Strange HEVAC issue with MY 09/1995 P38 Range Rover

[davus]

Howdy all,


Newbie to the forum, so go gently :).


My name is Dave, and just yesterday I bought my first range rover purely as a tow vehicle for my boat. Its a really clean car inside and out, and has been well looked after. It has 240 click on the clock, and for the best part is completely stock, and really quite unmolested. Its a little different to drive to my HSV Senator......but then again the senator cant tow for its life! :)


I have a strange problem with the HEVAC system, which I understand (through a lot of research last night and today), is a pretty common issue with these cars.


I've had a search through various forums on various websites, and have tried a few things, but nothing thus far has worked. I have also searched this forum, finding similar issues, but nothing matching.


The problem!:


My HEVAC indeed has the beloved book with exclamation mark.


1) The air conditioning works. IE the compressor clicks in and out, and cold air certainly blows out.......but only out of the passenger side. Even if I turn the temp control on the drivers side right down to LOW - it only blows out warm air.


2) The amount of air coming out seems to be very low to me, even if I turn the fan control up to its highest setting. In addition to this, I have removed the pollen filters on both the drivers and passenger side, and has confirmed that on the PASSENGER side blower fan is working (I can see it spinning if I look in through the pollen filter opening).


3) When I change the air direction with the controls (IE windscreen, feet, face etc), nothing seems to change.


So, they are the initial problems. And here is a little more information........


Following recommendations from a few various forums, I inspected the fuse box, and found that the RL-7 position was cracked and melted...which I believe is a common thing. In fact, with the HEVAC fan blowing, if I wiggled RL-7 the passenger fan would cut in and out.


I worked out that RL-7 is the passenger fan, and RL-6 is the drivers fan.


Even though the fuse box seemed damaged in the passenger fan relay position, I pulled it out all the same and gave it a once over. I separated the two fuse boards inside the box, resoldered all the dry joints. Repaired the dodgy RL-7 relay seat and put it back together. Whilst this did NOT solve the drivers fan issue, no other problems arose after this.


One other strange this is that as we were driving along yesterday with the "air con" going, we hit a bump in the road, and hey presto!.......the air coming out of the vents sprang to life...gale force 12!. So we turned it down a little, and that seemed to make it revert back to poor operation.


So - as far as I can see it, I have s number of problems I need to attend to.


1) The fact that I have only warm air coming out of the drivers side
2) The fact that as I change where the air should be coming out, it makes no difference.
3) The fact that the drivers fan doesn't appear to be working. (which confuses me a little given that there is air coming out of the drivers side.........its just warm - and VERY low volume).


From what ive read, it appears as though I need to focus on servo motors?.....but does anyone have any hints or tips?


Obviously I can start pulling the dahs apart and start checking physical fans etc, but if there are some other shortcut ways first, id love to try them.


I stumbled across this post on another site ---> Range Rover P38 Maintenance repair improvements and tips learned by experience by ownership. (http://www.stockholmviews.com/p38/index.html#hevac) which seemed to indicate there is a way of testing the servo motors by bridging pins behind the hevac controller...... but its a little unclear. Has anyone else tried this approach?


Thanks to anyone who can provide any guidance or assistance.


Apologies to anyone who reads this twice. I have cross posted on another forum to increase the exposure and chance of some broader help.


Regards


Dave

[davidsonsm]

Definitely sounds like the blend motors need changing, at least the distribution and the RHS blend one. Most on here have experience of doing the change and new ones are generally recommended. There are several different ways of tackling the problem and I bet a few could now do the job in half a day. It does involve the partial disassembly of the dash. To avoid taking out the whole dash, involves cutting the plastic ductwork. Pretty sure the rangerover.net website instructions were the ones I followed.

I'll try to post the link to the instructions.

[daf11e]

"RANGE ROVER BLEND MOTOR REPAIR ON A P38 a how to guide"
Just put this search in at rangeovernet and you will see a step by step guide on the blend motor replacement. And as said by davodsonsm I would suggest new replacements.......It is a lot easier to follow than trying to explain in one post.........good luck and welcome!

