Hi Guys,

thanks for replies.

Some communication wires somehow got crossed here though.
I can't seem to say it clearly enough 😀
There is NOTHING wrong with the compressor in my P38.
IT WORKS WORKS WORKS perfectly.
Nothing wrong with it.

I don't know how this topic got side tracked on a non existent fault,
so thought I'd better remake the point.

The only reason the compressor was not functioning ( on the hot days )
was that it was no longer being ASKED TO FUNCTION by the HEVAC.
As said I have LED indicators on my dash to show me what the HEVAC
is asking for. That's how I know. 😀

cheers,
Paul.

Hi Gilbert,

• when working before it was reasonably cool but not as cool as now. Especially when condenser fans on.
• I do not get test book from failing compressor clutch, this is not a problem, ie working.
• HEVAC signalling ECM for compressor clutch is a different signal to the condenser fan comms to the ECM.

Working beautifully now but I'd like to test in in a 35+ day.
Only a few weeks of summer left and we have El nino this year and the summer is mild.
If it was El nina we'd be getting our fair share of 40 or 42+ days.
Happy for El Nino. 😁 Making the most of it...

Regards,
Paul.

Hi Guys!

sorry for late reply. Been busy, including working on the Rangie.

Ok been to the mechanic. The thermometers on the diagnostics ALL look ok. I have a pic for you but can't post it here for some reason. Won't let me.
He did the whole re gas procedure. Properly. (recover, pressure test, vac out, refill) It had about 390 something in there and should have had 1200 according to him. So needed a REGAS. Still can't see why a total shutdown of the AC occurred in 35 degree day, but maybe low gas was to blame. Maybe the HEVAC got jack of trying to cool the interior when it was so hard with little GAS.

I tried to test it Sunday but it only got to 30 degrees. So 1 hours drive in 30 degrees is probably not hot enough to see if the original fault is fixed. It used to work on 30 degrees on low gas but 35+ would normally mean "pack it in". I'm hoping that the REGAS will be all that is required to keep it running on super hot days.

However, Sloth made an interesting comment about first start up on a hot day. The rangie will try to quickly cool the interior by turning on the condenser fans.
I normally only get the test book symbol on these hot days , a few minutes after start up and I never notice my condenser fans going.
Hmmmmmmm !

I was keen to diagnose my fans. I tested all fuses and relays. All good. Then I removed RL18 and shorted the switch holes. Both fans worked! I tested the output of the ECM and it was hi. ie +12V which will keep RL18 OFF. I checked the input to the ECM and it was also high +12V. The only stuff on the input to the ECM is the press switch 1 and the HEVAC. I checked the HEVAC and it's line was 0v. Obviously pressure switch was open. But where was the +12V coming from? It could have been from the un loaded coil of RL18. So I pulled out R18 and the +12v was still there. So it is coming from the ECM. More importantly it's coming out of BOTH sides of the ECM. Input and Output. Which is interesting because it means the ECM is actually signalling the HEVAC. You would think it's the other way around. PS the diesel P38 wires directly from the HEVAC to RL18 but the petrol P38 goes via the ECM. I then bypassed the single pressure switch and put that +12v from the ECM to the HEVAC and straight away the HEVAC found some sink for that and the input to the ECM went to 0v and the fans came on. I think that HEVAC senses briefly that 12V from the ECM before it brings it low. That way the HEVAC KNOWS that the pressure switch has closed. On very hot days it expects it to close and if it doesn't briefly see the +12v from the ECM it lights the testbook. Not wanting to have to convince the mechanic to replace the press switch and also not necessarily wanting to pay for that I put a new "pressure" switch in my dash board. ;) . Now I can start my condenser fans when I want. Yesterday was about 25 degrees. Not that hot I know, but I went for a drive and switched on the fans. 1/2 hour later still no test book and very cool interior.

Could consider doing something similar for the press switch 2 which sends the fans to parallel and fast mode. But no rush.

Regards,
Paul.

Thanks GilbertD.

Makes sense to me.
The mechanic just wants to blindly re gas as a first step.
sigh...
Hopefully he intends to check with the diagnostics.

Look, the signal from the HEVAC does go further than the pressure switch and the AC works reasonably 90% of the time.
On HOT days the signal does not come from the HEVAC. That is the problem.

ps I like after 3 rangies you have: "96 4.6HSE Ascot because you never know when you might need a spare" 😀
I agree. You can never have enough rangies 😉

Paul.

Hi Sloth, and All,

thanks for your replies. Much appreciated.

The LED is wired at connector C202 C102, pin 7. It's behind the kick board RHS footwell. It's electrically between the HEVAC and the dual pressure switch. And then subsequently the compressor. I put the LED in the dash so I can see it go on when the HEVAC requests the compressor to turn on. It stopped going on when it was quite hot on a long trip. Yes I am in Australia, although it was not one of our scorchers, it was only about 34 celsius. The outdoor ambient temp sensor reads quite accurately BTW.

The problem is not the clutch as that would still show the LED lighting up. I fixed that one several years back and installed the LED to help with that problem at the time.

I noticed yesterday that of the 2 coolant lines in the engine bay, none of them are suitably COLD.
This is days after the hot day trip when the AC is working again as it's not under heat stress. Compressor going no problem.

Without a really cold coolant line I suspect that the coolant needs a re fill.

From other things I read on the forums I suspect that the EVAP temp sensor may be reading that the AC is VERY ineffective due to low coolant and the HEVAC is NOT HAPPY and is withdrawing the compressor signal.
Sloth said "The evap sensor is used constantly to cycle the system - not just for icing. "
I'm suspecting that poor temp readings by the evap sensor due to other faults ( eg low coolant ) might be able to shutdown the AC.
Does this sound plausible to others?

RE GAS, top up, is booked for Friday.
Sunday is meant to be 36 degrees and nice and hot enough to go for a drive and test it.

Cheers,
Paul.

Hi All,

my P38 1995 Air Con works fine as long as it's not a really hot day.
Hot days it fails.

My good Man at the garage ( with good Range Rover experience ) suggests re gassing. My A/C does have weaker cold than it should be when working. Can low gas stop a working A/C when it gets too hot?

Also, I have an LED light on the output of the HEVAC to tell me when the HEVAC sends the signal to the DUAL pressure switch to run the compressor and this LED light does not come on when the A/C is failing in hot weather. As far as I can read in the ETM the only thing that might stop this signal from the HEVAC is the Evap Temp Sensor , sensing ice on the evaporator. I gather if this sensor is faulty it could stop the A/C working. What do you think?

I'm not sure that I have ever seen my condenser fans run. If there is a fault here can this stop the HEVAC from sending the signal to start the compressor? What do you think?

RR Brains trust can you please come to my rescue 😀

cheers,
Paul.

Hi,

When it comes to fixing a driver pack for the EAS,
is there any info on the net on details?
I read here Marty fixed one.

thanks Paul.
PS I've just had the pressure signal constantly high message.