2005 V8 LR3 approx 150K. AC is not working. bought it in the winter so I have no idea when it last worked. GAP tool fault reads- B1B78-84. I'm not totally versed with my GAP tool but I think I ran live values on the AC system pressure. I was getting a reading of 0. I'll be honest not sure if I was doing it correctly.
What should I be looking for in my GAP tool to figure the issue and 2nd question: If there is no pressure does that mean the compressor is done or could "no pressure" be attributed to anything else? Thanks for any help.

 

There will always be pressure, unless the system has a leak. Get real pressure gauges to check. But you likely have a major leak and are depleted of refrigerant. The compressor always runs, I believe at 5%. Then as cabin cooling is demanded, it increases. PWM setup.

 

Check to see if the hex bolt on the front of the compressor is rotating with the engine running. If it isn't, the front plate is probably sheared off and the compressor is done. That's how mine was when I bought it. If it is rotating, then put some gauges on to confirm 0 pressure. Best case would be a bad pressure sensor.

I learned during my repair that these compressors are positive displacement so they are always rotating with the engine whether on not the A/C is "on".

 

Dovetailing on this AC question - My 2007 V8 with 183K has a leak somewhere. Ive had it "recharged" twice with dye and but no leak is seen on a general check of it. Refilling it seems to last about a year so Ive been okay but its clearly got a leak somewhere. My local mechanic thinks it may be the rear AC that's the issue. Anyone ever deal with this? Thanks

 

Mine had a leak in the rear lines near the suspension compressor. I replaced the o-rings. So far so good.

 

It hadn't struck me that I had an issue until recently I'm not big into using air con but one day it was extremely hot here in Jamaica hotter than usual and I noticed the air con would blow cool when I was accelerating continuously but once I get into any sort of traffic for more than 10 minutes of slow movement or being at idle it starts blowing warm and idk why? Has anyone else had this issue I had changed the air con compressor 5 months ago due to it burning up one random day I had chosen to use it. And is hard to recreate the situation and my car is no longer under warranty it's a 2012 Mazda Axela Sport. Can anyone help??