RangeRovers.net Forum banner

1 - 11 of 11 Posts

·
Registered
1995-2002 Range Rover P38A
Joined
·
217 Posts
Discussion Starter #1
Greetings from Melbourne Australia.

Well I wouldn't say it's been all fun but there is a sense of satisfaction in keeping what is a great car going.

Over the last few months I've been putting my 2001 Vogue back together; I blew the heater core because I ignored the sudden temperature spike, thinking it was a random measurement issue; instead the water level was low, causing an air lock which blew the core. Do not ignore the gauge going to maximum and the red light on suddenly! I know, obvious in hindsight. Slow water leak seems to be the water pump. I'll deal with it later after I get the cooling system tested.

So I took the dash out (for the second time), replaced the heater core and O-rings, fitted bigger decent hex screws fitted where the pipes meet the heater, removed both blower housings to replace the fresh/recirc motors and two power transistors in one blower motor which was blowing full on, replaced two or three of the blend motors with newer ones after opening them all up and putting them back together, removed the carpet and dried everything out, removed and lubricated every plug and socket I could see with contact cleaner, replaced the battery and tidied everything up.

Everything appears to be working perfectly! Except the testbook symbol comes on after a few minutes even though there appear to be no faults.
Both temperature controls seem to be working perfeclty; I can feel the temp change from cold to hot on both sides and hear the motors whirring when I adjust the temp.
Both fresh/recirc motors are working perfectly; with the pollen filters out I can see the flaps moving from closed to open.
The distribution motor appears to be working perfectly; with the dash still apart I can see the big white gears moving through their full cycle.

What may be wrong?

Should I get the car diagnosed by a bloke I know with the right rig on his laptop and get the fault?

Any direction would be much appreciated.

Tom
 

·
Registered
1995-2002 Range Rover P38A
Joined
·
494 Posts
hi tom I had a similar problem not being able to get the book symbol to disappear , after repairing all things hevac, the book cymbal stayed . I then fixed the issue with the air con and replaced the relays on the blowers again ands it has gone, (don't just think there good) . you can obtain the software to read the hevac system with a obd2 cable and a laptop. maybe someone else can chip in their as I have a reader for this
 

·
Super Moderator
Joined
·
2,231 Posts
While the fans and blend motors are the obvious things to bring on the book symbol, there's other less obvious ones. A dash aspirator clogged with dust, a failed heater core temperature sensor or a failed intake air sensor won't be immediately obvious but will log a fault. You need to connect a dedicated reader or software to read the fault codes and identify what isn't working.
 

·
Registered
1995-2002 Range Rover P38A
Joined
·
217 Posts
Discussion Starter #4
Thanks Richard.
Where is the intake air sensor located?
Appreciate the help.
Tom
 

·
Super Moderator
Joined
·
2,231 Posts
That's the aspirator that measures the interior temperature, the intake sensor is behind the grille, in front of the radiator/AC condenser on a 2001, on earlier cars it's in the air intake trunking after the pollen filters.
 

·
Registered
1995-2002 Range Rover P38A
Joined
·
77 Posts
Could very well be your fusebox. Check for under the fan relays for cracks/heat damage. That threw the book symbol at me till I replaced the fusebox. And as an added bonus I finally got the high speed fan I didn't even know it had.

Best of luck.

David
 

·
Registered
1995-2002 Range Rover P38A
Joined
·
217 Posts
Discussion Starter #8
Thanks to all who replied to this thread; I've only just read the replies now; it's only polite to acknowledge help given. My issue has moved on a bit anyway but hasn't given me too much grief lately; in the middle of a Melbourne winter, my two heat controls live pretty much on HI lately.

Without ready access to a diagnostic reader, I'm doing this by process of elimination. My right blend motor seems to be the issue. Both blower fans work at maximum speed, so I don't suspect the fusebox which seems to be in perfect shape; it was replaced a few years ago BUT I have not checked under the PC board there.

The issue is my right hand (driver's side) blender or controller is faulty. It works fine on HI; the temp on both sides feels the same when both are set to HI but the temp betwen LO and HI is erratic or doesn't change with the correct gradations that the left hand side does; I can hear the blend motor on that side moving correctly, whirring and adjusting the temp properly.

I've removed the RH blender and checked it; all the gears work perfectly; no stripped teeth and it's as torquey as it should be. Last time I was in there the internal flap in the heater box was moving freely and easily. I checked the internal pot in the blender too which moves correctly from 0 Ohms to 10 kOhms.

The coolant sensor on the heater pipe under the dash is just one feed for the entire HEVAC I think so I don't think that's the culprit.

Now I suspect the HEVAC controller. How about I get in there and swap the cables for the left and right blend motors and see if my problem changes sides? Before I do that, I thought I'd check in here.

Always grateful for any help.

Tom
 

·
Super Moderator
Joined
·
2,231 Posts
Wouldn't it be easier to get the faults read and save yourself lots of poke and hope? You shouldn't ever need to put the temperature on HI, just set whatever temperature you want and let the HEVAC deal with it, as soon as the heater core is getting warm it will speed up the fans to get to your desired temperature as quickly as possible then maintain it. Does your AC work? Even when set to HI the AC will kick in to dehumidify the air and that will cause the book to appear after it has been running for a few minutes as it tries to engage the AC clutch and fails.
 

·
Registered
1995-2002 Range Rover P38A
Joined
·
217 Posts
Discussion Starter #10
Thanks, Richard.

Yes, the AC works; it's the Australian essential...

It turns out that my RH blend motor was faulty after all. Running the RH side on HI was the only way to get any heat of that side; anything between LO and HI only seemed to produce temp around 20 degrees C. I needed to change it anyway before I got the car scanned which I will do soon.

Having some spares on hand, I changed it. I'd previously cut and removed the duct going to the rear seats so it's quick and easy to change the blend motor. Funny that I'd carefully tested the potentiometer within the motor without it showing any dead spots; it's logical to think that the dead spots or faults within the pot itself would be around the 21 - 22 degree C mark since that's where it spends most of its time, but I did not measure any anomalies when I swept that pot initially.

Now I have perfect, even heat from both sides of the car; something I've never had in two years!

I can easily detect one degree changes in temp just by feeling the air flow.

So I think it all works as it should. Amazing stuff.

BUT I still have the book symbol on after 10 or 15 minutes' driving time.

This is my mission; clear the book symbol!

So now I'll get the rig scanned and see what's causing the issue. I think it can be only the coolant temp sensor on the heater pipe or the control unit itself.

Tom
 

·
LEGACY VENDOR
1995-2002 Range Rover P38A
Joined
·
4,219 Posts
I haven't read through all of this as I'm at work, but just on your last post...

My guess would be either the blend motors need calibration, as one of them goes outside of it's expected range on occasion and that causes it to throw a fault, or as you mention, one of the sensors isn't showing the correct value - or is OK until it's warmed up and then goes open circuit or intermittent.

The actual HEVAC controllers, despite some things on them being a complete pain, seem to be pretty robust, and hardly ever fail. The normal failure for them (aside from the pixels on the screen going) is the output drivers for the blend motors - but if one of those fails, then you get a permanent error, and the motor won't drive at all. The driver ICs are replaceable though, so even then the units can generally be repaired.
 
1 - 11 of 11 Posts
Top