A/C gurus help (1 Viewer)

[Vasiliy]

Yes my heating valve is new and completely closed, recirc door is good too

Last video just playing with AC manually at idle and high RPM.

 

[smritte]

Now stress test
Outside temp +23(73.4f)
All windows doors is closed, I was under sun. In the next video I will open driver's door and passenger window.

Low side 2.5 bar (36psi)
Nigh side 14.5 bar(210 psi)
Vent temp +12+11(53.6f 51.8f)

This is what we need.
Your high side is showing low. Should be a little higher.
Your low gauge is a bit high. should be lower
a few things could cause this.
1. not enough refrigerant. If you have the "exact" amount installed, your low on oil. If both are correct then #2.
2. The txv is not restricting properly. The txv restricts the low side. It has a sensing device. it tries to keep the evaporator just above freezing. It is either trying to cool off the evaporator due to low system charge or its sticking.

If your low on refrigerant, the txv opens trying to flood the evaporator with refrigerant. This is most likely whats happening. This will cause the low gauge to raise and will lower the high gauge.
If you add refrigerant and "both" gauges go up, the txv is probably broken. This is very rare.

In the picture with the thermisters. The one on the larger line at the firewall. Add refrigerant a little at a time on the low side and watch that temp. It should drop. That is your evaporator temp.

Add some at idle, fan on high, in the low side. raise rpm and watch temp. the temp should drop. do this until it doesn't drop any more.
Watch the high gauge. dont let it go over 300 psi.
If this doesn't get colder, the txv is sticking.

 

[smritte]

My earlier post today, I was running late for work and didn't watch the last video. You see the low gauge pulling down then jump up. That is called cycling. Whats happening is the evap is starting to freeze and a safety switch "cut" the power allowing the pressure to rise and warm the evaporator.
This is a typical "low refrigerant" symptom.

 

[Vasiliy]

My earlier post today, I was running late for work and didn't watch the last video. You see the low gauge pulling down then jump up. That is called cycling. Whats happening is the evap is starting to freeze and a safety switch "cut" the power allowing the pressure to rise and warm the evaporator.
This is a typical "low refrigerant" symptom.

No,I confused you. on last video I was turning On/Off AC myself just to see how pressure works at idle and nigh RPM, that's way arrows was jumping a lot. I will try add more freon then feedback. It's possible my R12 is not real R12, I used digital scale but still it's not enough for keeping good pressure, because even if front TXV is corrupt why then rear AC is not cold too and fridge. So thought about low freon can be right

 

[smritte]

I used digital scale but still it's not enough for keeping good pressure, because even if front TXV is corrupt why then rear AC is not cold too and fridge. So thought about low freon can be right

One of the problems I see when people repair ac is they don't get the oil balance correct. The oil does not move heat but it takes up space. This causes low gauge readings. Too much and you get high gauge readings. If you have the correct amount of refrigerant and the pressure is low, then you don't have enough oil. If your only a little low on oil, you can add more refrigerant. Remember, if you don't have enough refrigerant, you wont be able to move all the heat from both evaporators. If the oil is low, the pressures are low and the system doesn't work properly.

In the mid 90's, they started to outlaw R-12. New "blend" R-12 replacement refrigerants appeared. I encountered about a dozen different types, used a few and met people who used others. We all ran into the same problem, high vent temperatures and odd pressure readings. The blends I used did not move heat as well as R-12. No matter what I did, my vent readings were 50f-55f. In a proper working R-12 or R-134 system, I run the vent temp around 38f-42f. I accept 45f but am not happy with it.

What I'm saying here is, if your not running R-12, that changes everything from pressure to vent temperatures. The only way you can actually tell is with a refrigerant analyzer. Proper ac shops will have one of these.

First, put your temp probe on the suction line (larger one at firewall). You going to add refrigerant slowly and watch the temp.
Add some refrigerant on the low side. Close valve and check. If you can reach the throttle cable when you do this, you can add while holding rpm. Don't worry about the exact speed, just a bit over idle. When checking do not check at idle. It can take a few seconds to stabilize for the reading. Repeat.
Remember to have fan on high. The suction temperature will be close to the low side pressure when this is correct.
At speed if the high side starts staying over 300psi, somethings wrong.

When the refrigerant level is correct the temp will drop. Ideally your looking for 20f-30f. 35f is ok but no higher.

Remember, Idle does not flow enough refrigerant, low fan speed does not add enough heat. These things give false readings.

 

[smritte]

For the other people reading this, automotive ac is taught wrong for some reason. Transport refrigeration, residential, commercial are done by reading evaporator and or condenser, inlet and outlet temperature and pressure.
For example, My home ac. I take the condenser inlet pressure, put a temp probe on the outlet. Convert the pressure into a temperature and if I remember correctly, I should see around a 70 degree drop in temp, inlet to outlet at 85f There are specs given for how much temp change on evaporators and condensers based on outside temp and size of part.
The automotive industry does not give all the specs needed and leaves the technician guessing (I have never found them if they do exist). If they ran the same condenser type on everything you could learn what the "normal" readings are. Evap is too hard to access to test properly. You need one or the other. I tried to build a chart years ago but gave up. Too many differences. Whats sad is quite a few manufacture's use the wrong evaporator/condenser combinations especially with rear ac.. These things must match to work properly. This leaves us with "close enough".

 

[Vasiliy]

Bought this