Car AC blowing warm at high Demand

[Reachjayakumarv]

Hi Team,
Greetings.
I am located in India, Chennai(Madras), a warm to highly humid coastal city.
My Car AC is blowing pretty warm at high demand times / hot weather days.

My AC details and a recent gas refill report. image attached that has a report of Robinair AC Recovery Refill machine

MyCarAcCompressorRobinairReport.PNG (200.91 KiB) Viewed 13323 times

And my recent observations of HIGH and LOW side pressures at 18deg C (lowest in car) and 24 deg C (My preference always)

MyCarAcPressureObservations.PNG (27.92 KiB) Viewed 13323 times

What could be the reason(s) for warm blow?
When the car is started from covered parking in the morning, 24deg C setting is pretty good. AC Cools super. park car in hot sun and start driving ac blows hot (high demand)

[Cusser]

You were over 100 grams R134a low when it was re-filled. I wonder if you have leaked refrigerant since then.

Also make sure all your cooling fans are operational.

[Reachjayakumarv]

You were over 100 grams R134a low when it was re-filled. I wonder if you have leaked refrigerant since then.

Also make sure all your cooling fans are operational.

Hi Cusser, thanks for responding. All fans are good. Evaporator core is also very clean shiny (cabin filter replaced promptly).
Robinair report is for the refilling that was done when even 24deg C was a problem. 100g less because previous attempt for manually topping up 134a got into gas escaping because of improper valve mount on a can of 134a. So went for Robinair machine way of refilling using entirely automatic cycle of refrigerant recovery > Vaccuum test for shown time > recharge of refrigerant and the report from that exercise attached here.
As mentioned earlier, morning time @32deg C ext temp car moved away from parking with 24deg C setting cooling is super. And when parked in hot sun let us say 39deg C day, auto cool function On for 18deg C setting just blows hot.
My thinking is given the various pressure readings in the above observation chart, any indication of Expansion Valve problem?
Thanks for reading and responding once again.

[Cusser]

When parked in the sun, remember that seats, dashboard, interior can be alike 140F or more, takes like 15 minutes until the cooling really sets in. Start out with outside air (vent) in because that hot air is COOLER than the interior's air; later switch to recirculate mode.

[Reachjayakumarv]

When parked in the sun, remember that seats, dashboard, interior can be alike 140F or more, takes like 15 minutes until the cooling really sets in. Start out with outside air (vent) in because that hot air is COOLER than the interior's air; later switch to recirculate mode.

Yes Cusser thx for responding. This is also being done at times to vent our heat along.

[Cusser]

Compressor "off" pressures do not tell much.

I see where with compressor engaged, and at high engine rpm, that your highest pressure is 200 psi. I'm in hot Arizona, and all my R134a vehicles typically measure 250-275 psi on the high side.

Feel your lines going into and leaving the firewall, see if they feel cold when your cooling is insufficient. If so, maybe some heater air is bleeding in.

[Reachjayakumarv]

Compressor "off" pressures do not tell much.

I see where with compressor engaged, and at high engine rpm, that your highest pressure is 200 psi. I'm in hot Arizona, and all my R134a vehicles typically measure 250-275 psi on the high side.

Feel your lines going into and leaving the firewall, see if they feel cold when your cooling is insufficient. If so, maybe some heater air is bleeding in.

Thanks Cusser & Geminair for reading further.

