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1995-2002 Range Rover P38A
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Discussion Starter #1
LHD 2.5DSE 1999 pre EGR/MAF

Hi, I have an issue with the HEVAC I've been considering to check for a while. It's not that big of a deal but it could become one later on so better to deal with it now.

As per the title. When driving on the street and making 90° turns I notice the air from the vents turn cold for a few seconds. And also the car for some reason rolls off the road, flips a few times and hopefully land back on the tires.... mainly in high speeds.

I don't know wether it also gets cold on the passenger side.

I have read the excellent Blend motor diagnosis page and I am suspecting the left hand temperature blend servo.


One other thing not really related to the blend motors is the book symbol is permanently lit and according to the previous owner it appreared when the compressor clutch and/or bearing seized up and he had to cut of the drive belt.
The system has no refrigerant left I realized when the condensor was removed by myself and scrapped due to corrosion in the bottom of the cells.

Is he correct when he said the book symbol appears because of the clutch seized up? I'm not sure if the connector for the clutch is connected.
Or does the HEVAC light the book symbol because of the lack of refrigerant?
 

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If the car "flips a few times" and then "lands back on the tyres", surely cold HEVAC air is the least of your worries ?? Maybe turn slower ?
 

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Yea, not a blend motor issue. Sounds like low coolant or a failing water pump impeller. Since the P38 heater core is full flow at all times it should have full temp coolant at all times. If your coolant is low there is not enough coolant to maintain the heater core at lower speeds. Same with a failing water pump. Higher RPMs provides more flow. Low RPMs mean minimal flow if your impeller is corroded or loose. At a far stretch your heater core could be partially plugged up but that usually presents itself with weak heat at all times and would not vary so drastically with RPMs

Check coolant level and check flow at the coolant tank.
 

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1995-2002 Range Rover P38A
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Diesels are known for failing coolant pump impellers. If you replace it, be sure to get a metal impeller version, not plastic.
Keep the coolant level high, backflush the heater matrix if you like (may as well as you're going to be draining the coolant). Check the thermostat is working correctly- again the diesels have a tendency to run cold.
Oh yes- as Chris and Pete have mentioned, either reduce your velocity when testing on those sharp 90 degree turns, or leave imbibing that Norwegian homebrew Akevitt until road testing is finished and you're tucked up in front of the computer :)
 

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Discussion Starter #6
Yea, not a blend motor issue. Sounds like low coolant or a failing water pump impeller. Since the P38 heater core is full flow at all times it should have full temp coolant at all times. If your coolant is low there is not enough coolant to maintain the heater core at lower speeds. Same with a failing water pump. Higher RPMs provides more flow. Low RPMs mean minimal flow if your impeller is corroded or loose. At a far stretch your heater core could be partially plugged up but that usually presents itself with weak heat at all times and would not vary so drastically with RPMs

Check coolant level and check flow at the coolant tank.
Coolant level is definitely ok and I'm positive there is no airlocks. Will check coolant flow at the expansion tank. How much is enough at idle?
Just a couple of hours ago I had the chance to check wether it also blows cold on the passenger side cause my wife was also in the car and It does.
While on my side the air turns warm again after a 4-5 seconds it kept blowing cold on the passenger side window air outlet.

My temp gauge is rock solid at 11 o clock when the engine is at working temperature. So that tells me the pump should be working ok-ish. But I could have a look at it.
Thermostat is new, the old one opened too early.


Thank you all for your replies.
Will consider slowing down while testing and keep the high speed 90° cornering to....other times.
 

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Discussion Starter #7
Hi all.

Did some testing with an infrared thermometer. The following temp figures will be in Celsius.
Engine at normal running temperature.
Gauge in dash shows temp at 11 o clock as usual.

Temp at hose from back of engine block to heater core: 99°C
Temp at hose from heater core back to engine: 97°C
Temp at hose from engine block to radiator: 95°C
Temp at return hose from radiator to thermostat housing: 60°C

This tells me I have sufficient flow at idle. Also that almost no heat is transferred from the heater core.
Passenger side is cold, no matter what temperature I choose in the panel.
Driver side regulates the temperature at least but not enough I'd say. Luke warm-ish.

Clearly the passenger side blend servo is stuck, but the driver's side? It's so strange that gust of cold air is blowing when turning the vehicle. Especially to the left.
Will order a set of servo motors and start from there.

Is Britpart ok or is it advised to buy genuine Valeo?

Thanks!
 

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I would look at heater core some cores loose the flow director in the core itself . basically it works like a bypass system , straight in straight out . the only way you can see if its the core is to remove the plastic tank which will basically destroy the core. would not advise you to buy cheap blend motors as they are not the best , would not advise you to buy new motors unless you need them, expensive . if you end up removing the heater box make shore the diverter flaps move easily . test blend motors on the bench with a 9 volt battery , you can repair them, all well documented in other threads. I think you are doing what I did, avoiding the dash removal , It only took 2 days , how long has this taken?
 

