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6 Posts
Discussion Starter #1
I apologise if I am going over old ground, can't find anything in the history. My AC does not function and shows the open book, is there any way to find out the source of the problem besides a dealer visit? Is there a way to reset the system?

Bill leacock

701 Posts
There is no way to plug into it to find the fault without special rover equipment. However, you could check to see if there is a 12v signal coming from the compressor. If there is, you have a compressor clutch problem and it will need to be shimmed. If it is not getting a signal, you need to find out why. Go to the fuse box and check a/c and fan fuses, also check some of the ones that don't have picture lables, I've found that those can keep the clutch from engaging. If everything appears fine there, push the a/c off button until the light disappears. The rpms of the engine should change. If they don't, it could be your climate ecu. It could also be a pressure switch. Start with the basics first, and then go from there. See if you can get the clutch to engage by applying 12volts to it. Good luck.

btw, my book light is goes on and off at random. Nothing is actually wrong with the system. I suspect a blend motor might be on the way out, but we'll see.

Legacy Vendor
341 Posts
I believe that Dennis of Rover Renovations is now in NY. Worth dropping him a line to see if he has a multi-vehicle HVAC-licensed FaultMate module that can read your fault codes... I understand he is partial to Martinis `8)

If you were in Canberra, Australia I'd do it for you for the princely sum of a decent bottle of red or a half-case of Coronas :D

LRscott has a good point... it is often the blend motors that give grief. Sometime you just need to force them to recalibrate and all is good.

Cheers, Paul.

896 Posts
No easy way to read the computer. I am having issues with my book symbol, but my AC stills blow cold. Start with these diagnostics to troubleshoot the book! symbol...
Range Rover HEVAC

This is really a straight forward functional test. You should have a small torch(flashlight), possibly reading glasses if you use them, and maybe a straightened paper clip.

When finished you will have tested :-
the Air Con compressor (and chilled air output),
the in-car temperature sensor,
the solar gain sensor,
both blower motors,
the distribution flaps/motor,
the recirculation flaps,
and the blend flaps that mix hot and cold air.

For these first two checks, the car and engine can be hot or cold.
Identify the in-car temperature sensor, this is behind the grill positioned just below the clock. There is only one sensor.
Peer through the grill with the torch, and glasses if required. Look sideways, there is a small fan, like a drum with blades on the outside, not like a propeller / radiator fan. Without starting the engine, switch the ignition on, you should just hear the fan running, and be able to see the blur of the blades moving. As a last resort, gently, GENTLY, probe sideways through the grill with the end of the paper clip. Withdraw when it vibrates!
The fan is there to improve the effectiveness of the sensor, by drawing air across it. Fan failure won't stop the system working, but the control of the internal temperature will be poor. The heat will stay on too long, or off too long, leading to wide variations from the set temperature.

Recirculation flaps.
You need quiet for this. Turn the ignition on, but without the engine running. Wait for the brake pressurisation motor to stop running (30 to 45 seconds). Turn the Fan Speed (blower motors) down to minimum.
Operate the recirculation control and listen for the flaps moving. The noise will only last for 5 seconds or so. There is one flap on each blower motor. The blower motors are underneath the dashboard, above your kness rather than ankles, but against the outside of the car. The flap motors are very quiet. The flaps will move again when the recirculation control is restored. Repeat as required.
If you cannot hear them, you will have to test them while the car is moving. When the car is warm, switch the recirculation control on. The car will become noticeably stuffy within about 5 minutes. Switch recirculation off, and the atmosphere will clear.

Now have the engine at normal operating temperature, ticking over, with the A/C switched on.
I assume the book symbol is still showing. The system will self check every time the vehicle is restarted.
If the fault disappears, so will the symbol.
Compressor / chilled air faults will be self evident throughout these tests, no Cold Air.
If this is apparent, open the bonnet, and with the engine running, have someone switch the A/C on and off. There will be an audible click from the Compressor as the clutch engages. Placement of the compressor varies from engine to engine.
Remember, in the absence of chilled air, either through a faulty system, or because the A/C is switched off, the system will substitute external air, at the ambient temperature. In some parts of the world (rarely in the UK) this can be hot. Thus sometimes "cold" air is hot.

Distribution Flaps.
Set both Driver and Passenger temperatures to 16.
Turn the Fan up to get a decent airflow, that is half or threequarter speed.
Using the manual buttons, direct the air towards the footwells. Check with your hand that the airflow is of similar strength and temperature.
Note any side to side differences.
The air issues from triangular holes on the sides of the transmission tunnel above your ankles.
Check there is no air flow from the Facia or Screen outlets.
Use the buttons again and divert the air towards the facia vents, remenber to have them open, check again for flow and temperature.
It takes a few seconds for the Distribution flaps to move to the new position.
Check there is no flow from the non selected outlets (Footwell and Screen).
Use the buttons again and divert the air to the screen, check again for flow and temperature, especially any side to side differences.
Assuming the airflow moved correctly from footwell to facia to screen, and DID NOT appear from any outlets that were not selected at the time, you have proved the Distribution flap / Motor works.

