A/C is making a hissing noise

Good afternoon,

The hissing may be a leak in the system. If you hear it in the car, it could be the evaporator core leaking.

https://www.2carpros.com/articles/air-conditioner-leak-detection

You need a real set of gauges to read both the high and low side readings while the A/C is running. I need those pressures to help determine the issue.

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

Roy

Okay. It has been hissing for about a year now randomly. And A/C has not been refilled or recharged in my owner ship (5 years) so I wouldn't think it's not really a leak per say. It's a loud hiss that if was a leak i am sure I would be all out of Creon by now. To me it sounds like a clog or value. It sounds as if Freon is been restricted passing though one chamber into another. Could there be a value or switch or filter in-between the system that I could check on that might sound like the above? I do agree that if hearing in the cabin might very well be the evaporator.

Okay, we are back to the gauges. I need to see the reading for the A/C pressures.

Can you rent a set and get them for me?

Roy

Low side reading 105. High side reading 100.

Nice, thank you.

If the A/C clutch is engaged and that is the reading, then the compressor is bad.

If the compressor is not engaged there is an electrical issue. I attached a wiring diagram for you of the compressor circuit.

You will need a test light to do some tests.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Roy

Yes, the compressor is engage. It looks like its spinning pretty good. When the car is off it spins freely one way and does not spin the other way. Not sure if that's normal or not. Thank you for your help!

You are welcome.

I would replace the compressor, expansion valve and the dryer.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

https://www.2carpros.com/articles/replace-air-conditioner-compressor

Roy

Compressor

1. Recover the refrigerant from the refrigerant system.
2. Disconnect and isolate the negative battery cable.
3. Remove the air cleaner housing.
4. Remove the serpentine drive belt.
5. Disconnect the wire harness connector from the A/C compressor clutch coil connector (1).
6. Remove the nuts (2) that secure the A/C suction line (3) and A/C discharge line (4) to the A/C compressor (5).
7. Disconnect the suction and discharge lines from the A/C compressor and remove and discard the dual plane seals.
8. Install plugs in, or tape over all of the opened refrigerant line fittings and the compressor ports.
9. Raise and support the vehicle.


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10. Remove the front end splash shield.
11. Support the A/C compressor (4) and remove the bolts (1 and 2) that secure the compressor and automatic transmission cooler line bracket (3) to the cylinder block (5).
12. Position the cooler lines out of the way and remove the A/C compressor from the engine compartment.

Dryer

1. Recover the refrigerant from the refrigerant system.
2. Disconnect and isolate the negative battery cable.
3. Remove the front fascia.
4. Remove the screw (1) that secures the receiver/ drier mounting bracket (2) to the right end of the A/C condenser (3).
5. Remove the bolt (4) that secures the receiver/drier (5) to the A/C condenser.
6. Disconnect the receiver/drier from the A/C condenser and remove and discard the dual-plane seal.
7. Install plugs in, or tape over the opened receiver/drier fitting and the condenser ports.

Expansion valve

1. Recover the refrigerant from the refrigerant system.
2. Disconnect and isolate the negative battery cable.
3. Remove the bolt (5) that secures the refrigerant line mounting bracket (6) to the left front shock tower (4).
4. Remove the nut (9) that secures the refrigerant line tapping block (10) to the A/C expansion valve (1).
5. Disconnect the wire harness (3) from the A/C pressure transducer (2) to help allow access to the A/C expansion valve.
6. Disconnect the A/C suction line (7) and the A/C liquid line (8) from the A/C expansion valve and position the refrigerant lines out of the way.
7. Remove the dual plane seal from the suction and liquid line fittings and discard.
8. Install plugs in, or tape over the opened suction and liquid line fittings.


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9. Remove the two bolts (1) that secure the A/C expansion valve (2) to the evaporator tube tapping block located within the foam seal (3).
10. Remove the A/C expansion valve from the evaporator tube tapping block and foam seal.
11. Remove the dual plane seal from the evaporator tube fittings and discard.
12. Install plugs in, or tape over the opened evaporator tube fittings and all expansion valve ports.

Today it looks like this. Are we still thinking compressor is bad? It's only 73 degrees out today. Yesterday was 85 or so.

