Hey Gang,
I recently went through a ton of work to get my AC blowing cold. I finally worked out that it was the expansion valve. Once I got the new one in, she was blowing frosty in a matter of no time.

Unfortunately, my book light is on permanently. The truck will only blow cold air now (it used to blow only hot). The techs told me I needed a new heater core temp sensor, could that be the reason the light is on for good now?

Does anyone have any suggestions on how to determine if the heater flap blend motors or the blower fan flap control motors are at fault?

Thanks!

 

The temp sensor gets clogged, it is located under the clock. Take some compressed air and blow it out. However, because the book is illuminated this leads me to believe it is a blend motor failure. http://rangerovers.net/repairdetails/blendmotor.html

 

Congratulations on getting the cold air working! The heater core temp sensor is not the same as the interior temp sensor behind the clock. If either sensor fails it will trigger the book symbol.

Generally though if the heater core temp sensor fails it will blow only warm/hot air...

Here's a useful guide from David Sparkes at landrovernet.com:
This is really a straight forward functional test. You should have a small torch, possibly reading glasses if you use them, and maybe a straightened paper clip. Technical isn't it?
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.

 

Did not know you could do all of that ldivine! I am recording your comment for future diagnostics lol!

 

Thanks ldivine!
I think I have isolated it to the drivers side blend motor. I've heard rumors that one is fairly easy to get to. I'll have to check out the RAVE manual and have a look.

 

Hi

I have just got my 1st Range Rover with a few lol issues.

I saw your post heres a better way toget to your blend motor.

http://www.rangerovers.net/repairdet...lendmotor.html


They show a quick way to do left hand side.

My issue is my fans blow red hot air at the windscreen no where else, I think its right hand side so not easy.

Hope the link helps, weirldy my RR has a lever thats been retrofitedto the left hand side, i think they may have done this at some point save fitting a new servo.

Thanks

Charly

 

As we corresponded on this before, I wish your issue was as relatively simple as mine on the old P38 has continually been. This past weekend we picked it up from having the ABS pump replaced. When we got there, the "notebook" light was on, again. Fortunately, I keep a spare relay in the glove compartment. Popped it in, light went off - cold air blowing full steam again. You can see a small burnt area in the relay panel under the hood, and that same prong on the corresponding relay burns out about twice per year. Yes, there may be a bigger issue - but at $24 apiece at NAPA, this works for now -- and has for 4-5 years.

 

Hey thanks for the reply.

I am not 100% sure whats up with mine yet not had chance to get under the dash, mine just blows hot air at windcreen so hoping its just 1 of the blenders.

How can you test the relay and which one is it lol just point me in right direction, if any one knows how to test them let me know as i have a volt meter etc

Charly

 

Gibsoft,
On late production P-38's you'd check fuse 8 and 17. I'm not sure if early model P38's had different fuse configurations--- you can always check through RAVE.

Easiest way to test the fuses, if you don't detect any visual damage, would be to substitute another compatible non-essential fuse (one you know works) or to buy a new one and exchange it with a suspect fuse to see if that fixes the problem.

mlshelton is referring to a relay that is a common culprit of a problem other then the one you describe (inoperable or slow blower fans) and I believe he may have been directing that comment at another user.

But do check the fuses as they *may* be the problem. Best of luck!

 

Wow. What a load of work.

I replaced the expansion valve and recharged the system. That got the cold air blowing. That worked for about 2 days.

Eventually it was blowing hot air on the driver and cold everywhere else, obviously a blend motor issue.

I took out the dash and followed the instructions from the RAVE manual and got a new blend motor installed. I spliced it into the line in order to save a little time, and it worked perfectly fine. Cold air was blowing everywhere it should and things were good...for about 2 days.

The book light started coming back on intermittently. The techs told me that I needed a new heater core temp sensor a while back, so I replaced that. No more book light, for now. I wouldn't be shocked if it comes back.

Thanks for all the help guys!