Tried hooking up my cheesy gauges and they attached, but showed zero pressure. I doubt the system is completely empty, but when I tried to add a bit, it wouldn't take any. do these things need a special fitting to adapt so they can be charged?? I will try a better set of gauges and see if it works I guess.

 

On most vehicles if the system is low on pressure the compressor won't kick in. That, or your pressure sensor could be no-good. Most likely it's low on freon. You can get a little pressure gauge that looks like a tire gauge but fits over an AC nipple to double-check static pressure.

But, what you can do is locate the electrical connector for the pressure switch, unplug it, then jump the terminals with a short piece of wire. Make sure it doesn't contact anything in the engine compartment. It 'should' engage your compressor clutch. If it does, then add some 134. Once you get some into the system to make pressure, remove the jumper and reconnect the pressure switch. Make sure you 'bleed' the lines of your gauges and follow all the A/C charge processes.

 

Tried jumping the pressure switch and still the clutch didn't lock in. I am thinking there may be an issue with the A\C switch on the dash as it doesn't light up when it is pressed. Fuse checks out OK.Possibly when I changed out the blower switch, it may not have been plugged back in.

I tried depressing the schrader valve and nothing came out... not a good sign.. maybe something got damaged on the last off road adventure.

 

Yeah, that's not a good sign. Usually there's 'some' pressure in the system, at least a small amount. Look for signs of oil at the line connections which would be a sure sign of a leak, especially on the high side and the condenser (up front). Could have taken a stick or something.

 

do these systems need PAG oil for the compressor?

 

Probably, but there are different ISO PAG's. I'm not sure what Land Rover uses. What year is your rig? Is there a sticker on your rig's compressor (or other location) that specifies?

 

I dont need it yet but I remember from my Honda having to make sure I put the PAG oil back in otherwise the compressor dies - just figured Id pose the question since it seems this guys system is vacant

But I did find it - it is part#
Denso 10PA
according too:
A/C Compressor PAG Oil Application Chart

the 10P takes PAG 46

there is no 10PA listed

 

ordered a replacement heat/A/C control unit and we shall see when I get it apart. Truck has been doing a lot of sitting the past year and it may have been low on refrigerant before that I believe it was blowing cold last summer..Once I get the electrical end working, I will dig into the refrigerant side. I may just need to do a good evacuate and charge of the system. It is possible that it may have gotten damaged when I was off road . time will tell!!

 

If you have access to presureized nitrogen, CO2 or some inert gas, you could put some in to a certain pressure, watch it for a few days to see if it holds or leaks down. Helium is the best since it has a small atomic size next to hydrogen(not recommended). So it's likely to leak out the fastest ..faster than Freon. Once pressurized, spray the joints with soapy water and look for bubbles. A sizeable leak would show bubbles.

As for oil, you shouldn't need any new oil unless you replace a major component. Even then you can drain the oil out of, say, a condenser into a cup and reuse the oil as long as it's clean, or add the same amount of new oil the exact same type (which might be hard to know what it is). Don't add more oil unless you need. If you see wetness at a joint, like say a bad O-ring that's not enough to make a difference.

Just curious if you did circuit checks to see if you were getting voltage to the compressor clutch? If you apply 12v to the clutch you should hear it engage.

 

I found it strange that pressing the button on the dash doesn't give me a light at the button, and according to the list, AC and wipers share the same fuse. I assume I am not getting voltage at the clutch, but I still should see some pressure in the system. even without the clutch/compressor working.

I can also put my vacuum pump on for a while and see if it holds. That work thing keeps getting in the way of me doing much.