AC not blowing cold with no bad signs

"UPDATE: I got the car properly recharged (vacuumed out and put frion in). There was actually no frion in the system beforehand.

The A/C is blowing cold now and there is no more hissing noise …but it only blows cold when the engine is at about 2k rpm. The shop I took it to told me that they found a minor leak, the compressor is likely going bad, and quoted me $1400 on replacing the valves, compressor, and condenser. Thoughts? About $950 was just for parts which I know for a fact I could get around half that and may not need to replace the valve? Is there I way I could just seal the leak if I find it?"

Basically the AC does not blow cold in my 2005 Acura TSX and I have no idea why. I figured maybe it just needs a recharge so I buy an A/C Pro kit from my local auto shop to recharge it, yet when I go to charge it from the low pressure valve, it actually is overcharged. So I let out some pressure for it to be at the right pressure and that didn’t seem to make a difference.

What I’ve done:
Had A/C running full blast for about 5 minutes (Fans full speed non-auto [also tried with auto] and as cold as it will go.
Checked low valve pressure. Apparently it is good according to the gauge that came with the A/C pro kit. I checked the pressure without the can of refrigerant attached.
Air compressor is running.

ALSO, I’m sure this is related, when I’m driving there is a hissing noise that comes from the dash or air vents only when my foot is on the gas and the AC is running. It will stop shortly after I turn the AC off or take my foot off the throttle. This would make me think there could be a leak, but then wouldn’t my low pressure be low?

So at the moment I’m really stumped on what to possible do next and I’m trying to avoid taking it to a mechanic for pricey diagnostics. I’d very much appreciate any advice on further troubleshooting/potential solutions.

Here is a video of my engine bay and the sound I can hear in the cabin. You may need to turn the volume up to hear the hissing sound once I’m in the cabin.

Edit: My high pressure was about 44 psi and my low pressure was about 49 psi.

Edit 4: Sound of compressor on vs off.

AC Compressor On

AC Compressor Off

One thing to double check, make sure the radiator cooling fans in the engine compartment are spinning when the AC compressor is turned on. Does the compressor seem to be engaging? Be very cautious when adding in more refrigerant, because overfilling can do a world of hurt to the AC system and your pocketbook. An AC specialist will pump out all the refrigerant into a holding tank, then put back in only the correct amount.

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I haven’t checked the radiator cooling fans. But the compressor is engaging. I will check the radiator fans tomorrow.

AC doesn’t actually cool anything directly. It transfers heat from one place to another. In a car’s case, from the passenger compartment to the engine compartment. But it won’t work if the heat in the engine compartment isn’t quickly dissipated by the radiator cooling fans.

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The radiator fans are running.

Here is a video of my engine bay and the sound I can hear in the cabin. You may need to turn the volume up to hear the hissing sound once I’m in the cabin.

I’m no AC expert, but would that be the expansion valve inside the passenger compartment making the hissing sound?

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I believe the expansion valve is indeed inside the dash. Would that hissing mean there’s a leak in it or is that noise normal? I’ve never noticed such a noise in any other car I’ve owned or been in.

I defer to those who know AC. Anyone?

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I will never understand this line of thinking.

If it needs a recharge, it is leaking refrigerant, so recharging it won’t fix anything. If it doesn’t need a recharge, it’s probably a compressor failure.

In either case, air conditioner work is not for DIYers. If it needs a recharge, have it done with dyed refrigerant so the technician can identify the location of the leak and fix it.

Well if it’s a very minor leak then it may fix it long enough for me not to care about spending $1000 at a mechanic.

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If there is a leak or some other cause like a bad compressor, and the recharging kit costs $20, you’ll end up spending $1,020 instead of $1,000 when you eventually get it fixed. I don’t see the benefit.

I mean if the top off fixes it for a year, then I just end up spending $20 every year instead of $1000 right away. Albeit the leak may get worse over time, but regardless there doesn’t seem to be a leak because when I checked the low pressure valve the pressure was in the good range according the A/C Pro kit.

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You need an AC manifold gauge set to read both the low and high side pressures.

With this tool, it can be determined if there’s a problem with the expansion valve.

Doing anything else is just guessing.



My high pressure was about 44 psi and my low pressure was about 49 psi. From what I’ve heard, this ultimately means I’m probably looking at replacing my AC compressor. Thoughts?

Click below for a 4 - part tutorial on auto AC.

That’s incorrect.

A bad expansion valve can cause that kind of pressure drop.

If the compressor isn’t making any noise, suspect the expansion valve.


What noise would I expect to hear from the compressor? Sorry if that’s a stupid question… I attached a video to my original post with sound inside the engine bay right by the compressor. Maybe you or someone else can hear it?

A failing AC compressor makes a rattling/knocking noise.


Could you show me an example of this?