[blindin]

Hi there.
It defiantly sounds like the blend motors aren't doing what they should do.
One other thing to think about may be the flap is stuck. This is quite common too. The lack of air could be the direction flap stuck between them all, and therefore the volume of air is coming out, just in all directions. You may even find that it has a cut duct and is just blasting out the air behind the dash. The temperature control could also be a sticky flap. I would strongly recommend getting yourself a nanocom or similar to pin point the fault first. I have managed to remove the rhs blend temp motor with out cutting, or removing the duct, but in all fairness, it was a struggle, and my temper was getting very thin within half hour. To get the blend motors to move, you force them power from the back of the hevac unit, you need to partially remove the center console stuff so you can then undo the 4 screws holding the hevac in, then you can unclip the wires, and then put power to them. You'll also need to work out which wires to do. My fault at the moment is that the potentiometer is not working, so the car does not know where the flap is sitting.
Good luck with it, you will find it testing!

[Hoges]

Hi Dave...and welcome to the forum:D I am sure you will be well supported...you have done your homework and sussed out quite a lot! Most impressed with your fuse box efforts...(we like that!!;) )

There's another well known issue with the (plastic) heater plenum "box"...it can become distorted due to high summer cabin temps. This can cause the moving flaps to bind thereby straining the blend motors and causing them to seize. Hence the $Book mark. The sudden increase in air flow after the "bump" may well have been caused by a flap being jolted past its 'seize' point...

would be well worth your while also checking the status of the pollen filters. There's a heap of info on these in rangerovers.net. This is a 5 minute job. clogged pollen filters also are responsible for fans working overtime...

Good luck with it.. keep asking questions!

[davus]

Thanks very much guys. Great support!

I have been considering looking into some sort of diagnostic tool to try and help identify the source. Would one of these tools (black box?) help?

There seems tone a number of generic odbII diagnostic tools around, but from what I can tell the vehicle must be odbII compliant. I can't seem to find any documentation confirming if a 4.6 petrol 1995 p38 is compliant or not.

Would you guys recommend sourcing one of these tools?. If so, which would be a good cost effective option allowing me to read and clear codes?

Thanks again.

Dave

[mtb_gary]

Dave

Welcome aboard. With respect to diagnostics, I have the Bluetooth Torque Pro app on my Android phone, it is easy to use but is limited in what it can read with respect to p38 specific information eg EAS. I also have the Faultmate FCR (Fault Code Reader) this useful little device lives in my centre console. It will read any faults and let you know what they are plus you can also clear the faults. What it does not do however is let you adjust any of the parameters. In hindsight, I wish I had paid the extra money for the next model that also lets you recalibrate and access the testing modes. A diagnostic tool that is only fairly new to the market is the RSW Solutions software. The RSW EAS software has been around now for quite some time and is widely available in its early incarnation as a free download. You will however require a laptop and a dedicated OBD2 interface cable. The new version gets access to a lot more of the p38 specific codes. I'm pretty sure there is someone on this forum with the latest RSW diagnostic software that may be able to give a first hand update on how well it performs.

Gary

[davus]

Thanks very much Gary. Are you sure the RSW Software is compatible with the P38?. I had a read of their website and it doesn't seem to specify that it does (unless of course im missing it).


Back on the topic of my blend motors, I did a little more mucking around this afternoon, and I wonder if I've misdiagnosed some of it.


On further investigation, when I press the different buttons to redirect the air, it does seem to work, however it seems to be quite slow. IE: If it is coming out on the face, and I swap it to windscreen, it will take about 4-5 seconds to actually swap the air. Im used to modern cars doing it almost instantly, so im wondering if I am just expecting it to be quicker than it actually is? Does this time sound about right?


I think perhaps I was getting a little mislead by the fact that the air volume seems to be very low (I assume because the drivers side blower fan is not working.)


So....my task list so far is this (in relative order of ease)


For Blend Motors:
1) Disconnect the HEVAC plugs on the rear of the controller to clear the Book and exclamation mark to see if the motors start working (or if the book just comes straight back)
2) Pull out the HEVAC controller and try to connect power to the blend motors independantly to see if they work.
3) Inspect the flaps to see if they are stuck. (I assume this requires some dash removal)?
4) Dependant on above tests - begin replacing blend motors.


For the Drivers Side Blower Fan
1) Ill admit im a littl estmped for ideas on this one - with the exception of standard troubleshooting / pulling it out and just inspecting / replacing it. Any other helpful pointers?


Thanks all - what a great community.