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Discussion Starter #9
I would look at heater core some cores loose the flow director in the core itself . basically it works like a bypass system , straight in straight out . the only way you can see if its the core is to remove the plastic tank which will basically destroy the core.

Non Range rover related anecdote:

A few days ago I did some maintenance on a machine at work which had no heat in the cabin.
Basically the heater core was so full of rust it was almost completely clogged. At idle no coolant was pumped through. At high rpm the heater core was heated to 60°C but could not maintain the heat when cooled by the fan.
I thoroughly cleaned it by running water from a tap through it cycling cold and hot water and banging it against the sink. Could not believe how much it was. Took me 40minutes to clean it.

Did the same with the whole coolant system. Rust everywhere. That engine had not had a change in fluid at the correct interval I can tell you that.

Back to Range Rover land:

I guess the only way to find out if the flow diverter is loose is to remove the heater box and run hot water in it and feel if it gets hot uniformly.
I did replace the O-rings a while back so I have been in that area before. Did not like it one bit. Considering to swap it for an audi heater core.

would not advise you to buy cheap blend motors as they are not the best , would not advise you to buy new motors unless you need them, expensive . if you end up removing the heater box make shore the diverter flaps move easily . test blend motors on the bench with a 9 volt battery , you can repair them, all well documented in other threads.
Would it be possible to test them in the vehicle applying voltage to the multiplug and listen and maybe by touch feel if it's moving.
Why 9V by the way?

I think you are doing what I did, avoiding the dash removal , It only took 2 days , how long has this taken?
Are you saying I should just go ahead and remove the dash and figure out what's wrong with everything that way?
 

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the blend motors are only powered with 7 volts I think, 12 volts will over power and damage units .If you want to see the blend motors remove the instrument panel and look in their you will see them operate, this is reference from a RHD (2 of 3 that is, the top one is the distribution motor, lower is temp controller) you can remove the distribution motor and try to move the flaps , they should be easy to move with your fingers ,if you can't move these then you need to remove your heater box (dash out)and free them up by sanding the inside of the heater box. the plastic box shrinks and squeezes the flaps in the box so they are to tight for the motors to drive . yes you can operate the blend motors bye removing the hevac unit and power up the plug with the 9 volt battery . all well documented in other treads. I tried all the little tricks ,3days off wasted time later , out with the dash 2 days later all fixed. cost $4 for orings . hope this is of some help.
 

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Discussion Starter #11
Today I started looking at a few items in my cars cooling system.

The viscous clutch failed on me a while back. It overcooled the engine sounding like a jet plane taking off stealing a bunch of power. Dang vicious viscous clutch. Took the one from my spare engine. Not the same fan. Different angle of the vanes, but it works. Sort of. It does lock up awfully often sounding more like a vacuum hover than a jet plane.
I live in a not so hot part of the world so I ordered a couple of adjustable thermostats to control the condenser fans instead and just get rid of the belt driven fan and shrouding.

The radiator was replaced a few years ago and I've been wanting to inspect it for a while because of a suspicion I had that it had a failed or missing baffle. Had a hard time feeling any heat in the lower parts of the radiator. Turns out it was good. Could be it merely was cooled by the fan running all the time.

Waterpump impeller. Removed the water pump. It has an orange plastic impeller. It's not loose, but I can slightly wiggle it a little between the impeller and metal bushing.
I compared it to the water pump from my spare engine which also was plastic but green. Had no play at all. So considered to use that one for the time being. But, it's missing something. It doesn't have the "spill port" (don't know what it's called, to inform of a failed seal spilling the coolant out, instead of containing the leak internally, and one day result in a catastrophic bearing failure with other costly repairs.

Took a look at a new water pump with metal impeller and it does have that protrusion on the image.
http://www.island-4x4.co.uk/water-pump-stc2192g-stc3342g-metal-impeller-p-1389.html

Will continue using the orange one. Probably been changed at least once. The o-ring was bad so I'll use that at least from the spare.


After I'm done with these things I will continue to the interior and start checking the blend servo's.
 

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Discussion Starter #12
Update:

I've been collecting parts lately to hopefully fix all my under the dash related problems.
Today I wanted to see if I could get rid of the textbook & exclamation mark from the HEVAC temporarily.

1. Compressor broken. Bypassed the pressure switch to energize the compressor coil which I removed from the compressor. Works ok. Coil is magnetized when vehicle is started.
2. Put in a brand new blower motor on the right hand side. OK
3. Connected a brand new genuine Valeo (supposedly) blend motor assembly to see how they move. NOT working ok.

Textbook lights up as ususal. Only one of the servos move and that's the distribution one. I test all settings and when I come to the far right one, Arrow pointing up from footwell, it decides to make a permanent pit stop there. Refuses to move again.
I shut off the vehicle, disconnect servos connector and try again. Servo moves around on all settings but the one to the right. Tried the others forwards and backwards numerous times and lastly the right one and it stops again.

Heater servos does not move at all!


I disconnect the new set and connects the one in the car and test everything. Works like usual with the faulty heat servo on the right side.


It must be a duff unit right?
 

