AC blows hot air ONLY AFTER started to drive!

[lucienbond24@yahoo.com]

Hello,
I am in need of some help, please, troubleshooting the cause of the AC in my car not working properly…

I have a 2008 Toyota Yaris.
If I sat in parked position, even for 30 minutes with the AC blasting, I have so much cold air that I cannot stay in the car anymore.

As soon as I start driving three minutes after, the cold air starts to get warmer and warmer until only warm air comes out.
I have attached a gauge to the low pressure valve and when the compressor is running at the beginning is at normal level (green right in the middle), but after I have driven a mile or two, The air starts to less cool and the get warmer.
I park the car with engine and ac stil on at max power, go check the same gauge and it’s now on red almost at max red.

This is one of those gauges that come with the DIY refill kits.

If I leave the car running, as it is on red after about five minutes, the pressure gauge goes right back to normal and the AC starts blowing again super cold air.

Why is the AC not blowing cold air after I started driving?

I really love to do things all on my own And not go to mechanic shops or dealerships; so any help that anyone could give me to fix this AC problem is very much appreciated.

I also have recorded couple of small videos that I could post or send for clarification…

Thank you.

[ex-x-fire]

Is there something block the air flow through the radiator and a/c condenser? Otherwise, I'd have a shop draw down the system to see how low it is, refill with correct amount, and check for leaks and operation.

[lucienbond24@yahoo.com]

Thank you for your answer…

But if something was blocking either one then that something would be blocking it at all times including when I am at idle, right? At idle the AC WORKS great…

And do you mean the Freon or the Coolant? Cause I checked both if freon was low then it wouldn’t work at idle either and coolant I have just over half line…

And leaks I can’t detect any visually…

[ex-x-fire]

Draw down the a/c system and see what's in it. Usually people have the opposite problem, it cools at speed but not at idle.

[lucienbond24@yahoo.com]

What does that mean to ‘draw down’? Does it mean to drain it?


Someone mentioned to me that it could be The blend door actuator.
What is the purpose of that and could that be the cause?

[ex-x-fire]

They use a machine to suck the freon out of the system and measure the weight of it. That's what I mean about draw down.
To check the blend door, remove the glove box door and looks for operation while turning the hot to cold knob.
https://www.yarisworld.com/forums/sh...ad.php?t=63798

[lucienbond24@yahoo.com]

Thank you for that explanation.

Before I go that route, which is the more expensive one, Can I ask about the blend door?
Is that even possible for it to cause the hot air to come into the car only after starting to drive?
Let’s say it is faulty, and I am not even touching it, if I sat in the parking lot at idle and I have plenty of called air, How can that device actually cause hot air to come in the car AFTER DRIVING if I’m not even touching it? How does that operate?

[WeeYari]

There is a pressure sensor mounted on the coolant lines. It's purpose is to shut down the compressor if coolant pressure drops below a certain threshold. Could be that if you are truly loosing pressure while driving, the sensor is triggering a shutdown. The system should be checked with a proper set of gauges as I don't trust the one on a refill can to give you an accurate picture of what's going on.

[lucienbond24@yahoo.com]

Thank you, and I understand.

But I’m curious to know how does the blend door actuator work? If that is indeed faulty, how can it cause the cold air that comes in for 20 minutes straight at idle to turn into hot air ONLY AFTER starting to drive the car?
Isn’t dad just some small mechanical piece / knob that I actually have to touch in order to operate?
Because if it was broken, and that was the cause of my hot air, then I shouldn’t have cold air at idle either !

[WeeYari]

I'm not supporting the possiblity of the blend door playing any role in what you are experiencing.

[lucienbond24@yahoo.com]

I don’t I have a service manual so I am not sure where the exact location is for the pressure sensor and whether or not I have two: one for low and one for the high pressure.

I have a 2008 Toyota Yaris four doors Sedan.

I could attach a small video of the AC lines, but I’m not sure I can…

[WeeYari]

There is only one pressure sensor and it is located on a/c line behind passenger side headlight. If the sensor itself was faulty you would not have any cold air period. My theory is that it is doing it's job and shutting down the compressor under low pressure conditions.

[BLH]

This is from a 2007 Service Manual. AC Charts with a DTC. Yours is probably very similar.

It is a single sensor. Mounted on the block with the sight glass. Has a three wire harness on it.

This DTC [B1423/23] is output when the refrigerant pressure is either extremely low (0.19 Mpa [2.0 kgf/cm2, 28 psi] or
less) or extremely high (3.14 Mpa [32.0 kgf/cm2, 455 psi] or more). The pressure sensor, which is installed
on the pipe of the high pressure side, detects the refrigerant pressure and sends a refrigerant pressure
signal to the air conditioning amplifier. The air conditioning amplifier determines the pressure from the
signals in accordance with the sensor characteristics, and controls the compressor.

[lucienbond24@yahoo.com]

Thank you very much. I found it on the thinner AC LINE right next to cap the has an H on it and right next to something that looks like a small round piece of glass that you can look through.
It has this part number written on it 499000-7880.
I already ordered it from Amazon $26.
Link for it is this (That looks like the part, right?): https://a.co/d/03QRv9hq

Quick question: For the model of my car (08 Toyota Yaris) Do I just unscrew it and replaced it with a new considering that there is pressure on the line ? Is there some type of valve like on tires that doesn’t let the pressure come out by just simply unscrewing it?

[WeeYari]

CANCEL YOUR ORDER.
I've already stated it is working and doing it's job.
You need to get someone with a proper set of gauges and understands how to interpret the readings to see what is going on with your system pressure. You need a proper diagnosis.

[lucienbond24@yahoo.com]

I have read your other message as well but only after I had sent mine saying I bought the part.

So what I think it’s going on is that, somehow pressure gets built not dropped, and the pressure sensor (like the one that I ordered) detects it correctly and shuts down the compressor.

I’m saying that, because to the low pressure refill port, I have attached the gauge I had from a refill can when first starting the car and left it there for the first about 30 minutes > I had constant cold air and the gauge stayed at green level the whole time..
> then I started driving for about 5 minutes with it still attached > warm air started coming through inside of the car >
> then I pulled over leaving the engine on and AC still at max power (with inside air)
> when I looked at the gauge it was now in the RED zone all the way to highest pressure point.
> THEN I actually left itstill attached and car still running with AC at max and after about 5 /10 minutes the gauge needle DROPPED BACK into green zone and cold air started flowing again in the car.


So yes, likely it is NOT the pressure sensor which detects the high-pressure and turns off the compressor, but the question is what causes that high-pressure buildup ONLY during the driving of the car?

A proper set of gauges will tell me the same thing I assume; But it cannot tell me what causes the pressure buildup, can it?

Is it possible that the pressure sensor is actually faulty and when the high pressure ‘hits it’ , it fails to send that signal properly to the air conditioning amplifier and then to the compressor?

[WeeYari]

Gauges are going to give you precise pressure readings on both the high and low pressure lines and may tell a different story than a simple colour coded gauge from the refill can sitting on the low pressure side. That is the ONLY way to see if you do have pressure readings out of spec triggering a shutdown. I've had a total sensor failure, which is a very rare occurrence. I cannot see a partial failure occuring here.
I don't believe we have a valve on the sensor housing which closes as the sensor is being removed. Pull out the sensor and you're discharging to the environment. Ultimately you'll have a technician involved in this dilemma of yours.

[lucienbond24@yahoo.com]

So if the readings are good and within parameters then what is the fix?

And if the readings tell me that I have too much pressure then what’s the fix?