It's a rare occasion I request some help or knowledge. Firstly, I'm no aircon expert!

It's my aircon not working. I went to DIY recharge the system and it was showing yellow in the alert section of the gauge. The aircon fan is working OK, the compressor clutch is locating OK. There are no codes on the AC self test system. One indication is the aircon fan runs at a lower temperature than normally.

Sooo, what da yer reckon.

Is it the drier?
Twin pressure sensor?
Ambient temperature sensor?
Is it the condenser or evaporator or their sensors?
Or, I dread to consider, is it the AC compressor? (big ticket item)

Apparently according to the gauge when testing the system it appears to hold pressure OK. The only issue in the last year has been it has needed a recharge by a professional but also my passenger side outlet grill seemed slightly warmer than the driver's side.

Any knowledge or help gratefully received but no expensive guesses please.

Many thanks.

 

I would run dye through it and look for leaks with a black light first.
If the recharge can reads low, then you may likely have a leak.

 

I can offer that the compressor is wired through the pressure switch. If the switch is open due to a pressure problem then the compressor will not run.
If it needed a charge in the last year, then there is a leak. Do you have a set of gauges? The only real way to troubleshoot is to hook up a manifold and see what the pressures are.

Some other things you will want to consider:
Leaks cause the refrigerant to escape. Common places are the condenser, the lines, or the evaporator. You can pressurize with air, or draw a vacuum to see if the system is airtight. Typically the system pressure must remain constant for an hour or so to verify no leaks. As mentioned, dye helps you identify the location of a leak.
A plugged expansion valve or dryer can cause high pressure cut out and poor cooling performance. When the pressure goes high the compressor shuts off to prevent it from going higher. This a vicious cycle which results in no cooling.
If there are no leaks and you're still not getting pressure, this points to a faulty compressor or low refrigerant.
Low refrigerant can also cause icing of the expansion valve and/or evap core, which results in poor cooling.

There are lots of other semi-complex things that must be considered when attempting to repair the system, such as evacuating all the air before filling, using the correct type and amount of PAG oil, etc., but that's some basic info. Google can tell you lots more.

 

 

I can try to help diagnose, but some of your comments I do not understand.

Sounds like you are saying it is not cooling adequately, is that correct? Can you measure temperature on the center outlet?

Compressor runs, correct? Is the large return line cold or sweating condensate?

Sounds like you had a pressure gauge on it (cheap one of the refill can) and it was in the yellow portion? Did it come up to the green when you filled it?

Disco's ac system is remarkably robust. The guys previous comments are good. If it was low, there is a leak, most common areas are condenser and compressor seal. Most of the time you don't even need dye, there will be a conspicuous amount of oil or oily dirt in the area.

Let's go through some is/is not. Is it cooling at highway speeds? Idle? At startup? Does compressor cycle regularly or stay on continuously? How fast does it cycle? Condensate dripping under the truck? All interior blower speeds function normally? Condenser fan running when AC on?

 

Right, firstly, thanks for all the replies guys.

Now here's the update. I took the D2 to a Landrover indy today, he did some tests both pressure and vacuum, nothing wrong, nada. Then he pulled a total vacuum and recharged the D2 AC, it was very cold considering the outside ambient temp. Gregoire, the guy who owns Garage Stand4x4 said he wasn't that happy with the cold at the vents but he expected lower, he had put in 800 whereas the book states 780 plus or minus 25. So, we drove home and measured the temps at home, it measured 10C at all the vents on recirc, that's fine for me considering the ambient today. Gregoire also checked the AC using both a Nanocom and a commercial Hawkeye, both concurred all was OK on the system. Just in case anyone needs to know for future, Gregoire speaks near perfect English and his wife does too, they are avid offroaders and serious trials contenders.

This guy lives for competitive offroading and certainly knows his 'onions' on Landrovers!

 

Is 10°C acceptable for Discos? I get 4°-5° out of my old BMWs when ambient is <32°C. R12, which isn't apples to apples but I ask because I just replaced the condenser and drier in my Disco and will be charging my system in the next week or so. I'd like to know what y'all consider good. The metric conversion is 10°C = 50°F, and 50 sounds high to me.

 

 

The use of old refrigerants like R12, freon etc, are banned in most of the world even possibly in the US except under special circumstances.

If you read RAVE Section 82-14 it explains the heat scale of the ATC ECU in detail. The markings from 16 to 28 plus LO and HI aren't random, they are graduated in degrees celsius. Therefore 16C and LO being the coldest achievable and 28C and HI being the highest achievable. It is all controlled by the boiling point of R134A refrigerant when it changes from fluid to a gas in the fridge process. Sorry, I can't remember what exactly the boiling point is for R134A

https://www.google.fr/search?q=what+...hrome&ie=UTF-8

It also depends on the condition of the AC equipment in the car most of which are 14 years old or more and relative to the ambient temperature externally and what solar gain is achieved in the sun. There is also an non freezing control/sensor to avoid the evaporator freezing up which I believe is set to circa 40F.

 

You can't just go by what coming out of the vent, it all depends on the outside temperature, humidity level and condition of the A/C unit. Most units are designed to pull about 30/40 degrees of heat/humidity out of the cabin area. So, if it is 95°F...you'probably see about 54°F out of the vent. However, if it is 95°F and the humidity level is 70%...then you will see less cooling. The freon can only absorb so much heat and humidity. It is all based of the amount of freon in the system and the size of the cabin area being cooled. The more people you have inside the vehicle will affect cooling performance, too.

If l remember correctly...R134a in its natural state is about -15°F and R12 was -30° and that's why it cooled so much better...it was a colder gas (and the properties of the gas were better at what they do too)...so it could absorb more heat and humidity.

One thing to remember about filling R123a systems...they do not like being over filled. A few oz. to much and they start going the other direction in cooling.

Brian.