RangeRovers.net Forum banner

1 - 20 of 20 Posts

·
Premium Member
Joined
·
425 Posts
Discussion Starter #1
Marty has kindly supplied to HEVAC which after a loooong holiday in customs finally arrived today. Sigh.

So I happily connected the new HEVAC and still no luck. No airco. Argh. Let be known that it old one had next to 0 display and a broken fan knob. it was an early version and was replaced by a late one.
The compressor works perfectly if you connect it by hand. there is enough pressure and it really cools fine. But somehow neither the old nor the new hevac feels like sending orders to the compressor.

What am I getting wrong?
My fuse box does not have relay 3 at the moent, it does not seem to be connectd. Guess I could use an external one if need be.

temperature says 10ºC now.. that is highly unlikely and I am sure it has not happened since recorded history. that was right before according to faultmate.

I have sometimes airco grant, sometimes not. I have simulated it by grounding the respective wires.
Still zilch.

What am I overlooking?

thank you
 

·
Registered
Joined
·
1,418 Posts
Which temperature says 10deg? Outside perhaps?
With the new style controller, The system will not update the outside temp until the vehicle is moving so as not to read stagnate hot air under the truck.
If indeed this controller came from Marty in the UK, it is conceivable that was the last temp it saw. Try driving a bit?
Aside from that, you can check the plug for the temp sensor as this can get corrosion, and provide false information.
As for relay 3. Without looking in Rave, I would say, if it has a snowflake symbol on the lid of the fuse box, you will want it installed.
Beyond that, have you confirmed that the trinary switch is working, and it's plug connections are clean and tight?
 

·
Premium Member
Joined
·
425 Posts
Discussion Starter #3
Some extra information.. the hevac thinks that the grant is on. but still no compressor. Blend motors are all over the place, but I can set them via faultmate. if I put them to 10% they obey. 0% they won't have..

I am probably blind bu caan't see the pressure switch in the inputs. It is pretty impossible to access the compressor itself without dismantling a lot so I went to C166D and got immediately cold air bridging it to battery.
 

·
Premium Member
Joined
·
425 Posts
Discussion Starter #5
10º outside would be a first here trust me. I think it is only on top of the highest peak at 3500m that they have ever recorded 5ºC .
I suppose you have a point about the trinary switch bu how do I test the little thing? I can see it should send 12 V to the compressor but that depends on the input or am I mistaken?
 

·
Premium Member
Joined
·
425 Posts
Discussion Starter #6
Sorry it doesn't let me edit my last post..
OK checked input to trinary switch, no 7 BY on C102 and it also is @ 0.3 V. Now if there is nothing coming in, that is the HEVAC not switching the output ? Seems weird to me because if I provide 12 V to the compressor everything works fine, core temperature does as it is told and the whole system works a treat. There must be a way to convince the HEVAC to do what I do by hand.
 

·
Registered
Joined
·
435 Posts
have you checked the air gap on clutch 16 thou min about .3mil .8mil max If this is not right it will not stay in
 

·
Registered
Joined
·
1,478 Posts
You can't test the operation of the trinary switch as it is in line with the compressor. You would get the book symbol and a compressor circuit fail fault on an old controller as it will detect that current isn't being drawn. As the later one is intended to switch a relay, they the current sensing isn't enabled. When AC grant is on, then you should have 12v arriving at the trinary switch and, assuming that is OK and the system has enough pressure in it, that 12v should also be present at the compressor.
 

·
Registered
Joined
·
1,418 Posts
Have you tried driving it to eliminate the possibility it still thinks it is in 10 deg UK?
If it has that logged in memory, it is possible it will not run the compressor as it thinks it is cold outside.
Try a quick drive and see if it registers a realistic outside air temp?
 

·
Premium Member
Joined
·
425 Posts
Discussion Starter #10
Bolt thank you
it sounds weird butt it is a P38 :) you have a point. Do I need to relocate the sensor.. I saw something about the sensor needing to be modified.
 

·
Premium Member
Joined
·
425 Posts
Discussion Starter #11
Richard I think you gave me a good idea. If it is supposed to switch a relay the voltage might be low. will dig out the newer wiring diagram and look at the differences
 

·
LEGACY VENDOR
Joined
·
4,159 Posts
The newer HEVAC units will do as Bolt mentioned - and they will hold the last temperature until it's been driven (it will detect road speed from the ABS) and then update to the current temp.

The AC should still cut in if the HEVAC is set to 'LO'

What temperature does the Evaporator Temp sensor report? If this is faulty or has a bad connection, and is reading less than about 4 degrees, then the AC won't come on - it will switch itself off to prevent icing up of the evaporator.

If it gets cold when 12V manually connected to the compressor then it has to be something electrical.