Cusser my observations below coincides with your diagnosis (maybe some heater air is bleeding in), I guess...
---

MyCarACproblemExplanation2

MyCarACproblemExplanation2.png (118.64 KiB) Viewed 13255 times

In reference to the above diagram (thanks to the website mentioned and that is the setup I have on my car) When I stick in my hand along the blue bold arrows shown, the evaporator core is in good, cold condition. Did this by removing the Cabin Air Filter, touch & feel the evaporator.
However, after some time of operation of the engine, the Heat Exchanger connection pipes (orange bold lines in the above diagram) of aluminium, are super hot. Cannot hold more than 2sec. Which means by the way of looking at the arrow of the cold air flow shown in the diagram, in spite of the evaporator cooling, the heat exchanger defeats the same.?? Theory says, hot temperature from the running Engine’s coolant gets circulated to Heat Exchanger in regulating the Cabin temperature. I am wondering, are there any malfunctions in the hot coolant flow control to the Heat Exchanger. Any help on this?
My Vehicle is Nissan Micra. Not sure why so much of coolant passing in to the cabin when my external atmospheric temp is between 30 - 37deg C

[Reachjayakumarv]

Compressor "off" pressures do not tell much.

I see where with compressor engaged, and at high engine rpm, that your highest pressure is 200 psi. I'm in hot Arizona, and all my R134a vehicles typically measure 250-275 psi on the high side.

Feel your lines going into and leaving the firewall, see if they feel cold when your cooling is insufficient. If so, maybe some heater air is bleeding in.

Thanks Cusser & Geminair for reading further.

Cusser my observations below coincides with your diagnosis (maybe some heater air is bleeding in), I guess...
---
MyCarACproblemExplanation2.png
In reference to the above diagram (thanks to the website mentioned and that is the setup I have on my car) When I stick in my hand along the blue bold arrows shown, the evaporator core is in good, cold condition. Did this by removing the Cabin Air Filter, touch & feel the evaporator.
However, after some time of operation of the engine, the Heat Exchanger connection pipes (orange bold lines in the above diagram) of aluminium, are super hot. Cannot hold more than 2sec. Which means by the way of looking at the arrow of the cold air flow shown in the diagram, in spite of the evaporator cooling, the heat exchanger defeats the same.?? Theory says, hot temperature from the running Engine’s coolant gets circulated to Heat Exchanger in regulating the Cabin temperature. I am wondering, are there any malfunctions in the hot coolant flow control to the Heat Exchanger. Any help on this?
My Vehicle is Nissan Micra. Not sure why so much of coolant passing in to the cabin when my external atmospheric temp is between 30 - 37deg C

Yes Cusser for your question " Feel your lines going into and leaving the firewall, see if they feel cold when your cooling is insufficient" I missed to answer that my low pressure line coming out of firewall condenses lot of air.

[Reachjayakumarv]

Hi Cusser and Geminair,

Solved the problem!.
Suspecting the AC all these times and probed him a lot on all angles to finally find that the Blender Door Actuator got stuck.

1. After posting the above responses to you, same day night checked the location of the actuator. Removed it and tried moving the gear setup on the Evap, Heater box, which was in the middle position I guess (I do not know which side is open and which side close). It was midnight already, by the time I removed it.

MyBlendDoorActuator1.PNG (79.83 KiB) Viewed 13174 times

2. Drove the car without the actuator next day. Cabin was getting to Very cold temperature. Phew... the Problem is not the AC but of one guy in the whole of the HVAC System!

3. Then during the weekend, Opened the Actuator to see if everything is fine. There was some white grease (Petroleum Jelly??) on the Variable Resistor track. Wiped it clean. And before screwing the actuator to the Evap+Heater box, connected the actuator and switched on the AC to see the actuator works or not. Yes, it worked. And made sure the blend door is also OK by moving by hand so if there were any debris that could be disturbing the door to move easy.

MyBlendDoorActuator2Opened.PNG (179.44 KiB) Viewed 13174 times

4. Screwed the actuator and Switched on the Engine and AC, I could see now when I change the temperature setting of the AC, the actuator moves the door.

Heater temp bleed inputs and the above cited internet article helped in checking this side as well.
Otherwise I was never suspecting heat side, thinking, as we already live in a tropical place, why the car mfr need to provide heating.
When the AC Going too cold in the cabin, made me to understand the need for the Blend Door!!

[Cusser]

I've had to replace an electronic actuator for the blending doors on two GMC vehicles, both stuck in the "hot" position.