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What diagnostics (apart from Nano and Testbook) can I use to read/reset HEVAC codes?
I've got the booksymbol since two days and can't think of any cause.

  • if I manually set the functions (contact on-engine off) I can hear the blendmotors for a couple of seconds and then stop, no clicking of missing sprocket-teeth.
  • The a/c has a leaky drier but still kicks in now and then, past winter I had a leaky condenser, that did not give a booksymbol. Switching a/c off makes no difference, book stays.

So I need a codereader that can reset HEVAC too, I'm not in the market for a Nano unless the lotteryman comes at the door.
Tony.

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Hi Tony
Have you had a look at the Symptoms & Diagnosis section here?
Re the Diagnostics stuff, the only other software that can access HEVAC (among many other systems) that I know of is the paid version of EASUnlock (V4) which is cheaper than Nano etc
The fault symbol does clear once the fault is fixed though so no software required to clear it.
EDIT this post seems to have a fair list of diagnostics processes you can do manually

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Thanks Mark, the repair section I already had a quick look at, I'll dig into the diagnosis-section.
As for EAS-V4 is a good idea, if it does what it says that should be:

Working Diagnostic Sub-Systems
         Air Suspension - Read & Clear Faults
         Air Suspension - Calibrate Air Suspension
         Air Suspension - Air Suspension
         Air Suspension - Function Tests
         Air Suspension - Live Sensor Readings
         Body Control Module - Customize Factory Settings
         Body Control Module - Function Tests
         Body Control Module - Live Sensor Readings
         GEMs Engine - Read & Clear Faults
         GEMs Engine - Relearn immobilizer Codes
         GEMs Engine - Reset Adaptive Fuel Values
         Motronic Engine - Read & Clear Faults
         Motronic Engine - Reset Adaptive Fuel Values
         HEVAC - Read & Clear Faults
         HEVAC - Read & Function Tests
         ABS Early- Read & Clear Faults
         ABS Late- Read & Clear Faults

I already use the V3 version so have the cable, in fact I don't need more...

Thanks for the tip!

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Saw your edit: this is very helpful for the moment, I'll check that!
Thanks.

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If you get really stuck Tony and fancy an evening out, I'll be in Calais on Monday evening. My ferry home isn't until 20.35 but I can get there earlier if needed (and the Nanocom is in the car).

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That is a very generous offer Richard, I'll PM you tomorrow if I can make it.
Our son decided this afternoon to buy a Merc as his daily driver but there has some work to be done on it.
I will discuss it tomorrow and be back asap.
Thanks again!
Tony.

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First investigation so far is the starbordside of the cabin stays cold. When toggling the tempswitch up and down the temp stays cold.
So that's a stuck flap or a dodgy motor...
Tony.

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i have a set of blend motors that you can have. I'll be honest and say i dunno if they work or not. They came with a load of spares when i got my first p38 and i can't remember what the bloke said. I'm inclined to say they'd work as why would anyone keep ones that don't.

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I've got a box of dodgy ones... that one day I hope I have the time to sit down and recondition, and with any luck get working again to go back into another RR!

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Well finally have the time and peace to get on with the rightside blendmotor, plus I get a 'server down' error from ImgSave so had to look for another hostprovider to show pics. Let's see if it works.

Took it off the heaterbox (that topscrew took me... well you don't wanna know) and opened it.
Looks all pretty good inside, no missing teeth or broken solderjoints. The potmeter I can't say, have to measure resistance.
enter image description here
enter image description here
If I switch ign on the worm sometimes does a few turns and stops, makes no difference if I change temp or not.
Is this ok or not?
And yes plasticsoulman, I'd be very happy with yours and pay the postage, thank you for the offer.

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The flap moves free without any sticking.
I wonder, the lever has a hole in it, is this a fore-seeing service from LR in case you want it manually by cable?
enter image description here

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What can often happen is that the motor starts to gum up so moves slowly. So when it does the self test it doesn't reach the end of the travel soon enough so the HEVAC declares it faulty and no longer tries to move it. A squirt of contact cleaner into the motor and working it back and forth from a 12V supply is often enough to sort it out for at least a couple of years.

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Also, if the potentiometer is faulty, the hevac will try moving it in both directions to see if it gets a change in reading - if not, then it will flag it up as faulty and not use it anymore...

Potentiometer can be tested with multimeter - you should have about 10K ohms between Grey and Red/Black - and then varying between 0Ohms, and 10K between Grey and White, and the inverse of it (10K down to 0Ohms) between Grey and Red/Black (depending on which multimeter probe you put on which colour with determine direction of the change for each pair of wires, but you get my drift!).

You should get an even, linear change in resistance, any spikes or dropouts indicate problems on the resistive track

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The plastic casing says 7V so I took this 6V blockbattery I have and put it direct to the motor in/output and it turns both ways!
Not speedy but it turns, gave it a squirt of contactcleaner (I can see little sparks from the brushes) and put it all together.
Now the shaft moves just a bit and then it stops (together with a relay-click in RH footwell but maybe a coincidence), mayby it is because it has no signal from the heaterbox sensor (cold engine).
I'll put it all together and see what happens.

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Chequebook is off! Job done (for now).
Now getting the ducts in again, well there is a tape for that, it's called ducttape!
Thanks for your input guys, blueplasticsoulman in particular for your offer.
enter image description here

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Nice one. I replaced my drivers blend motor a few years ago because it would stick at one extreme or the other, invariably at hot in the summer and cold in the winter (driving over the Massif Centrale in a blizzard with the outside temperature showing -3 while sitting inside a sleeping bag so my feet didn't freeze convinced me I really had to do something about it). After changing it and sorting the problem I tested the one I'd removed and found all it needed was a clean so at least I've got a spare now.

Yes, sealing the joints in the ducts is, I think, the only time I have ever used duct tape for it's intended purpose.....

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Dear All,
Not really a resurrection, a quick question that has no obvious home and not wanting to start a brand new thread. I may need to run mine without the HEVAC control unit plugged in for a few days, that shouldn't cause any problems other than a cold cabin? No BECM issues?

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Two of the contributers are sadly no longer with us I am afraid. Orangebean and Ferryman RIP.

I don't know for sure if you can run the car with it disconnected. It would throw up a load of errors at least.

I did think about buying the manual HEVAC version as something handy to have in "just in case".

Here is one on Ebay:
https://www.ebay.co.uk/itm/RANGE-ROVER-P38-1994-1998-HEATER-CONTROL-PANEL-Manual-Hevac/303711654702?hash=item46b6a0132e:g:u8UAAOSwxaNeDahQ

It is too much.They normally go for just £20 or so.

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Shouldn't be a problem if all the plugs are undone (which they will be if you are going to take the HEVAC unit out completely). If you set it at hot on both sides then pull the HEVAC, the blend motors will have driven the flaps to give maximum airflow through the matrix and they will stay there. You won't have any blowers working but ram air should still give you some heat when moving.

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Perhaps I could join in on this post too.
Having got the Nanocom connected and working - thank you Richard, I have a fine selection of error messages but concentrating on the HEVAC I've got 40. A/C request line fault - current, and 55 Distribution door motor stalled -current.
So following other posts I've removed the motor and duct and sprayed liberally with silicone spray and moved the flaps manually and the only issue is a slight overcentre feeling on the last couple of teeth on the quafrant. Even after a good waggle too and fro the 55 message is still coming on.
Any suggestions on the next step?