Same result.

The high side should be 2 times ambient temperature plus 15%

The low side should be 25-30 pounds solid.

The fact they are the same indicates a failed compressor.

Roy

About to order the parts listed above with good confidence I can do it my self. With help from shop to discharge and recharge. Question on expansion valve. I can see it in the engine bay connected to the fire wall. Am I going to have to go into the dash or remove the dash to disconnect it from the evaporator? Or does it disconnect and get replaced all from engine bay?

No, you will not. Once the lines are removed, there will be 2 hex bolts that you remove and out it comes.

This is an easy one.

Roy

I do want to say thank you for all your help and detailed instructions got most of the job done this afternoon. I ended up buying a whole new condenser instead of just the dryer. And as you probably know or can see both the transmission line and A/C line used the A/C condenser. I leaked out about 5 oz of transmission fluid plus what was still in the condenser. What would be the proper way to make sure I don't have air in the transmission system? And correct amount of fluid. I do not have a transmission dipstick. Thinking maybe filling the new condenser with fluid and then still adding about 6 oz of fluid to the dipstick whole.

The air will bleed itself out. No need to worry about that. Just make sure the level is good.

Roy

This picture shows fully rev at 2,500 for 20 seconds.

This picture is idle with vent temping at 60 degrees on a 90 day.

Any clue one what's going on? When I sit in my car it's usually 60 degrees coming out of the vent and if I rev my engine it goes down close to 50 degrees.

Okay, put a floor fan in front of the radiator and take the readings again.

the low side is too high. The high side is good.

Did you change the expansion valve?

Roy

Yep, condenser, dryer, compressor, and expansion valve all replaced. I will do that with floor fan and see what it says.

Okay, how much Freon did you add?

Roy

I did not have a scale. Trying to think it told me like 26 oz. I ended up doing almost 2 small cans. tried to leave just a little left in the 2nd can.

This is after fan on it and running about 8 to 10 minutes.

Okay, you are good. The spec is 1.6 pounds which is 2 12 ounce cans.

Roy

I vacuumed it down to -30 for 1 hour and made sure there was 6.5 oz of oil within the system.

Is it normal for the gauge to fall that low when i rev my engine? I should note i put on a heavy duty condenser. But everything said it was compatible.

How much oil did you recover when you did the repairs?

The low side should be 25-30 pounds.

Roy

I didn't not check oil recovery. Figured most was inside either the compressor or condenser when i removed them.

Could this be a sign the evaporator is bad? It is really the only thing that didn't get replace.

The oil in the compressor never comes out. It only will come out when it is removed and drained.

When you recover there should next to no oil recovered at all.

No, to the evaporator. You are good there.

Roy

Okay cool. So it got replace and came with the correct amount of oil in it and got vacuumed down and recharged with maybe an ounce less of Freon than it should have gotten (because I left some in the 2nd can) but it's not cooling good. What should I look into next? The fans seam to run good and adding an extra fan didn't help.. compressor kicks on and is not noisy.

I see a connector on the A/C pipes looks like it might be a A/C pressure switch. Is this something to consider changing. Only 27 bucks. I'm not sure if i would need to discharge and recharge my A/C system to change that.

No, if it was bad the system would not work.

The low side is too high. That is the issue.

I am concerned there is too much oil in the freon system. You said you added 6 1/2 ounces and that is too much. That could be the issue.

You should have only added 3 ounces at the most.

Roy

Okay, so what you are saying is I need to take off the compressor and drain out at least 3.5 oz of oil and recharge?

No, the oil in the compressor is separate from the oil in the Freon system.

The oil in the compressor is fine.

Did you add 6.5 ounces to the Freon system before you charged it?

Roy

No, I'm pretty sure the compressor was 4.2 oz already in it. And I added 3.3 oz Most of it went into the condenser and the rest into the yellow line when I recharged it.

Okay. Sounds about right.

If you take it on a nice drive, does the temperature go down?

Vent temperature should be 60% of the ambient temperature.

Roy

Yes interstate driving can get it down to 45-50 degrees.

Okay, that is good.

Check the radiator and make sure there is no dirt or debris in the fins. It may be restricting air flow at idle and low RPM causing the temperature to rise.

Roy