Hello all,

Just wondering why my low pressure port would be showing less than 20 when I start the car and the compressor kicks on, but then as soon as I try adding r134a (compressor still running), the pressure on the low port kicks up to about 90? could it be my dispenser/gauge? Or something more serious.

I haven't even added half the can of r134a so I don't think that I've added too much, and like I mentioned before, the pressure at the low port shows very low before I try adding any.

Any ideas?

 

jagtoes, thanks for the response, I'll just post what happens here to save from jacking schwalbe's thread.

I just tried again with the same results. With the car off and the pressure reads 80, when I start the car and the compressor kicks on, the pressure drops to less than 15 and stays there. I try to add coolant and 4-5 seconds later let go of the trigger on the dispenser and find that the pressure is now 80 again. When I release the fitting on the low port there is sounds like I'm uncoupling an air hose (hiss and slight release of r134a).

HELP!

 

80-100 psi with the engine off is OK. The system just settles out and the pressure equalizes . When you start the engine and when the compressor turns on the 15 psi is a sign that you are low on freon. In fact if you were that low the compressor should not turn on. To turn on the compressor you need to jumper the low pressure switch and the compressor will turn on. Also make sure you have a fan blowing on the condenser and that the engine is running at around 1500 rpm. Another trick is take a pan of hot water and sit the freon in it while you are charging. The gage should read 20-30-40 psi but not 100 (it might go to 100 if the compressor turns off). If it is that high either the expansion valve or the orifice tube is plugged or not working. If that is the case you would need to fix the problem. You should be at around 30-35 psi and your duct temp. should be around 45-50*.

 

THat all makes sense jagtoes. I just don't understand what is causing the low port pressure (which shows low ~15) to jump up so high every time I try to add coolant. Could it be that the nozzle/fitting on the compressor is clogged and not allowing the r134a to pass to the compressor thus the pressure in the dispenser hose would be high (same pressure as the can itself)? When I unhook the dispenser and then reattach it, the pressure is low again. The hose will dispense coolant when I've briefly tapped the dispenser trigger without it being attached.

Maybe I need a new low port r134a fitting for the compressor?
would hitting the compressor with a shot of r134a cause the expansion valve or the orifice tube to plug up?

I'm just struggling with why the refrigerant is not getting into the compressor and why the pressure is so high, even though I can see the front plate on the compressor spinning and when that turns on it drops the pressure in the low side of the system. Somewhere it seems like something is getting backed up before the coolant can get into the system and the hose is giving a pressure that isn't indicative of the low side pressure.

 

Here's a little reading to see if you can find the problem. Air Conditioning Troubleshooting and Repair

 

Thanks jagtoes. I'm back at it, trying to fix this A/C for the summer. So from the troubleshooting guide here's the options apparantly.

High Suction Pressure
1. Loose expansion valve
2. Overcharged system
3. Expansion valve stuck open
4. Compressor reed valves
5. Leaking head gasket on compressor

Repair options are:
Repair
1. Tighten valve
2. Remove some refrigerant
3. Replace expansion valve
4. Replace reed valves
5. Replace head gasket


Anyone want to take a stab at which is the most likely cause? Also, it's not ALWAYS high, just for the few seconds right after I attempt to push some air into the system. It tapers off eventually.

I'll be replacing the drier and expansion valve. HOPEFULLY that clears it all up. But, I'm afraid it could be the compressor. (reeds or the head gasket?)

 

hello , im having the same problem, system was vacuumed yet when i try to add coolant only a little bit goes in then it stops taking. what could be my problem. yhanks

 

So when you vacuumed down the system did you do it for an hour or two? Also did you replace the orifice valve? Did the system hold vacuum for 24 hours after you shut off the vacuum pump. If all is ok and there are no leaks then fill the system. I usually use 1st shot 134a for the 1st can. Also put the can in a pan of hot water. Adjust the idle to 2000 rpm and put a house fan in front of the rad. Jump the low pressure switch so the compressor runs and keep filling it until the low pressure gage shows 35psi. Should take maybe 1/2 hour. Good luck.

 

What was the solution to this problem?
I have the same problem on a 2007 XC90

Rich

 

I've personally done an R134a conversion for my 940. In the process, I also replaced every component including the under-dash evaporator because I was chasing a leak.

I found that it was not quite proper to refer to documentation regarding specific cars. Since I replaced my condenser and evaporator, I am assuming that my total volume changed from the original spec.

To find the proper charge, make sure you let your car rest until it is totally cool and at equilibrium with the outside temperature (park it in your garage, roll down the windows). Once the temperature has stabilized, check the low side pressure with a gauge with the car off. This will give you a very good indication of the charge in the system. Use an R134a pressure-temperature chart. Find your ambient temperature and where the line matches the pressure, that's what you should be seeing on your low side gauge. Without access to the high side, I believe this is the best way to see your charge.

Use a thermometer right beside condenser to measure ambient temperature. Once you've figured out if your system is under or over charged, move on to charging.

With your problem of the pressure spiking, an initial spike as you open up the can of r134a is perfectly fine, but a sustained, abnormally high pressure is not. My guess it as good as yours with your problem, but I would lean towards a restriction along the fill line. Also make sure your manifold gauges are fully open. On the hand, if r134a is going in, and you can measure the increase in system pressure, then there isn't really a problem, is there?

By the way, when measuring the low side pressure while charging, always reference local ambient temperature and humidity with gauges to get the best estimate of what your low side reading should be. On hot days, you might be surprised at how high the low side gets!

 

When reading the static pressure with the engine off, keep in mind because refrigerant has a temp. pressure relationship, the system could be low and still show the pressures listed on the chart. The gauge just shows there is refrigerant in the system,not how much. A simple example would be;if a 134a can is half empty,it will still show the same pressure as a full can at a given ambient temperature...gotta love science !

 

I own a 2014 Volvo S60 and having similar problems. With the car and air conditioner running it alternates from blowing warm to cool air then back to warm. The compressor is is engaged and running the entire time. My first thought is that it was low on refrigerant. I attempted to charge the system, however when I connected to gage to the low pressure side it showed very high pressure. This is with the car running and the air conditioner on and compressor engaged and it will not accept and refrigerant.


Any ideas what is going on?

Thanks

 

Which engine do you have? Both the 5 and the 6cyl cars have a variable displacement valve on the ac compressor. This valve moves the swash plate in the compressor to change the displacement - controlling the amount of refrigerant compressed - And the amount of cooling supplied.

The valve stops working properly and can cause erratic cooling (like you have) or no cooling even if the system is full. Sometimes it simply takes a long time after the car is running for the ac to become cool, and then it's just sorta cool - not cold. You will need ac gauges and the knowledge to understand them, and VIDA or a compatible scan tool to determine if the valve is getting a signal - to make the proper diagnosis. To replace the valve the refrigerant must be recovered, then the valve is not too difficult to replace. Have seen and replace many bad valves. Sometimes I've found foreign material physically blocking the refrigerant flow on the tip of the valve - perhaps that's why some shops and/or dealers will not replace the valve by itself and insist on replacing the entire compressor.

This is an example of one - there are several part numbers - I'm just using this one for illustration and not suggesting this one fits your car.

https://www.volvopartswebstore.com/p.../31305844.html