HEVAC problem - p38

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kooky_guy

kooky_guy

Well-Known Member
Posts
2,410
Location
Sandhurst, Berkshire
Hi dudes,

Got the cheque book symbol up - it's been coming on quite intermittently recently but now has started coming on straight away all the time.

The heater seems to be stuck with hot blowing onto the screen regardless of what the distribution settings are. The temp controls don't seem to do much either - heat is either on (and VERY hot) or cold.

Rangerovers.net suggest that it might be the coolant temperature sensor which apparently can cause it to go into this mode, but the temporary fix they suggest has no effect. Any ideas how I could check the temp sensor? I think I know where it is and how to get to it, but not sure what I can do to test/fix it (hammer springs to mind).

I know I should get the fault read but was hoping I could look at it tomorrow as my feet are getting cold!!

Suggestions anyone? I would have suspected the blends if it wasn't for the rangerovers.net article.

Guy
 
eightinavee said:
Look at the bit for fixing the stuck distribution flap with a self tapping screw on the RR net site.
Click to expand...

You think that might be what it is?

I think I've looked at that section before, but couldn't quite get my head round what they were doing. I can't find the article now.

Is that as big a stripdown job as replacing the blends? I've only got a couple of hours free tomorrow. If it's going to be a biggie, I'll just have to book it in somewhere - I need it sorted as away next weekend (supposedly in the Rangey).
 
Needs to go on Testbook to be sure,but thats what it sounds like,its not a bad job,done loads of them - it was my idea to use the self tapper as a result of owners not wanting to pay for a new heater box !
 
eightinavee said:
Needs to go on Testbook to be sure,but thats what it sounds like,its not a bad job,done loads of them - it was my idea to use the self tapper as a result of owners not wanting to pay for a new heater box !
Click to expand...

I'm a bit confused. So you think the distribution flap has jammed rather than the blend stripping teeth? Or is it the flap jamming that causes the blend motor to strip?
 
Hmm. just driven home and it was absolutely fine again - no book symbol and normal heat coming out wherever I directed it. It's been stuck on turbo heat to the screen all week.

I assume the problem will come back but does the fact that its not permanently broken help with a diagnosis?

Guy
 
Yes its does,what I realised several years ago when replacing blend motors I often saw the "Distribution flap stalled during self tune" fault.The flap is supposed to go through its complete cycle of movement every time the hevac boots up.
When those heaters were made by Valeo the distribution flaps weremade too long for the box - they worked OK when new but over the years of repeated heating/cooling the boxes must shrink or distort,which pinches the flaps.Its worse when they are cold,so the flap wont move - the hevac ecu sees it as a fault and inhibits any more temp/distribution changes.If you run the car for a while then switch off and restart it may all work again,this is because the box has swollen enough to let the flaps move.
Your car sounds like an ideal candidate for the self tapper before it does strip the plastic gears,as it trys quite hard before the ecu stops it each time.
 
My distribution used to get stuck , this is what i done, i removed the vents in the centre of the dash and drilled a small hole in the heater box and squirted a small amount of WD 40 in there, the flap has stalled on me twice in 2 years and twice has the WD40 worked for me.
Its worth a try before pulling the dash to peices
 
Ahh. It's starting to make sense now.

What does the self tapper trick actually aim to achieve though. Expand the heater box a bit thus giving the flap a bit more space to move? Presumably the self tapper has to then remain in place?

Blimey, there really are some geniuses on here! Thanks all!

Now why can't I find such a garage near me with such excellent knowledge?!

Guy
 
eightinavee said:
Thats it,the self tapper just forces the two halves apart slightly - enough to free it off,a squirt of wd40 helps too.
As for a garage near you,one of the top independants in the country is very close to you; www.landroversolutions.co.uk, Landrover Specialist Solutions
Click to expand...

Hmm. I might well give it a go then when I get some time. Thanks for the explanations - I prefer tacking a job when I understand exactly what I'm trying to achieve and I was a bit mystified by this. It's been as good as gold all weekend but the wife's borrowed it today so it's bound to break again!

Blimey, they're literally just up the road from me! Thanks for that. I'll check them out.

Guy
 
Cossie David said:
My distribution used to get stuck , this is what i done, i removed the vents in the centre of the dash and drilled a small hole in the heater box and squirted a small amount of WD 40 in there, the flap has stalled on me twice in 2 years and twice has the WD40 worked for me.
Its worth a try before pulling the dash to peices
Click to expand...

So you removed the vents and the heater box is accessible behind them?

Doesn't that make the car stink of WD40?

Mine's doing all kinds of weird things now - temperature gradually going cold unless it's set to HI and this morning I got the stupid book symbol with full heat to the screen again.

Does the HEVAC store fault codes? I'm just wondering if it's worth getting it read as it's not always there.

Guy
 
From memory there are about 22 codes that the Hevac can store.A squirt of WD40 in the self tapper hole is a good move,does not smell for long.(Better than the smell of anti freeze that they normally smell of when the matrix o rings leak:D) Give Baldrick a ring at SVP UK - he can read and sort your codes.
 
eightinavee said:
From memory there are about 22 codes that the Hevac can store.A squirt of WD40 in the self tapper hole is a good move,does not smell for long.(Better than the smell of anti freeze that they normally smell of when the matrix o rings leak:D) Give Baldrick a ring at SVP UK - he can read and sort your codes.
Click to expand...

Hmm. It's definitely being weird. Current fault mode seems to be just that it shows the book symbol after about 15 minutes, but seems to continue working fine.

I'll give him a bell and try to get the codes read and see if they tell me anything since he's only up the road.

Thanks again.

Guy
 
I just completed the operation yesterday, the screw fix works well.

One thing I will say is that you should try swapping the dash control unit first with a known working one if you have access to one. The contol unit is a bit like the EAS driver pack, it can go wrong too.

I went to the trouble of changing the distribution blend motor a few months back after a distribution circuit fault coming up on faultmate. Turned out there was nothing wrong with the original motor - in fact it was better than the one I bought off ebay to replace it!

Changing the head unit solved the problem, and the incorrect external temp fault also - however the unit I bought off ebay had a poor LCD so I ended up having to cannabalise between the two to get a fully functioning unit.
 
Last edited:
SpudH said:
I just completed the operation yesterday, the screw fix works well.

One thing I will say is that you should try swapping the dash control unit first with a known working one if you have access to one. The contol unit is a bit like the EAS driver pack, it can go wrong too.

I went to the trouble of changing the distribution blend motor a few months back after a distribution circuit fault coming up on faultmate. Turned out there was nothing wrong with the original motor - in fact it was better than the one I bought off ebay to replace it!

Changinging the head unit solved the problem, and the incorrect external temp fault also - however the unit I bought off ebay had a poor LCD so I ended up having to cannabalise between the two to get a fully functioning unit.
Click to expand...

Hmm, I was starting to wonder about the HEVAC jobbie itself as my outside temp is wrong too - it underreads by about 4 degrees - and the seemingly random nature of the problems I've been having.

Is it easy to remove or does as much have to come out as for the self tapper fix?

I'm sure someone on here said they had a good working one going spare...?

Guy
 
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