So I've only got 9.45 volts to the air con compressor when switched on and off. It's had a regas although halfords said I had gas in there and they tried to refill and they couldnt refill it for some reason any thoughts??[/url]

Last edited by William97841 on 29th Jun 2015 10:14pm. Edited 1 time in total

Is the compressor clutch kicking in and out?
Get someone to switch the AC button on and off while listening under the bonnet.
I would have thought 9.45V was too low, online guides suggest generally it needs to be 10.5V minimum for the clutch to kick in properly.
Failure of the compressor to kick in might explain why it couldn't be recharged.

I would check the voltage being supplied to the clutch with it disconnected. That will point the direction to go, if around 12V with the AC switch on (and blower active) then it points to a clutch issue (wiring downstream or field coil), if still 9.45v then wiring upstream or supply issue.
What's the battery voltage with the engine idling and under load (lights on etc.)?

I have pretty much exactly the same problem at the moment - the red and blue wire supplying the clutch is getting 9.2 volts constantly, ignition off or on, ac button off or on. This caused my compressor clutch to burn out.

I have had the compressor remanufactured and if I apply 12v the clutch engages so I know that is working. I have traced wires and they are all good up to the switch. If you remove the ac switch panel (very simple and there is a good powerful uk video on YouTube) you will find the ac condensor wires on the three pin black connector. On this connector you should have earth, 12v feed and compressor feed. When I bridge the 12v and feed wires my compressor clutch engages and with this connector removed from the switch panel the constant 9v disappears. This has led me to believe I have a fault in the switch panel. I have a replacement used unit on the way and will report back if it fixes.

I would wager from your description that you problem may be the same, and if you pull out the switch panel it should be easy to check.

The compressor clutch is fed from the Hevac ecu which is located behind the centre consol.
If you can't resolve the matter you may wish to check the voltage at connector C1630 which connects the compressor clutch onto the ecu.

As noted above, that is the 3 pin black connector I was on about.

^
We posted at the same time, great minds etc.

2001 L322 Circuit Diagrams can be downloaded here:
http://www.legionlandrover.com/manuales/el...001%29.pdf

Page 110 shows the HEVAC system.

A constant 9.45V does suggest a faulty HEVAC unit, possibly a blown driver on that circuit.

Thank you guys for the response gonna test it tonight I'll keep you updated

I tested the black while on the hevac unit I got 14v on the red and blue cable 0.025mv on the black cable on the black plug. At the end of the connector to the compressor while linked the red and black cable I then get 14v to the compressor. So I know the compressor has gone. It's just weird that I those reading on the plug at the back of the unit. I don't get 9.45 at the black plug on the hevac only at the connector to the compressor

Is that right?

It is the black (with grey strip I think) that links to the compressor clutch, the red and blue wire looks to feed power into the HVAC ecu/switch unit despite looking like the same wire at the compressor end. If you use a spare wire to bridge the red and black wires at the HVAC ecu end (with it unplugged) do you get 12v at the compressor and thus an engaged clutch?

Yep I've bridged the red and blue cable to the black cable and got 14v to the compressor sadly compressor didn't kick or engage so I'm guessing I have the same problem as you kezbo1981 lol. So I think it's gonna need both hvac ecu and compressor. Because when I did disconnect that black plug the 9.45 v dropped out reconnected and 9.45v back so that's gone by the sounds of things.

Is the compressor hard to change?

When you say 14v I assume you had the engine running at the time?

Changing the compressor isnt difficult. Mine is on a 4.2 SC but I would have thought yours would be similar. To start with you are cracking into the AC system so really the refrigerant gas needs to be removed from the system into a gas cylinder (need an ac specialist for this), if your gas has already leaked over the years then not a problem. The there are two gas pipes onto the compressor these are secured with one bolt each. You then need to remove the drive belt by releasing the tensioner (mine involves pulling it with a 3/8 drive ratchet). The compressor can then be removed, mine has 3 10mm bolts holding it to the block, two long one short. Access was the most difficult part for me, working around the v8, there may be more room on yours I dont know.

As for getting a replacement compressor, I looked at all the usual suspects and for a decent brand the cheapest I found was £460. You could get a second hand unit but I didnt like that idea as you dont know if it will work and if so for how long. I found a company local to me (compressortech.co.uk) who re manufacture the compressors and they turned mine around in two days for £234.

Yeah sorry I had the car running because I wanted to see what voltage I was getting. Well I have the l322 td6 and I know I've gotta remove the bottom tray but I know the access is tight...so it looks like a fun job lol. Well £234 does sound appealing so might have to do that.

Have you got your panel yet kezbo and your air con up and running now with the new panel and compressor?

My new (used) HVAC ecu panel arrived today and..... same problem. Now I am confused as I may have bought a dodgy replacement panel or it might be another issue. However given everything is fine with the panel disconnected and with it connected I'm getting a constant 9v to the compressor I'm still of the opinion that the panel must be at fault. I need to do some more investigation, in the mean time if anyone else has any ideas please let me know!

The other possibility is there's an issue with the clutch field coil, either short/open circuit or incorrect resistance (although if you've tried 12V directly to it and it's clicking in it's unlikely to be a problem).
Try measuring the resistance of the clutch coil (with it unplugged), it should measure a few ohms between the coil input and earth (roughly 3 to 5 ohms), anything wildly outside that then there's a problem.
Looking on the net at other A/C systems, the output of the HEVAC can be 9-9.5V WITHOUT LOAD due to the semiconductor drivers used. You need to measure the voltage of the circuit with everything connected and running, i.e. backprobe the connector or pierce the insulation. If you are still measuring around 9.5V then it does suggest there is an open circuit somewhere OR the HEVAC is not actually commanding the clutch to operate. In which case it suggests an issue elsewhere with the A/C (low/high pressure sensor, Evaporator temperature sensor, Ambient air temperature sensor etc.).

Here's an example A/C troubleshooting guide for an Audi A4 (it mentions the 9-9.5V on the clutch line). Yes it's a different system but the principles are still the same.
http://pics.tdiclub.com/data/517/A4_Air_Co..._Rev_7.pdf

The L322 Electrical Library manual does describe how the A/C system works (page 4.56 onwards).