles it never shut off, it was also under 100 degrees this morning.

Sounding more and more like a pressure switch. Now is that something I can change without dumping the system?

~WNS

justinsbg

Give me the details of your vehicle (mileage, make, model) please. Ill get back with you soon about your issue.

wittynamessuck

2001
EX
Coupe
5-speed (notorious 2nd gear syncro issues, not related but there)
150,000 on body
90,000 approx on motor

justinsbg

Forgive but I don't think you mentioned what model you have (civic, accord, ect...). Ill need that as well as whether its a 4cyl or 6cyl. Thanks.

wittynamessuck

For some reason I thought I was on the 7th gen forums, sorry... little less model specific here.

Civic... sorry.

toyomatt84

iTrader: (1)

Look at the Forum you are in, and you'll have your answer.

justinsbg

Ha, should have opened my eyes a little wider. Not only could I have gathered that info from the forum, but he mentioned it at the intro of his description. Sorry about that. Sometimes a look right over things without thinking about it. Ill get back with you early next week with some info. Blessings.

justinsbg

During acceleration, and at or near wide open throttle the PCM is programmed to shut off the compressor for better performance. Maybe that will help you some. I would have to see the pressures when the compressor shuts off to determine what's going on. It doesn't sound like a pressure switch unless it's working like it's supposed to and opening to prevent the pressure from rising to unsafe levels. I would love to help you but I just need some more information. Some cars just can't be diagnosed through text. The symptoms your're describing are just so odd in nature. It could be many things. If you could possibly take a video of the car when it's acting up that would be somewhat helpful.

wittynamessuck

I have a vid I can upload but it is just the car surging while I am going down the road with the clutch pushed in. Unfortunately the monsoon season hit and it has cooled down to the point that it won't turn off.

I will upload what I have when I get home today. In response to what you said, it happens at or above 3k RPMs. I wouldn't think that is anywhere near WOT, and this is during prolonged periods, not acceleration.

I have also noticed that I lose a lot of gas mileage while this is happening. The past few days it has cooled off and the ac has just stayed on my gas needle has barely moved. I use an android app to check my MPG and have seen that when it is acting up I drop to 28MPG, before it was happening I was almost at 35MPG, and now with the past few days I have calculated it a few more times and have gone back up to 32MPG.

I would have said this is just because of AC use, but it was getting used on my drive to and from work since the temp has gone up.

80-100degrees - AC both ways, AC fine 32-35MPG
105-118degrees - AC both ways, AC fine in morning (cooler), Problems in afternoon 28-30MPG

Thank you

wittynamessuck

http://www.youtube.com/watch?v=nP5Qywg5FOY
This was taken yesterday, I got lucky and it happened once.

Like I said, when this starts to happen you can feel that the clutch has let go.

Except for the parts in which I am accelerating that is all the car doing it.

wittynamessuck

If I had the money, in a heartbeat. But thank you.

wittynamessuck

http://www.youtube.com/watch?v=PflIovuDEhE

New info, seems like it is not the AC, but something else and the AC issue is a by byproduct.

So... what could this be?

(edit)
Dammit, I take that back. This just means it isn't the relay causing it. It stops when I hit the AC button, so back to the drawing board.

rdemel

my guess is that its some sort of a temperature/cooling issue under the hood that causes the AC system to disengage since it happens when ur revving it for a period of time and on hot days. (I'm no expert)

Maybe a bad "thermal protector"

justinsbg

Ok, where is your coolant level? Is your reservoir empty? How is the level in the radiator? Do you have to refill your coolant often? Your IAC valve is fluctuating for some reason at idle, I believe if yuo can figure out why, you may find the problem. Check the basics first such as coolant level and air intake leaks. Has any work been done to the car? If so, did this problem start after the work?

wittynamessuck

I have had to burp the system now and then, and put a little water in when I do.

I'm starting to suspect blown head gasket. Not sure it would cause this, but I still need to look into it.

Also when we got the car back from the shop (engine was replaced under a now long gone warrenty) it had idle fluctuations. The shop told us is was someting to do with idle control that they used off our engine, and thus not coverd. We were young and stupid and it is way to late now.

Anyways, no coolant in the oil or oil in the coolant but I will try and rent a comp tester from autozone later.

Man I'm starting to miss my Datsuns.

wittynamessuck

Ya, no way around it. It is my head gasket.

Well, anyone in Phoenix wanna make a couple hundred bucks helping me change it? lol.

justinsbg

If you'll buy my plane ticket I'll come help. I've always wanted to visit Pheonix!!