V70 XC Air Conditioning

[Retired MVS Contributor]

Actually, you can go over 30 PSI from what I read. It's just that the AC performs best at around 30 PSI. Mine was charged to 50 PSI by the "Volvo specialist". Well unless we checked it wrong, it's at 50 PSI.

And from what I heard, you can't overcharge if you're charging it from a can.

Actually, you can...What is meant by that opinion is that one can is probably not enough to overcgarge it, but it really is, and follks often heat it to get more in...There is a definite realationship between pressure and temperature with refrigerants, that's why they work the way they do...50 pounds means it is undercharged and it will not produce optimum cooling...The evaporator temperature is only 47 degrees at 50 pounds...Optimum sooling will occur when the evaporator temperature is 32 degrees and that works out to about 30 PSI...As more refigerant is added to a low system, the pressure goes down, not up, because we are reading the compressor's SUCTION pressure, not system pressure...Optimum suction pressure is 30 PSI...

Visit airconditioner.com for very comprehensive info on how A/C works and how to service it...Here is a starting quote from that site...

Basic Charging Procedures
REFRIGERANT CHARGING PROCEDURE IN AUTOMOTIVE A/C SYSTEMS

We recommend reading this procedure completely before charging. You may need information before charging you want to keep handy. Have this procedure with you while charging. Although it can be done by a single person, we recommend having a helper around.

This procedure outlines the steps to perform a complete charge. These steps are not to be used to refill or make partial charges. Toping off requires system parameters monitoring and knowledge, specially in R134a-based system. Excessive gas will harm your system and will keep it from cooling properly. MORE REFRIGERANT DOES NOT MEAN COLDER TEMPERATURES

[JRL]

2 cans is not a 100% complete fill (but will work just fine, only 2 oz shy) so you should be OK and just about right if you're filling a system that's totally empty.

[geokilla]

50 PSI is undercharged? Then how come no refrigerant was going into the low pressure side of the system when we tried to charge it... It all ended coming back out into the atmosphere, making the garage smell. The cabin smelled too...

Heh guess we got a leak somewhere. Been recharging it every year >.>

[Retired MVS Contributor]

50 PSI is undercharged? Then how come no refrigerant was going into the low pressure side of the system when we tried to charge it... It all ended coming back out into the atmosphere, making the garage smell. The cabin smelled too...

Heh guess we got a leak somewhere. Been recharging it every year >.>

You either have to heat the can (risky) so the the pressure in the can exceeds the system pressure and can push it's way in, or, (the right way) rev the engine to about 1500 RPM which will increase compressor suction...Before you let the engine return to idle, you valve the can off or else the system pressure will rise and back up into the can...

The way to find out if it is leaking is with a vacuum...You pump it down to 29 inches then valve off the vacuum pump and watch the pressure for at least 1/2 hour...If the pressure rises, you have a leak...

The figure we are talking about of 50 PSI is assuming that the system is working properly...There are other reasons for a high suction pressure, starting with a bum compressor which can't produce enough suction, a bad expansion valve, or a contaminated receiver/drier...

[JRL]

To clarify what he meant by "heating it".
The R134 goes in nicely when the can is warmed a bit.
Let the can sit in a bucket of WARM (not too hot) water for a couple of minutes and it will flow more freely.
When the can is too hot then it can go in too fast, there's a happy medium here

[volvov70pilot]

Thanks for the replies! [FAN ON = AC SELECTED ON, ON PANEL]

So many of them; but that was my point, the system was running (fan on and the engine running) and the refrigerant went in just fine. Read about 30PSI then I turned off the car and left it for a while, then tested the pressure again (i.e. with fan & engine on) and IT WAS back in the red arc again.

HP Switch is $65 on ebay... thoughts?

[Retired MVS Contributor]

To clarify what he meant by "heating it".
The R134 goes in nicely when the can is warmed a bit.
Let the can sit in a bucket of WARM (not too hot) water for a couple of minutes and it will flow more freely.
When the can is too hot then it can go in too fast, there's a happy medium here

Liquid R-134 has a boiling point of -15 degess F...In a sealed container it will boil off to a vapor until the pressure/temperature index for the given ambient temperature is reached and then it will stop boiling...Heating the can elevates can pressure, forcing the refrigerant out...A dangerous condition exists if the can is heated before it is punctured...Never heat a sealed can, the pressure has nowhere to go...If the can is heated to 150 degrees, a temperature easily reached in a parked car in direct sunlight, the can pressure will be 275 PSI...Don't carry cans of R134 around in the trunk as an emergency spare...

[Retired MVS Contributor]

Thanks for the replies! [FAN ON = AC SELECTED ON, ON PANEL]

So many of them; but that was my point, the system was running (fan on and the engine running) and the refrigerant went in just fine. Read about 30PSI then I turned off the car and left it for a while, then tested the pressure again (i.e. with fan & engine on) and IT WAS back in the red arc again.

HP Switch is $65 on ebay... thoughts?

It's leaking!

[papasven]

Where does this recharging take place? got a pic?

[geokilla]

Where does this recharging take place? got a pic?

https://www.matthewsvolvosite.com/forums ... =1&t=31221



The port is out of focus as I was trying to get the compressor, but you can still see the port.

You either have to heat the can (risky) so the the pressure in the can exceeds the system pressure and can push it's way in, or, (the right way) rev the engine to about 1500 RPM which will increase compressor suction...Before you let the engine return to idle, you valve the can off or else the system pressure will rise and back up into the can...

The way to find out if it is leaking is with a vacuum...You pump it down to 29 inches then valve off the vacuum pump and watch the pressure for at least 1/2 hour...If the pressure rises, you have a leak...

The figure we are talking about of 50 PSI is assuming that the system is working properly...There are other reasons for a high suction pressure, starting with a bum compressor which can't produce enough suction, a bad expansion valve, or a contaminated receiver/drier...

How would I pump it down to 29 PSI then valve off the vacuum pump? And if it's at 50PSI, adding more would raise the pressure even more wouldn't it? Or am I not understanding something bout the AC system?

We do know that something's wrong with the AC system. But we're not going to fix it because the cost of fixing it is the value of the car.