turbo ac issues

[TimS]

So I've done a bit of work on my Kjet turbo ac system. It blows cold (low 40s) at idle and around town, but on the freeway it starts getting warm at around 2500rpm and up. I've tried to keep out of boost best I can to see if it makes any difference. When I get off and keep the rpms low it slowly starts blowing cold again.

I have replaced the heater valve and the interior vents are mostly holding vacuum. The compressor seems to be on when I'm on the freeway, I've cycled the ac switch off and on and can see the voltage drop.

New lines. new p-flow condenser, sanden clone, flushed the original expansion valve and evaporator. Adjusted the expansion valve with the allen. 35/240 psi while at idle.
134a

I know that the compressor should cut off when the car goes into full boost. I've checked the wiring diagrams but it is a little vague. I would think that at full throttle it turns off.
Any ideas?

[apachechef]

Vacuum check valve

[TimS]

replaced already

[ZVOLV]

It could be overcharged. 240 PSI is high.

[apachechef]

Originally Posted by ZVOLV

It could be overcharged. 240 PSI is high.

or backwards?

[TimS]

I can check if its backwards, but pretty sure.
I thought if its overcharged the low pressure side would be higher. If its overfilled would it get would it get cold at all? With the new condenser not sure what would be a proper fill amount.
The sticker says 2.9lbs. So I guessed at about 80% of that.

And thanks for any suggestions. Willing to try it all.

[90volvo]

Saw your pressures which seem ok but at what temp was it outside? Also most expansion valve I’ve bought for 134a were 7 turns out. Did you use vacuum pump to pump system down?

[90volvo]

also the evaporator could be freezing up??? But doubt it

[ZVOLV]

I still think 250 PSI (high side) is too high. I like to see the high side only at about 150 PSI.

I was thinking that maybe your high side is going up TOO high and cutting out the compressor at higher speeds/RPMS.

[kyote]

Originally Posted by ZVOLV

I still think 250 PSI (high side) is too high. I like to see the high side only at about 150 PSI.

I was thinking that maybe your high side is going up TOO high and cutting out the compressor at higher speeds/RPMS.

At what temperature?
Pressure readings mean nothing without ambient temp.
OP, also need to be checking at 2k rpm fast idle.
The following is a cheat chart, but if your pressures aren't close ish you may have other issues.

[Duder]

There is no high pressure cutoff switch on a 240 AC system. IIRC the older systems had no pressure switches at all. Later systems have a low pressure cutoff and a high pressure switch that turns on the fan, but doesn't kill the compressor.

OP - your symptoms (low side normal / high side high) might be caused by air in the system, according to a very nice AC troubleshooting chart made by Sanden. If you can get to a shop that has AC recovery equipment you can have it fully evacuated and then recharged.

I would also check the condition of the evaporator (inside the dash) - there is no cabin air filter in a 240, and the evaporators get clogged up with dust, leaves, and other debris. Also check your blend doors and heater valve - there could be a situation where the AC is working fine, but a blend door issue is letting hot air or ambient air come in to the ductwork and cancel out the cooling effect.

[kyote]

Originally Posted by Duder

There is no high pressure cutoff switch on a 240 AC system. IIRC the older systems had no pressure switches at all. Later systems have a low pressure cutoff and a high pressure switch that turns on the fan, but doesn't kill the compressor.

OP - your symptoms (low side normal / high side high) might be caused by air in the system, according to a very nice AC troubleshooting chart made by Sanden. If you can get to a shop that has AC recovery equipment you can have it fully evacuated and then recharged.

I would also check the condition of the evaporator (inside the dash) - there is no cabin air filter in a 240, and the evaporators get clogged up with dust, leaves, and other debris. Also check your blend doors and heater valve - there could be a situation where the AC is working fine, but a blend door issue is letting hot air or ambient air come in to the ductwork and cancel out the cooling effect.

http://www.sanden.com/objects/3_-_Tr...g_-_Web_01.pdf

[kyote]

From the Verdant Volumes (R12, mind).

[kyote]

Also OP, you can use this chart and static charge pressure and temperature to determine if you have air in the system:

[ZVOLV]

As a general rule, i expect to see the high side at about DOUBLE AMBIENT temp. (Degrees F multiplied by 2= approx high side)

Your second pic (Volvo manual) shows high side readings should be under 200 psi.

I work on modern cars, and not old modified/retrofitted systems, so things could be a little bit different. I just know that on the modern cars that I work on, once the high side starts getting above 200 psi, the electric fans start kicking on stronger and the compressor may disengage a little past 200 psi.

[Duder]

Originally Posted by ZVOLV

Your second pic (Volvo manual) shows high side readings should be under 200 psi.

That's only valid for ambient temps of 86 degF and below. At 104F ambient the high side pressure Volvo is saying it can be well over 200 psi as shown in the two tables. TimS needs to specify what ambient temp was when the pressure readings were taken. It stands to reason that somewhere in the 90s it would cross the threshold into 200 psi being acceptable.