Dave

[mtb_gary]

Dave

Specifically for a p38

EAS Unlock V3 (http://www.rswsolutions.com/index.php/range-rover-p38a/range-rover-p38a-eas-unlock-v3)

Storey Wilson (the software developer) has a p38 as his own car

Gary

[davus]

Thanks Gary.

Isn't this software for the electronics airbag suspension (EAS) only?

Dave

[blindin]

Hi, I ended up pulling my dash out twice, and need to do it again as at the time I didn't have the correct cable or unlock code for the nanocom.
When I first bought my 98 gems, the heater had been disconnected, and no aircon.
The dash out first time to fit new heater matrix, then once in, it got put back together to find that it would only blow hot air.
I done the same as you, researched what problems it could be, took the dash out, took the blend motor apart and it was working.
I wish, not only had I tried to power it without removing, but secondly, used a diagnostic tool to get an idea why it was faulty.
After I had done this, it worked for a while. Now it doesn't due to faulty potentiometer.
Good luck

[mtb_gary]

Thanks Gary.

Isn't this software for the electronics airbag suspension (EAS) only?

Dave

Dave

That's where the software started.....it now does a whole lot more :cool:

Gary

[ian4002000]

Dave

That's where the software started.....it now does a whole lot more :cool:

Gary


After many repairs and dash disassembling on my P38 I would recommend hooking it up to a Nanocom or equivalent first to see what is wrong with the HEVAC system if anything.
After clearing the faults, to see if any new ones occur you can recalibrate the flaps and blend motors. this will let you know which motors are working etc. you can also power the motors separately to see if they work if the HEVAC cant. I suggest doing all this before dismantling as it will save you time and stress and money.
You also get readouts from all inputs from the HEVAC system which is great and you can know what is occurring.

[blindin]

Can't agree more Ian.
That is what I was trying to say, but a long way round. Well said!

[davus]

Thanks very much guys.


I certainly would love to get a nanocom or something similar to read and reset faults, but im just trying to keep spend to a minimum with this bad boy....after all, its just my tow car.


So, it appears as though ive ironed out most of the heater / aircon / blend motor issues.


1) I narrowed the issue with the drivers side blower not working down to the blower itself. I removed both the drivers and passenger blower motors and swapped them. Sure enough the working passenger side motor operated fine in the drivers side, and the drivers motor didn't work at all in the passenger side. A quick trip to mater motors in Thomastown, and $60 later for a second hand motor and were back in business with both fans blowing. While the fans were out I also took the opportunity to check both of the circulation motors - both working fine.


2) I narrowed the book and exclamation mark down to the blend motor controlling the drivers side heat/cool blend. The distribution servo I have confirmed as working (it just seems to take a while to actually make the change - but operates fine). The passenger side blend I have also confirmed as operational (IE: I can see it working as I change the temp button for the passenger side. Whilst at matar motors I picked up a set of second hand blend motors for $60, in the hope that one of the motors worked. I remove the dead motor and spliced in one of my "new - secondhand" ones, and we are now cooking with gas!. I have no book light on the hevac controller anymore, and all three blend motors are operational.


So now (because I didn't think ahead), I have an SRS light on my dash that I need to get cleared.


A few questions that im hoping someone may be able to help with.


Blend motor Travel Steps - Lets say for example the temp on the passenger side is on LO, and the servo motor is at one end of its rotation. As I slowly increase the temp, I would have thought that the servo would travel in a fairly linear path all the way to its hot position. However it doesn't seem to do this. As I move from say LO to 16 or so, it does move a little, but between say 16 and 27 it doesn't really move at all, and then when I hit 28 (one before HI I think?), it move almost the whole rest of the way in that one click. Is this normal?. Keep in mind as I test this, my dash is out so I have everything else (whatever cabin temp sensors etc) disconnected.


Blend Motor "Bouncing" - Another thing I have noticed is that (and I think I have my numbers correct here), if I set the temp on one side to JUST below HI, the servo motor will kindof "bounce" back and forward. Its only by about 1mm movement so its very insignificant, but I can see it all the same. Is this something anyone else has experienced?. Again it may have something to do with everything not being connected.


Video:
http://youtu.be/sLgCHxEaxRI


Distribution Motor - Is it normal to take say 1-2 second to change between air flow direction?. IE - If I swap between face and feet, it will take about 2 seconds for the servo to do its thing. Im used to my new HSV doing it in a very short time, so I could be expecting too much from a 1996 car?. Is it normal for it to travel at this speed.



