I've been suspecting that my air conditioning is faulty, so I've connected one of those Ezi-Chill low side meter to the air conditioning to check the pressure... and here is the results...



when everything is turned off, the low side "static" pressure is 80psi... seems normal...

but when I start the car... but blower fan and air conditioning still turned off, the "static" pressure goes above 100psi, out of my meter's range... (a bit strange?) so I disconnects the meter...

now when I turn on the blower fan to max, and turn on the climate control to maximum, the low side pressure becomes 32-35psi, which based on the surrounding temperature of 26 degrees celcius, is slightly low... (should be 35-45psi)

but here is the mystery, now when I have the car on fast idle 1500rpm, the pressure drops even lower, to below 30psi, and if the engine goes above 2500-3000rpm, the pressure drops below 20psi and the low pressure switch cuts the compressor off....



so based on these symptoms, without connectiing it to a full high/low manifold gauge, does it look like my system is contaminated with air?

 

The system should have freon & gases. So, maybe it's a little low on freon.

 

I've actually just had it regassed couple of weeks ago at a mechanic but it was not a full purge and refill rather just a top up and I think it wasn't done properly...

So the 80psi static pressure isn't enough to conclude there's enough freon in there already?

Does these cars have a sight glass? Where is the high pressure port located as the mechanic couldn't find it?!

 

I have found it hard to get it accurate when you try to "top off" without a site port. The best way to do it is to pull all of the refrigerant out and charge by weight.

 

yeah that's exactly what I'm thinking, if only i could get hold of one of those machines to vacate and pull the system into a vacuum then recharge with oil and gas properly...

 

f88 - what part of the world are you in? If you are close by you are more than welcome to stop by and let's hook my machine up to your car to evacuate and charge.

 

Does the ac work?

 

engatwork: that is extremely extremely generous of you, but unfortunately you're way too far from where I am, I'm all the way down in Sydney Australia...

rspi: it's still working right now, but strangely when the air cond is turned on, the digital reading on the dash that shows the ambient temperature raises consistently up to 50C +... and comes back down if I turn the air cond off... I'm suspecting someone have relocated the sensor in the wrong position? As the Volvo manual mentioned the digital reading is the temperature near the surface of the road? So the sensor should be very close to the ground and not be affected by the heat generated by the air conditioner? So where can I find this ambient temperature sensor?

 

Most of those sensors are clipped in the air scoop under the bumper. The look like this:


If the air works, why bother? Don't fix what aint broke.

 

it's just that the ambient temperature sensor will report to go up when the air conditioner turns on, and even if the temperature outside is only 28-30 degrees the sensor will keep going up until 50+ degrees and when that happens, even though the temperature have cooled down considerably inside the car, the climate controlled blower fan will not to reduce speed because of this, so i'm trying to find out what's causing it to happen..

 

Ok, now that we know what the problem is, can anyone help?

 

Is the in cabin temp sensor working properly?

 

tried to find the ambient temp sensor, but can't find it around the air scoop, where does the sensor connect? maybe I can try to find it by tracing the wires?

hi tech: where do I find the cabin temp sensor? thanks...

 

The in cabin temp sensor is mounted in the dash. It is by the switches on the dash for the sunroof and trip computer. All the way to the right is a little grill in the dash. The fan/sensor is behind the little grill.

 

hi tech, thanks for the help, I've been busy so haven't been checking, so how do you tell if the cabin air sensor is working?

also how can I trace the location of the external ambient air sensor? thanks again..

 

You can use a flashlight and look through the grill and see if the incabin sensor is working.

 

hi tech: i'm sorry but i don't get it, how does the sensor look when it's working, and how does it look when it's not working??

 

If the fan is working you will see it moving when you look through the little grill in the dash. If it is dead it will not be moving.

 

I'll give that a try later, but wouldn't it be possible that the fan is moving but the sensor is dead?

I'd still suspect the placement of the ambient air sensor first as I can't find it and it's reporting a higher than normal outside temperature most of the time... but I'll let you know how I go..



Edit: just check the interior sensor and the fan is moving
Also I'm pretty sure the exterior sensor is the culprit because at night when the exterior temperature is low to start with, the interior blower fan will power down to a lower level when it gets cold enough inside so the interior sensor should be fine