2000 Acura Integra A/C cuts out under engine load

[river_rat]

My wife's 2000 Integra (1.8 liter 4 cylinder) A/C compressor clutch disengages under minor-moderate engine load as if it "thinks" you are at full throttle.
Sometimes it will restart on the highway, sometimes not.
The refrigerant charge is fine and it is dependent on engine load. High RPM in park does not cut it out...It does not appear to be a refrigerant system pressure switch issue.

Sometimes if she accelerates very gently onto the highway with the A/C off, then turns it on, it will work. Any hard throttle in gear kicks off the compressor and it may or may not restart for hours. On low low city streets, it usually but not always engages.

It acts like there is a manifold vacuum A/C cutout switch that has gone bad, but I only have a Chilton's for it, and they decided to print every part of the A/C electrical schematic EXCEPT the compressor clutch circuit...nice job.

Tracing wires didn't get me far as the clutch power wire disappears into a tree of covered wiring harnesses.

Anyone know if this is kicked out directly by the PCM under load? The TPS? Or is there a vacuum switch I'm not seeing?

 

[punisher]

I have seen the following cause those symptoms (not Honda specific):

Bad low pressure switch, bad high pressure switch, bad AC clutch driver in the PCM, high resistance in the AC clutch coil/excessive clutch/pulley clearance.

First thing I check is is for a coil problem. check connector first for corrosion/bad contacts. (Note: Common sense while using stuff under the hood on a running engine) Engine running, turn the AC on, if the clutch doesn't engage, position a long screwdriver or prybar on the front of the AC clutch to check for magnetism. It will be evident. Tap on the clutch face to see if that helps it engage. If it does, verify the clutch/pulley clearance. Over time this gap widens. Reshimming the clutch to the low end of the spec is sometimes enough. If the clutch clearance is in spec, coil is weak.

If there is no pull from the clutch, bypass the low side switch, retest. Same for the high cutout, (assuming it is accessable)

After that, it is kind of a shop only diag. Having a scan tool to ck AC demand status, low/high cutoff switch state, TP voltage etc is really needed for a quick diag (and not tossing a wheelbarrow full of parts at it).

 

[river_rat]

Thanks very much!
I'll look at the clutch magnetism. I don't have a scanner right now, only a code reader. It appears the PCM handles the input power to the entire A/C system, but I don't know if there is a manifold pressure switch imposed between the PCM and the compressor clutch. I am thinking it just reads the MAP and TPS and cuts out power from the PCM. Since the car runs perfectly and gas mileage is normal, I don't think either of those sensors are bad.

Problem is, it only does it under some degree of accelerating or moderate engine load, so that makes it tricky to find.
I can put it in park and run the engine at 3500-4000 RPM for a long time and it stays engaged, so I don't much suspect an A/C refrigerant system pressure switch at this point.

 

[asiancivicmaniac]

I thought this was characteristic of Hondas. My Civic did it as well. It was an 04 and if I accelerated, it would cut the AC for power I assume. It bogged down a bit with it on.

 

[river_rat]

Yeah it is supposed to cut out when punching the throttle.
Problem is, it cuts out at fairly light throttle now and stays out.
I can get it to cut back on driving at 60-70 mph if I slip it into neutral, let off the accelerator and coast. The air will blow cold until I put it back into gear and even lightly speed back up. It stays off (usually) after that.
Somewhat intermittent that way.

 

[ThirdeYe]

I've never noticed my A/C cutting out even when I give it a lot of gas. I typically do turn it off when I merge onto the highway just to give myself a little more power, but I've never noticed it kick off even over 5,000 rpms. Maybe it's because mine's OBD1? It's not Honda specific and it's not normal. The A/C in my sister's Escort ZX-2 is coming on then cutting off, too, and it has plenty of refrigerant.

 

[SteveSRT8]

you may be overlooking a vacuum leak somewhere. Could also be a simple wiring fault.

I would need a manual to be sure as I am unfamiliar with that car's PCM

 

[river_rat]

Yeah, I think I'll have to have a mechanic buddy print off the FSM pages for the A/C at his shop. The Chilton's is weak on that diagram and I'm stuck.

 

[mechtech2]

The throttle position sensor is the one that triggers this.
Most cars have the disconnect at 80% or so. [generally through the computer]
It is NOT RPM related, but throttle position related.
If yours is cutting out too often/too early, this may be designed, or a flaw. This is car specific - ask dealers or internet forums to see if this is normal for your car.

 

[river_rat]

It just started doing this. Maybe the TPS needs cleaned or replaced by now. There is about 160K miles on the car.
I'll ask around on one of my other forum hangouts.
Thanks for the info about the TPS

 

[mechtech2]

If it just started doing this, you almost assuredly have a problem, not a design flaw.
This is actually a GOOD problem to have. More power/economy when you need it at the sacrifice of AC for a tiny bit of time.
Still, I'd fix it for sure. The TPS is used for BUNCHES of stuff!

 

[river_rat]

Not that good of a problem. It stays off for hours once it kicks out. Thanks for the help. I will check the TPS.