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Discussion Starter #13
Tried the 9 volt battery temporary fix.

Heard the servo moving and disconnected the 9 volt battery when I heard it ran heavier.
Started the car, and wow, the Textbook was gone for 10 seconds. Now we'll have hot air on both sides at least for the time being.
 

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sounds like the heater box needs attention , sorry to say but I think it has to come out. if you have removed the front console you can remove the front of the heater box after cutting the cross member to check how tight the flaps are . in all honesty you are basically half way there so just keep going, follow the Pauls P38 dash removal procedure with the addition of removing the outer leaver from steering column, its just easier.
 

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Discussion Starter #15
Yeah, that's what I'm planning to do.
Hence the collecting of parts. :)
Gonna try to avoid short cuts.

1. Checking flaps in heaterbox, grind when needed.
2. Replacing the blend servos
3. Replacing the heater core to an audi one.
4. Fixing annoying diffuse rattle @ 1200RPM
5. Installing an AOI airbag switch for the passenger airbag. Possibly mounting a yellow led in dash.
6. Running a thick wire between the blower motors for nr 7.
7. Installing two DPDT relays to the blower motors to run them in series to prepare for a future Webasto parking heater install.
8. Duct-taping every joint of the air ducting.

That's about it.
 

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there is a couple off parts you may need 4 millimetre thread stock , 2 packets of furniture fixtures (like flat washer with internal thread) 1 that screw to the thread stock and 1 that slides over thread stock and 6 nuts that you can use as lock nuts. the idea is to make spreaders for the top of the heater box only . the top dampers are difficult to remove , easier to just fit the spreaders. I do have photos some ware will look for you
 

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Discussion Starter #17
Pictures are always welcome.

The furniture fixtures you speak of. If I can't find any, a piece of flat iron with a drilled and tapped 4mm hole, that would do the same trick no?


About calibration of blend servos.
I wrote a semi-hangry message to the retailer I bought my new Valeo set from.
I explained what I did and what the servos did not. He was as puzzled as the techs at Valeo who never ever heard of a unit that was broken from the get go (funny how all manufacturers no matter what they produce state that).
Anyway, yesterday while researching the subject I realized they need to be calibrated.
I don't have a nanocom or something like that. I don't know anyone who does. There is a Land Rover dealer not far away.
But some threads seem to tell that you can get the hevac to calibrate when cutting power, but not the exact procedure.

I was thinking if this might work instead of calibrating now that I don't have a fault icon:

1. Disconnecting servo connector from hevac.
2. Measure all three potentiometers. Write down the current resistance.
3. Move the servo motors on the new set with a 9V battery while monitoring the potentiometers resistance and stopping when reaching the correct resistance in this case.
4. Connect the new set of servos.
5. Start up and hope for the best.
 

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Discussion Starter #18
Ok, I finally had the time to check this again.
My idea in my last post worked ok. So that is one way to "calibrate" a new set, at least if you can get the old set to work termporarily.

When I attached the new servo set they all can be regulated and no fault code on the panel. Sorry to say though both temperature servos generate a fault code at the HI temp setting. Left 0,8kOhm, right 8,13kOhm.
The distributor servo also generate a fault code AND gets stuck at 0,8kOhm. Arrow up from leg room.

Disappointed!

I'll just have to see what the retailer says about that.


About the old set that's still in the car. Now I had the guts to actually test all settings while listening to the servos work. Changed the temp up to hi and down to lo and it all seems to work. No fault code at all. Ambient temperature is room temperature and the heater box also at that temp.
Maybe my real problem is the right side servo flap is a bit seized a specific temp and all I need is to fix that.
 

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Discussion Starter #19
I'm glad I decided to give this another round of fault finding before sending it back to UK.
I bought an analog multimeter to properly measure the potentiometers of the new set to see if they malfunction.
Turns out they go up and down very smoothly.

So what's the problem then?
I connected the set in the car and started fiddling with them again. Faultcodes at the same settings again. Hi temp both sides and Arrow up from leg room.
Then I measured the old set in the car at hi temp settings and arrow up to get a reference point.

Left HI = 2kOhm
Right HI = 8kOhm
Arrow Up = 2kOhm

Oh, so that's how it's supposed to be? Normal operating range is between 2 and 8kOhm. Not from 0,8kOhm to 8kOhm.

All servos require a mechanical calibrated stop for the hevac to work. If there is none they just run right past and generates a fault.
Here I'm guessing but it must be that the temperature servos are calibrated against the flap levers mechanical stop in it's High setting.
The distribution servo is calibrated against it's flap levers mechanical stop at the far right setting. Arrow Up.


Now I have everything I need to tear down my dash and start. I merely lack the time...
 

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Now I have everything I need to tear down my dash and start. I merely lack the time...
Just follow the "PaulP38" process. This removes enough to allows access to remove the heater box, without removing the entire frame. It's actually a lot easier than most people think (Takes me less than 2 hours now I had practice !! ).

Do NOT use the procedure in RAVE which suggests unbolting the entire frame from the bulkhead.
 
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