If you get AC grant from the engine ECU, then the next place to look is RHF footwell connectors, as the feed from the HEVAC to the AC compressor goes through one of those connectors - which are known to corrode and have problems. See if you have 12v there on the correct wire (C102/202, Pin - Black/Yellow wire). If you do have 12V there, then you can unplug the trinary switch and check there for 12V on the Black/Yellow wire too. If you don't have 12V there then there's either a bad connection or break in the wire. I have found on one P38 there was actually a break in the Black/Yellow wire in front of the radiator in the loom there. I only found it as I knew I was getting 12V to the footwell connector, so probed the wire in a few places and found it in the loom at one side of the radiator, but not the other.

If you get 12V there, then try jumping pins 1 and 2 of connector at the tri pressure switch. Black/Yellow to White/Light Green. If your compressor starts, then chances are the trinary switch is toast. If the compressor still doesn't start, then it could be wear in the clutch and the HEVAC transistor not being able to give enough of a zap to get it to engage (which was the issues the earlier ones had)

The newer HEVAC units - whilst not programmed to throw the fault if the compressor doesn't come on, like the older ones did, still has the same drive transistor (think it's a MOSFET like the BECM uses for the lights etc). If this isn't powering the compressor clutch, then you should be able to break into the Black/Yellow wire, and run the feed from the HEVAC to one side of a relay coil. Ground the other side of the coil, and then run a 12V fused feed from the battery to the common contact, and then connect other side of the Black/Yellow wire to the Normally Open contact.

This will then wire the compressor so it gets it's feed directly from the battery power source, like the later vehicles do. Being a later HEVAC unit, it won't need a load resistor on it like the earlier HEVAC's did (as they had the load sensing to tell if the compressor was running or not, so had to be spoofed when the low current draw of a relay was the only thing connected).

They mention about having to change the location of the ambient air temp sensor on earlier vehicles with later HEVAC controller, but I don't think it's crucial. The sensor itself as far as I know is still the same when it comes to the resistance range it operates across, so the reading should still be somewhat correct once the HEVAC has updated itself.

One other way of possibly getting it to update the temperature... disconnect the ambient sensor, and then power it up... It might recognise the lack of connection and then show it as -40. plug sensor back in, power off/on HEVAC, clear the fault code for faulty sensor, power off/on again and it should update.

Hope this helps,

Regards,
Marty
 

·
Premium Member
Joined
·
425 Posts
Discussion Starter #13
Dear Marty, Bolt and Richard.
1- You were all right about HEVACs taking time to adapt to our climate.
I moved the car in and out of the garage and it is now right.
hevac.jpg

but it definitely does not send 12V on pin 7 of c244. As I said above, I couldn't find it on c102 either.

If I understand the trinary switch right it opens if he pressure is wrong? so it should get a permanent supply via the Hevac.

Now I am absolutely lost why the HEVAC does not send 12V???
 

·
Premium Member
Joined
·
425 Posts
Discussion Starter #14
Resolved, many thanks to all. :smile:
The specialist who topped up the aircon and wondrred how to make the compressor work with the old HEVAC bent a pin on the pressure switch .
Also they managed to do this to C244 and it didn't show as it was inside the plug, only saw it when I opened the plastic latches.

thanks to the idiots who installed the radio. :shock:. They had used the Hevac as a supply
View attachment 264305
 

·
Premium Member
Joined
·
425 Posts
Discussion Starter #16
<img src="http://www.rangerovers.net/forum/images/smilies/icon_biggrin.gif" border="0" alt="" title="" class="inlineimg" /> Good news - and glad it's all working properly now!
Thank You Marry

Here is the best bit.. the temperature sensor decided in the morning to check the local environment and when I was starting to retrieve a blend motor (flap is stuck) and observed things life it said.. oh it is afternoon here, I am not in Britain and fast asleep. So it got to a realistic 34°c and has worked ever since.

Now I have only left to do the blend flap and work out why the BECM thinks fuse 4 is blown and doesn't want to go out of low.
And this will be the back of the worst p38 ever
 

·
Registered
Joined
·
755 Posts
Gotta love people that think they can grab a live from wherever they want to power something,,
can make faults like this a nightmare because they’re lazy.
 

·
Registered
Joined
·
1,418 Posts
Finally! success!!
Out of curiosity, did the "Pro" bend the pin to test, and forget to bend it back, or was he just ham fisted with the connector?
 

·
Premium Member
Joined
·
425 Posts
Discussion Starter #19
Finally! success!!
Out of curiosity, did the "Pro" bend the pin to test, and forget to bend it back, or was he just ham fisted with the connector?
I love the expression ham fisted 😊.
Yes that describes it best. Started to be quite afraid of him after I realised that handling a multimeter was being his skills. And this is a supposedly trained technician.

Well I make mistakes, too.
Specially for you the lovely wire.
Had to fiddle pin out of a Toyota plug to repair this. Can't buy anything here.
 

Attachments

·
Premium Member
Joined
·
425 Posts
Discussion Starter #20
Sorry am too dump to upload an image on my phone.. somebody may tell me please and if you like smuggle it into the last post

that was hiding in the Hevac pug, airoc clutch output

wire broken.jpg
 
1 - 20 of 20 Posts
Top