Video:
http://youtu.be/tXqrpzNPooM

Thanks very much guys. Appreciate all the help and advice.


Dave

[blindin]

I have the same with the distribution. It is very slow, and almost like its not working. not sure if its normal though.
With regards to the temp:
My fault is that the blend motor will move, but it doesn't know where it is - I do have the cheque book though. Mine will go between hot and cold, but nothing in between. Have you checked that that the temperature is adjusting ok? if it is changing though ok and isn't going hot to cold, or visa versa with very little difference in between, I would say its ok, but really don't know as I haven't looked at the movement on mine. if you use a multi meter you can check that the blend motor is returning a smooth curve from the potentiometer, just check the resistance - there should be 5 wires, 2 for the motor, and 3 for the signal, 2 wires are at either end of the resistor ( potentiometer ) and one will adjust, you will be able to measure this against either of the other 2. Hope this helps, you'll need to figure out which wire is what, and the measurement you should have, as without searching I don't know what it should be reading.
Good luck, & well done

[davus]

Hi Guys,

Sorry for the late reply, been flat out with a new job (going back to work after 8 months leave is hard!).

Anyway, after the above fixes (second hand blend motors and a second hand blower fan), my problems seem to be sorted out.

The infamous book symbol has gone (for the most part), and the heater & A/C both work completely as expected.

I do have a strange issue where the book symbol comes on after about 20 minutes (sometimes), and it only seems to be if i touch the A/C ON OFF switch..........however even though it comes on, it all still seems to work fine.

I plan to get a diagnostics tool soon so i can keep an eye on this type of thing. It might have been a cheap car to tow my boat, but it does need a whole lot of TLC :)

Thanks again guys. Im off to post a question about my new problem! LOL

Dave

[Shirley]

Hey Davus,
Quite often the HEVAC becomes distorted from temperature changes during summer and winter and the flaps that direct the air to the required areas or the car cab become jammed.
Sometimes it can burn out the blend motor, strip the gears or just not operate at all. Quite often the blend motor is OK but the persistent jamming in the venturi has to be addressed. A bit of messing about but by freeing up the flaps can resolve the problem at no cost other than time and frustration...

Had the same problem - jammed flap and weak blend motor.
Replaced with one out of a Peugeot 504 (I think) Half the price, stronger unit, brass gears - Just had to cut and join the wiring loom - the colours are all the same in both cars, so not big deal.

Cheers Shirley....

[davus]

Quite often the blend motor is OK but the persistent jamming in the venturi has to be addressed.

Hi Shirley,

thanks for responding!.

Just wanting to get some clarification on the above quoted reference? What do you mean by venturi? And where are they?

Strangely now my A/C seems to be playing up. Where previously it was working well, now i seems to work well for a period of time (random) and then just isnt cold anymore. I can still hear the compressor clicking in and out so im guessing pressure is OK (i think they have a pressure switch in them?)....but for some reason the air coming out just gradually gets warmer and warmer untill it feels like just outside air temperature.

Any suggestions on that?.

I think its time to buy the EAS Unlocker v3 software....it really seems to be the "ducks guts" to help pinpointing all these little electrical gremlins these cars get.

Dave

[Hoges]

There can be a problem with the compressor actually engaging due to wear in the clutch mechanism. If you do an internal google search on this forum there is info regarding how to fix. It's a reasonably straightforward job. Search similarly on RANGEROVERS.NET HOME (http://www.rangerovers.net)

The heater box can become distorted due to intense cabin heat when parked in the summer. This can cause the blend flap to jam on hot days. I currently have this issue. No book symbol on days below 22 deg C but any hotter and it happens:confused:
A low gas charge will also cause the book symbol and warm air after an initial cooling due to the low level of gas in the system being unable to cope with the thermal load from prolonged use...

[davus]

hi guys,

thanks very much for the reply.

I think ill check out the clutch mech in the compressor, but id have to suspect low gas.

As a side note i had a look at the EAS Unlocker V3 software/hardware solution, but it appears (through a few emails with the developer) that it doesnt do airbag, ABS, HEVAC etc........so i think i need a different solution.

Realistically, the money to buy one is worth less than fluffing around for hours on end trying to pinpoint these issues!.

But still having no luck finding one that can do the job for me.

Dave