While I have some time over the festive season I'm trying to work out why my heater intermittently blows hot & cold. AJ 4.4V8 06 petrol L322. I've read all the previous posts, but nothing to pin point my issue.

One time it will work fine on manual or auto, reaching the desired temperature, next it will blow hot & then turn to blowing cold air. Having to switch the engine off & hope that it will blow hot again.

1. New radiator & expansion tank fitted & bled no air locks, constant Normal temperature (No low reading & no overheating).
2. New auxiliary pump & bulk head valves fitted ( No FBH fitted or secondary value fitted).
3. Center vent cleaned & cabin sensor fan operational.
4. Blower works on all speeds, Max operational on Max heating & cooling cycles.
5. Heater pipes to matrix getting hot & AC works fine.
6. All flaps working manually, including blend vent & set to 3 red dots.
7. Rear cabin heating does Not get hot separately.

I can only assume that for some reason, the system believes that it has reached the required temperature & therefore will not increase the temperature. I will look at both the heater temperature sensors ( two fitted as it's the high line system) to see if they are clogged up giving a false reading (unsure how to test them).
Has anyone else replaced these & did it make any difference?.

I was also thinking about the cooling system thermostat, Is this sticking?, but why does the system heat the cabin again once I've switched off & restarted the engine.

Any advise from members who have had similar issues & fixed it would be much appreciated.

Has anyone changed the heater temperature sensor/s?. Mine has the High line system therefore should have two, Finding one would be nice.
Had the center switches out & both the the foot well covers, but nothing (found the temperature A/C sensor & all the flap actuators etc). My lower steering wheel trim is different to that shown in the workshop manual (all one piece) & had a good look under both sides, but nothing

On a long drive last night mine might be doing something similar, cabin unduly cold then fine after a restart. I noticed that the rear air vent was only ever blowing cold in any setting. Mine is a 2006 4.2 supercharged with the pre-facelift interior.

Have you tried blowing any dust out of the little vent on the heater control panel, it's next to the directional buttons I think. I believe this does something to monitor cabin temperatures.

That is going to be my first port of call. Otherwise i can't help with a solution, but let us know how you get on.

Sorry a bit OT, but both my L322s had weird heating - I thought it was a 'design feature'/'they all do that' issue.

Thanks for the replies. Already cleaned the air vent & fan working fine, as this was my first point of call. Knips, I know the L322's heating can be a little temperamental at times, but I shouldn't have these issues. I'll update once I've fitted the new sensor.

Update:- Replaced both the temperature sensors & feels better. Cleaned the thermistor & checked that it was working by doing a resistance check.
Still appear to have a flap selection issue to some degree. If i have the flaps set manually to screen & select foot well, I can see the motor link rod physically change, however this is not instant & not always happening.

If I turn the fan off & then back on again, I can then see the link rod move.

I assume that the flap direction change will not be that quick, but why will it not always change on request?.

Although the heating appears to be satisfactory, I would like to sort out the directional change issue. Loathed the dismantle the linkage / motors etc, as they work & seems to be signal issue.
Can the BCM be reset or best left alone.

Hi, did you ever sort this issue out as i am having a similiar one. Went in to an indy to have a leaking thermostat fixed now its been returned and the weather getting cold i have noticed the heater is blowing cold air no matter how high i turn the temp controls up passenger and driver side.
It was working prior to the thermostat leak fix but may not be related. Also own a 1976 Land Rover 101 3.5 V8.
Previously owned 1991 Range Rover Vogue 3.9 V8.

Nope:- Heater works perfectly fine until you get up to any speed. It then blows cold.

Basically the control valves are shutting off the coolant flow to the heater matrix, slow down & you have heat again. It's got to be an electrical issues & may try giving the control valves a permanent feed to see if that cures it.

All new parts replaced & No faults show on IID tool, Land Rover have no idea

I've only ever seen one other similar issue many years ago by AKKIS on the forum & he never found the issue

Around town it's fine, however coming back from the airport after being in Lanzarote in the snow the other night didn't help & really did me off. Only compensated by the heated seats / front screen & steering wheel!.

landy95, Yours sounds like an air lock.

landy95 wrote:

Hi, did you ever sort this issue out as i am having a similiar one. Went in to an indy to have a leaking thermostat fixed now its been returned and the weather getting cold i have noticed the heater is blowing cold air no matter how high i turn the temp controls up passenger and driver side.
It was working prior to the thermostat leak fix but may not be related.

Thank you both, i was thinking its more than likely an air lock but have not had time to investigate yet. Im going to have a look this afternoon hopefully, i will keep you posted.
Cheers
Neil Also own a 1976 Land Rover 101 3.5 V8.
Previously owned 1991 Range Rover Vogue 3.9 V8.

I had all sorts of strange heating problems years ago turned out to be the air filter housing on the bulk head as at speed it was letting air flow direct in to cabin worth a look

Thanks Sandyt, Unfortunately already looked into this. Also tapped up all the inlets to stop any air coming in at all, but still the same.
Will have another look at the weekend

I recently had the same issue caused by an airlock due to a tiny coolant leak from a faulty hose clamp on my lpg vaporiser. It has driven me mad but I have finally managed to shift the air lock.

Old fashioned method.....I shoved a garden hose in 1 end of the vaporiser hose blocked off the other left the expansion cap.off and turned the hose on gently mind........all sorted and iv since added anti freeze so I'm good to go.

Had to do the same thing on my p38 a few times .

Dave, I tend to agree. Although I have bled & bled, I think its it got to be that.

I was thinking electrics, but having replaced everything & checking the feeds, it's got to be something simple.
The control valves are the open valve type & close when energized. Trying to see how the matrix get fed when the valves are closed, as the valves feed the two out of the three bulkhead connections (the third is the return). Trying to find a decent cooling flow diagram, showing the hose layout. Got a few but nothing really good.

I'll have a look tomorrow & see how they are routed. Also shove the hose through everything. Let you know the outcome. Paul.