Also, TimS, at anything above idle the low side pressure will start to drop and high side will rise, so keep that in mind.

[kyote]

Originally Posted by Duder

That's only valid for ambient temps of 86 degF and below. At 104F ambient the high side pressure Volvo is saying it can be well over 200 psi as shown in the two tables. TimS needs to specify what ambient temp was when the pressure readings were taken. It stands to reason that somewhere in the 90s it would cross the threshold into 200 psi being acceptable.

Also, TimS, at anything above idle the low side pressure will start to drop and high side will rise, so keep that in mind.

The Verdant Volume suggests this should be tested at 2k rpm not idle.

[Duder]

Another thing to check is heat shielding between the turbo and high side AC lines going into the evaporator. On the highway at higher engine speeds you may be heat soaking the refrigerant before it makes its way into the condenser. Granted, you will have more airflow through the engine bay at highway speeds, but also more heat coming out of the engine & turbo for longer sustained periods.

[Duder]

Originally Posted by kyote

The Verdant Volume suggests this should be tested at 2k rpm not idle.

Yeah that's what I was referring to. The pressures will change as engine idle speed changes so it's important to note at which speed the limits are specified.

[TimS]

A lot here
So I did vacuum out the system system.
The temps were in the high 80s with those pressures which seem to match up with the chart. Although looking it seems like the low side is lower. I read that when the system is overfilled the low side starts to bet higher and then it cant ‘ expand’ and cool.
It is 134 which from what I’ve read runs at higher pressures.

I did spend a lot of time fooling around with climate control stuff blend doors and heater valve. It all seems to be working.
Because it is cold at lower speeds, I don’t think the evaporator is covered but can’t say for sure. Is there a way to clean it with out discharging ?
I will check the ambient temp/ pressure. It is possible that I’ve contaminated by not bleeding the gauge lines with 134 before flowing it into the system.
I keep going back to the boost switch cutting out the compressor.

[Duder]

Originally Posted by TimS

I keep going back to the boost switch cutting out the compressor.

Random idea... you could wire up a small LED light on the dash in series with the compressor clutch power wire. That would act as an indicator and let you know if the clutch is still engaged or not while driving.

[ZVOLV]

Originally Posted by Duder

Random idea... you could wire up a small LED light on the dash in series with the compressor clutch power wire. That would act as an indicator and let you know if the clutch is still engaged or not while driving.

Yeah a meter, test lamp, LED, etc into the compressor circuit would tell you if the compressor is being turned off. I thought of mentioning this too.

[Duder]

This is the troubleshooting guide I was referring to. It's quite detailed. Might help.

https://www.sanden.com/objects/SANDE...OSIS_CHART.pdf

[240Redblock]

Was your TXV adjusted for r134a, if not it could be starving the evaporator under load.

[TimS]

Back from the dead ...
So I read the other AC fix that is pretty good. It seems we are on a similar path (I will be upgrading to a bigger E fan next)
So I went back and drained the system, checked that the valve, checked it had 7 turns out, also took it apart to clean it.
I blew out the evaporator and there was some oil that collected in the "u" at the outlet. Just for kicks, I also opened up the bottom line at the condenser, but nothing really came out.
Was able to blow off the evaporator through the recycle air flap, it had some leaf matter but not that bad.

Installed stock receiver/dryer which said it was good for 134a.
Vacuumed for 30 min, let it set for 30 more, good to go.
Added 36 oz of new 134a. Not cold at all.
Added 5 oz more ( maybe condenser held more) not cold.
around 55/225 at 85 and 2K rpm. Give up for the nite.
New plan is to install a new valve.
In the morning check ambient temp/ pressure. Seems good according to chart.
So maybe I should drain and replace Evap valve. Take out 22 oz or so and things start to get coldish.

Take it for a spin, still gets hotter like before. Like heater hot.
Reconsidered heater valve which I already replaced. Checked the in/out heater hoses in the cab, all good.
Checked lines in engine compartment. Reversed!

So it looks like the hot water was reverse flowing. The valve I put in is directional. It probably held until the water pump spun up, built enough pressure to overcome valve.

Have removed some more freon and was able to get 28 /160 psi at 83 ambient, 2k rpm.
Infrared gun says low 30's , temp probe says 50's. Not sure which to believe, feels pretty cold. The exit line at the evaporator has condensation.
Most importantly it's good at freeway speed. I think the heater was the main issue. Now I just need to tune the AC

Not really sure how much freon I have in it. Today I was offered the use of a new recovery machine . I may evacuate so I can actually determine how much freon is in it.
It feels like there is only about 24 oz in it. (started 3.5 cans in, 1.5 cans sitting on the bench).
Thanks for all the help.

I think I will make a fabric heat shield with snaps to cover the high pressure line as it enters the cab. I think the exhaust / turbo heat must add some temp.
Also cram in a bigger aux electric fan. Trying to figure out a way to cycle it off when the car is moving. It originally came on with sensor in the rad. I added a a relay to kick it on when the compressor is running. Maybe hook into the idle switch at the throttle?