A/C Acting weird...

[BellyUpFish]

Ok, so..

1997 Acura Integra..

On lower ambient temp days, say 75F and below, I can drive around all day long with the A/C on and it never stops pumping cold air.

When the temps start climbing, I can drive roughly 45 minutes on the highway and the A/C will slowly fade out and stop working and start blowing ambient air.

I use it as a daily beater, commuter and I can almost predict when the A/C will stop working on the way to work during the warmer days. When I get off and drive home in the evening, the A/C works fine.

I've leak tested the system with the UV dye stuff and cannot locate a leak.

Surely we have an A/C expert in the group?

TIA

 

[FowVay]

Check the air gap on the clutch. The clutch is electromechanical and if the clutch is worn then the magnet won't be strong enough to engage the clutch. Heat leads to resistance increase which leads to less efficient operation and ultimately an inoperative compressor.

At the very least, when it stops working hop out and verify that the compressor is turning. If it isn't then you most likely have a worn engagement clutch. You can smack it with a wooden mallet and get it to engage sometimes. It's an easy peazy fix to either shim the clutch or replace it altogether.

 

[TCL]

Are the electric radiator fans coming on?

 

[WobblyElvis]

Does the flow of air from the ducts reduce when this happens? If so, the evaporator could be icing up and blocking the flow of air.

 

[mk378]

What @FowVay said. While it is not cooling, stop somewhere leaving the engine running and the A/C on. Look under the hood for the following: Is the compressor engaged (front plate spinning)? Is the condenser fan running? (I think this is like a Civic where the condenser and radiator are separate, with separate fans, and the condenser is the one on the driver's side). Is the big line leading to the compressor cold, and/or does it have ice on it? Don't touch the small line leading to the compressor, it will be very hot.

 

[Chris142]

Fowvay nailed it. Also could be the ac clutch relay or expansion valve. Start with opening the hood and smacking the clutch.

 

[BellyUpFish]

Sounds like everyone likes Fowvay's suggestion so I'll start there..

To answer a few questions asked:

Yes, radiator and condenser fans are both turning on.
No, the flow of air doesn't seem to reduce at any noticeable level.

 

[spasm3]

Without knowing high and low side pressures, it's hard to know.

Could an undercharge, or overcharge issue.

 

[BellyUpFish]

Without knowing high and low side pressures, it's hard to know.

Could an undercharge, or overcharge issue.

I'd lean heavily on undercharge. Hasn't been touched in 15 years or more... But I would think a complete undercharge wouldn't make it cycle like this, would it?

 

[Chris142]

I'd lean heavily on undercharge. Hasn't been touched in 15 years or more... But I would think a complete undercharge wouldn't make it cycle like this, would it?

It could if the computer sees low pressures.

 

[BellyUpFish]

It could if the computer sees low pressures.

Fair enough. I have very little knowledge in this area..

 

[mk378]

If it gets cold once, the refrigerant should be OK. You're really describing the classic clutch gap problem where the compressor doesn't reliably engage when the compressor area gets hot.

 

[BellyUpFish]

If it gets cold once, the refrigerant should be OK. You're really describing the classic clutch gap problem where the compressor doesn't reliably engage when the compressor area gets hot.

Makes sense give the predictable time issue. I guess it's just getting heat soaked by then enough not to work.

 

[Chris142]

Makes sense give the predictable time issue. I guess it's just getting heat soaked by then enough not to work.

The clutch gap for 99% of the compressors out there is .018-.028... once over about .035 or so they stop pulling in like they should.

 

[BellyUpFish]

The clutch gap for 99% of the compressors out there is .018-.028... once over about .035 or so they stop pulling in like they should.

I'll measure it and see what I come up with. THanks.

 

[BellyUpFish]

Extremely rudimentary question but - should the compressor be turning anytime the AC is selected on or will it cycle?

 

[Chris142]

Extremely rudimentary question but - should the compressor be turning anytime the AC is selected on or will it cycle?

It should cycle

 

[BellyUpFish]

Ok, so I haven’t done anything with this yet. It’s been coolish up until this week and the AC in the car has been keeping up.

Well, drove it to work today and this morning everything was fine for the house drive.

On the way home, at about the given distance it always stops working, it stopped working.

So, I was going to pull over and check the compressor and clutch to see if it was turning.

Pulled over into a parking lot and as I pulled it, it started cooling.

So I kept driving until it got hit again. Didn’t take long.

Started to pull over, and it started cooling.

Did this 2 or three more times, now if I keep the RPM below say 2k, it cools just fine.

Above 2k and it will shut down again.

Does this still sound like the clutch and magnet?

I’ll replace them, just don’t want to start shot gunning parts hoping for the best.

TIA.

 

[mk378]

You should not need to buy any parts here. Remove the clutch plate and take some of the shim washers off of the shaft then put it back together, the gap will be smaller. The exact size of the gap is not important as long as it doesn't drag when off. Since the plate and the pulley tend not to stay flat-- they wear into a set of complementary ridges-- it really isn't possible to measure it on used parts with a feeler gauge.

Though it is good to have a conclusive diagnosis before trying any remedy.

It could also be the compressor relay which should be in the fuse box under the hood. You can swap it with the rear defroster relay they should be the same type.

 

[ZeeOSix]

Ok, so I haven’t done anything with this yet. It’s been coolish up until this week and the AC in the car has been keeping up.

Well, drove it to work today and this morning everything was fine for the house drive.

On the way home, at about the given distance it always stops working, it stopped working.

So, I was going to pull over and check the compressor and clutch to see if it was turning.

Pulled over into a parking lot and as I pulled it, it started cooling.

So I kept driving until it got hit again. Didn’t take long.

Started to pull over, and it started cooling.

Did this 2 or three more times, now if I keep the RPM below say 2k, it cools just fine.

Above 2k and it will shut down again.

Does this still sound like the clutch and magnet?

I’ll replace them, just don’t want to start shot gunning parts hoping for the best.

TIA.

Yeah, it's possible the clutch can't hold strong enough at higher RPM. Maybe have a friend hold the RPM at 2500 in neutral with the AC on while you watch the compressor clutch action to see if it's noticably slipping.