AC blowing warm air

Hi all,

I'm posting about a new to me '07 LR3 HSE. Just yesterday started blowing hot air through the vents.

Normally I have good google fu, but I can't make heads or tails out of this AC system

I'm fairly sure I can see the compressor, it's the top middle one on the belt diagram. However as far as high or low pressure hoses, I have no clue which hoses are what in that area.

Can anyone give me a quick write up or a link to where I can make heads or tails of where to check for pressure etc?

I had the engine cover off to see if I can hear the compressor engaging, but really as soon as the AC comes on the only noise I can hear are the fans, and they're quite loud so I'm not sure if the ear test is working out for me.

Cheers!

P.S. Love this truck to pieces.

You would check the pressure at the high and low pressure valves (the little grey caps marked with H and L that are located just to the driver's side of the engine) with a manifold gauge set (the set at Harbor Freight is pretty nice and cheap!).

Regarding the compressor. Most cars, and I assume the LR3 also, will not run the compressor if the pressure is too low, so I would definitely check the pressure first if you can and add some R-134a if it needs it.

Technically speaking, if it is low enough that you are getting zero cold air from the vents, then it might be best to evacuate the entire system and refill from empty (at which point you will actually know the correct amount of R-134a to add). I was having an issue where it would work well most of the time, but would occasionally start to blow warm air. I checked the pressure and it seemed low, so I added about 12 oz of R-134a and it seems to have solved the problem. I know there are others like bbyer who tend to have to add refrigerant every year...

If you want some step by step directions, PM me your number and I'll call and walk you thru the process of recharging the system for around $40 compared to the $150 plu cost at a shop or $200 plus at the dealership.

Super appreciate the offer Disco Mike!

I actually added r134A dyed cans (qty of 2) 2 days ago, before I checked back to the forums.

AC works much better, although it seems a bit weak. I'm not sure what amount the system holds, I may need to add more?

I believe this is good news, as the cabin temp sensor seems to be working great, and the compressor as well. I can't believe I didn't see the h & l caps earlier No idea how I missed that.

I'll leave it as is I think for a week and see if it starts to get weaker, which would tell me 100% that there's a rather large leak. If it's ok after a week, then i'll add more, I'm assuming to keep it under 40 psi on the low end?

many thanks for the replies!

I don't know what size cans you were using, but if they were anything other than 12 oz, then be careful. Even with the rear A/C fitted, the total capacity of the system is just under 32oz of R-134a. You definitely don't want to overfill, and therein lies the rub. You really don't know how much refrigerant is in the system (even by reading the pressure) unless you evacuate the entire system and refill from scratch. If you don't evacuate the system, then the best you can do is guestimate by using a pressure/temp/humidity chart and the manifold gauges.

By the way, according to this thread (**/forum/lr3-28/c-problem-67860 where **=landroverforums(dot)com), which is ongoing right now, the compressor DOES run all the time (though at a very reduced capacity)... even when the A/C is turned off and even when the refrigerant level is low. Sooo, if the refrigerant level is too low for too long, the compressor can probably **** itself since it will not automatically shutoff.

Whelp, I was just about to post that after a few days the warmth has returned, and to be honest given the weather conditions here I won't be missing AC for a good long time. I was just going to leave it and tackle something else for the time being.

However if there is a chance I will **** the compressor, then I'd rather fix it now. Seems like the compressor is good, but I'm venting refrigerant somewhere.

Any obvious places to look first?

I believe that it is common to leak from the rear A/C lines if you have the rear climate control in your car. I'm not sure exactly where, but I believe it somewhere around the rear driver's side of the car, near where the lines run up to the AC unit. Sorry that I can't be of more help, but I haven't had the car long enough to deal with the AC that much.

cmb6s said:

I believe it somewhere around the rear driver's side of the car, near where the lines run up to the AC unit.

Click to expand...

Exactly right.

That, the schreader valves, and the compressor itself are the most common AC issues on this vehicle.

As to damage, if all of the refrigerant leaks out, you will not be circulating any oil, which will eventually damage the compressor, as it is always slightly engaged.

Also remember R134a systems are very sensitive to refrigerant amounts. Unlike the old R12 systems where the more you can pack in the colder the AC would get. With 134a if you have to much it will not cool very well, not enough it has the same result. Honestly I would recommend having a shop use a AC machine to evacuate and recharge the system and making sure the oil level is correct. At my shop we charge around $65 to charge a system that is leak free, I'm sure you can find a shop that can help you at a fair cost. Best of luck!