Thread: Air Conditioning not working, help required..........

I do aircon on trucks for $$$ these days and leaks can be a bitch to find and expensive you can spend hours. I always vac down, then nitrogen pressure test a AC system, you will find systems that will hold one not the other. I did a truck today held pressure and won't hold vac, compressor seal nearly every time. Vac leaks pressure leaks dye leaks soapy water leaks can be very time consuming to find. if the AC techs don't have the right gear. Don't go anywhere that doesn't nitro test

A car like a disco will have a thermistor, not a thermostat on the evaporator,( in the cab ) pull it out of the evaporator and heat it up in your hand, if AC comes back on replace it. Very unlikely thou electronics are very good in HVAC. The thermistor won't be able to be bypassed by shorting wires either. Variable non clutch compressors are painful also it's likely the system doesn't use a conventional high low switch but a pressure sender so it can keep the head pressures down and reduce engine load. A lot of euro cars are very sensitive to pressures I got caught doing an Audi once put 650 gram in a 600 gram system and it shut straight down.

Experiencing poor/intermittent cooling from A/c and am particularly interested in any experiences with a failed refrigerant pressure sensor.
2010 D4 3.0ltr with 160,000km, rear air
Air con cooling poor/intermittent recently.
Non LR specialist with more generic scan tool reported fluctuating system pressures potentially pointing to a/c compressor fault, perhaps just low gas. Called in external a/c specialist who hooked up to low and high pressure ports and diagnosed compressor fault due to pressure differences. Didn't do any further work evacuating and recharging the system so didn't assess gas level - was confident it was compressor fault (kindly no charge)
Decided to get a second opinion from local LR indy specialist (autologic scan tool) before outlaying the big $. They did system evac and recharge, down about 300gr gas apparently. Reported continued pressure irregularities after recharge, advised new compressor required.
Regas resulted in perhaps a little colder when blowing cool air. Compressor is engaging when a/c switched on, low pressure line is cold, vent temps can feel close to "normal" but not consistently...just unreliable/intermittent.
About to bite the bullet when read the workshop manual and learned about the refrigerant pressure sensor. Neither repairer has been particularly interested in the oily dirt build up on the high pressure line on both sides of the pressure sensor and surrounds - a closer look indicates this is definitely the source
Workshop manual lists "refrigerant pressure sensor fault" as a possible cause of "poor or no cooling"
Anyone had a similar experience?
Is it just a leak or a symptom of a failed sensor?
Can I isolate a sensor fault as source of irregular pressures? I don't have a scan tool.
Can I change the sensor without evac of system?
Sensor is about $A100, local quotes start at $A1500 plus labour for new compressor....and I still have an obvious leak from the sensor that needs addressing anyway.
Currently thinking its worth changing out the sensor even if requires system vac and recharge.
Any further thoughts and help greatly appreciated.

Cheers

Originally Posted by gossamer

Just found this video on utube and this guy says they are Sanden so ill take his word that they are good. I found my box actually says SSB on the end.
[ame]https://www.youtube.com/watch?v=6wtE76BrGCU[/ame]
and the company
??????????????

Sanden are good japanese company who have made vehicle aircons for a while. they also make hot water heat pump systems that is like a "reverse" aircon

Originally Posted by MDJ

Experiencing poor/intermittent cooling from A/c and am particularly interested in any experiences with a failed refrigerant pressure sensor.
2010 D4 3.0ltr with 160,000km, rear air
Air con cooling poor/intermittent recently.
Non LR specialist with more generic scan tool reported fluctuating system pressures potentially pointing to a/c compressor fault, perhaps just low gas. Called in external a/c specialist who hooked up to low and high pressure ports and diagnosed compressor fault due to pressure differences. Didn't do any further work evacuating and recharging the system so didn't assess gas level - was confident it was compressor fault (kindly no charge)
Decided to get a second opinion from local LR indy specialist (autologic scan tool) before outlaying the big $. They did system evac and recharge, down about 300gr gas apparently. Reported continued pressure irregularities after recharge, advised new compressor required.
Regas resulted in perhaps a little colder when blowing cool air. Compressor is engaging when a/c switched on, low pressure line is cold, vent temps can feel close to "normal" but not consistently...just unreliable/intermittent.
About to bite the bullet when read the workshop manual and learned about the refrigerant pressure sensor. Neither repairer has been particularly interested in the oily dirt build up on the high pressure line on both sides of the pressure sensor and surrounds - a closer look indicates this is definitely the source
Workshop manual lists "refrigerant pressure sensor fault" as a possible cause of "poor or no cooling"
Anyone had a similar experience?
Is it just a leak or a symptom of a failed sensor?
Can I isolate a sensor fault as source of irregular pressures? I don't have a scan tool.
Can I change the sensor without evac of system?
Sensor is about $A100, local quotes start at $A1500 plus labour for new compressor....and I still have an obvious leak from the sensor that needs addressing anyway.
Currently thinking its worth changing out the sensor even if requires system vac and recharge.
Any further thoughts and help greatly appreciated.

Cheers

Sounds like your repairers are guessing it has to be the compressor!

The oily buildup on the pressure transducer is normally a indication of a leak yes!

The fact it starts cooling then works intermintently does not sound like a compressor fault.

Take it to a LR indy with scan tool

No replacing sensor without evac and recharge.

A while back @landyandy talked about a part / sensor in the AC system that his brother in law replaced fixing the poor AC problem. Was diagnosed by a specialist shop in Perth.

Originally Posted by PerthDisco

A while back @landyandy talked about a part / sensor in the AC system that his brother in law replaced fixing the poor AC problem. Was diagnosed by a specialist shop in Perth.

Yes it’s the variable displacement sensor on the compressor. Costs around $350 to replace. My aircon has done the same thing. Take a few minutes to start cooling and when it is, it’s not that cool. I’m going to get the displacement valve replaced and see how long it lasts.