Strange HEVAC issue with MY 09/1995 P38 Range Rover

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

Quote:

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Originally Posted by davus

Thanks Gary.

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

Dave

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Dave

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

Gary

Quote:

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Originally Posted by mtb_gary

Dave

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

Gary

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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.

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

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:
[ame]http://youtu.be/sLgCHxEaxRI[/ame]


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:
[ame]http://youtu.be/tXqrpzNPooM[/ame]

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


Dave

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

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

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....

Quote:

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Originally Posted by Shirley

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

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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

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

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...