Blower Fans.
With the air issuing from whichever vents you find most convenient to monitor, turn the Fan speed up and down.
Check the air flow varies on both sides of the car. There are two Blower motors, one Left, one Right. They should both change together as you adjust the speed.
Assuming they do, you have just proved the blower fans work. Leave them on half or threequarter speed.

Blend Flaps.
With the air issuing from whichever vents you find most convenient to test, raise the Drivers side temperature to 22, wait a few seconds, can you feel a temperature difference when comparing Driver side air ouput to Passenger side air ouput?
Raise the Drivers side to 28, there should be an obvious difference in temperature.
If the Drivers side airflow temperature has not changed, the Driver side blend flap is faulty.

Reset the Driver side temperature to 16, then repeat the test, varying the Passenger side temperature.
If the Passenger side airflow temperature does not change, the Passenger side blend flap is faulty.

Solar Gain.
The solar gain sensor is a black button on the centre top of the dashboard, near the windscreen (near the Alarm LED).
With engine ticking over, and A/C on, switch it to AUTO mode. Adjust both temperatures to a medium/ low setting, (16 to 22) and let the system stabilise, with the blowers running but not too fast. Shine a bright torch on the Solar Gain sensor, it may take 30 seconds or so, but you will hear the system adjust to compensate for the additional heat, probably by increasing the fan speed. Remove the torch and the system will adjust back, give it a minute or so.
If the system compensated for the additional heat, the solar gain sensor works.

In car temperature sensor.
This is situated behind the grill below the clock.
With the system set as for Solar gain, heat up the Cigar Lighter, and hold the hot end in front of the grill, but not close enough to melt the plastic!
1 to 2 cm should be fine.
If the system compensates for the additional heat, the in-car sensor works.

Additional information.
When on Auto, if a number is showing in the temperature setting, the system will control the position of the blend flaps, dependant on internal temperature, external air temperature, etc. If you adjust the setting to LO, the blend flaps are forced to the end of their range, to deliver ONLY cold air, whatever the actual temperature is, inside or outside.
Remember Cold air will be hot if you are in a hot climate and the A/C is switched off.
If you adjust the setting to HI, the blend flaps are forced to the end of their range, to deliver ONLY heated air, whatever the actual temperature is, inside or outside.

That's it, you should now know what functionality is absent, and can start checking repair costs, or read the (future) article on known faults, repairs and workarounds.

6 Posts
Discussion Starter #6
Thanks for the tips, I found that the interior sensor was covered in hair and cleaned it, but the sensor fan still works. I found that the flaps work, then I checked the refrigerant and found it to be low. After a charge, the compressor kicks in now. I replaced both the relays for the fans, but the blowers still do not work and I still have the test book symbol. If I adjust the blower speed, the symbols show on the screen, but do not get very big, but the fans do not work. Is there a method to force them on? I tried jumpering out the connections at the relays, but nothing happened.


896 Posts
Also check the fusebox where the RL7 relay plugs in. The fusebox tends to crack from overheating and I am looking at replacing my fusebox soon myself. Sounds like the blower motors are bad. Check with Scotty in socal as he may have some good used parts. No telling what made both go bad, but I would try and put power and see if they run. I have heard of the brushes going bad but they could just be burned out. Good luck.

1995-2002 Range Rover P38A
1,851 Posts

If you turn the knob on your ecu the indication bar at the top should move from the left all the way to the right, and blower speed should increase accordingly. If this doesn't work try it on automatic mode and have some patience because it takes some time for the system to react.

If in auto the fans work and increase in speed after some time because setting temperatures can not be obtained, most likely the small copper fingers at the inside of the control knob have fallen off and the ecu does not register any input from the knob.

If you search my previous posts I have pointed it out before, and there are some photo's on the main pages that I referred to so that you will understand what I mean.

If all this doesn't help you, you can supply 12 VDC direct to the fans. At the top connector there are two spades and if you apply power there the fan should start moving at full speed. When doing this test make sure you disconnect all connectors to the fan or you might blow up the speed control electronics.

The control system is a bit complicated and works with a signal from the ecu and the elctronics supply the differential power between the 12 VDC and the ecu signal voltage to the motors. The maximum speed is obtained when the ecu signal is earthed to 0 V. This means that there should be 12 VDC present always at the red wires connected to the fans.


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