Defender AC Blowing Warm? Control Valve Issues Explained

Hey there! I've got some experience working with cars, and this hits close to home. I had a similar issue with my 2019 Discovery last year. The symptoms you're describing sound exactly like what I dealt with, mine turned out to be a refrigerant leak caused by a cracked AC line. I first noticed it when my AC started blowing warm air intermittently. Took it to my regular workshop, and they did a pressure test that confirmed the leak. The whole repair, including labor and refrigerant recharge, set me back about 495 Euro. But before jumping to conclusions, what's the mileage on your Defender? And have you noticed any visible signs of leakage underneath the car (might look like oily spots)? Also, does the AC make any unusual noises when you turn it on? These details would help figure out if you're facing the same issue I had. By the way, has anyone checked the refrigerant levels yet? That should probably be the first thing to look at.

Thanks for sharing your experience! I'm at 142834 KM and just had my service done recently. No, I haven't noticed any oily spots under the car, but that's a good point to check. When I turn on the AC, there's actually no unusual noise, it's more like it's struggling to kick in properly. I was hoping it might be something simple like a relay or fuse, but your refrigerant leak story has me worried now. I'll definitely get the pressure test done first before jumping to conclusions about the control valve. Did your AC also take a while to engage when you had the leak issue?

Yeah, that's exactly what I wanted to ask about the engagement! In my Discovery, before I discovered the leak, the system would sometimes take ages to kick in, super similar to what you're describing. The funny thing is, I also initially thought it was just a fuse or relay problem! From my experience, when the refrigerant is low due to a leak (which was my case), the system's pressure sensor sometimes doesn't detect enough pressure to engage the compressor. That's why it seemed like it was "struggling" to start up. In my situation, the engagement got progressively worse over time until it barely worked at all. But here's something interesting, when my mechanic did the pressure test, they found that the leak in my case wasn't actually that obvious at first. It took them using UV dye to finally spot it. The leak was so small that I never saw those obvious oil spots we usually look for. Since you mentioned your recent service, did they check the refrigerant levels then? Sometimes it gets overlooked during routine maintenance. I learned that the hard way! Before you go for the full pressure test, maybe have them do a quick refrigerant level check, it's usually cheaper and could point you in the right direction. The control valve could still be the culprit, but in my case, fixing that wouldn't have solved the underlying leak issue.

Thanks for all the detailed info! That's really helpful to know about the UV dye test, I had no idea leaks could be that sneaky. You've actually made me feel a bit better about the whole situation. I just called my service center, and you're right, they didn't specifically check the AC refrigerant levels during my recent service. I've scheduled an appointment for next week to get both the refrigerant levels and pressure test done first. Seems like the smart way to go about this rather than just replacing parts and hoping for the best. The way you described the gradual engagement issues with your Discovery sounds exactly like what I'm experiencing with my Defender. Can't believe I almost jumped straight to replacing the control valve! Really appreciate you taking the time to share your experience, definitely saved me from potentially wasting money on the wrong fix!