All

With the recent snow we had I noticed that the drivers side vents are not blowing out warm air but rather cold air. The passenger side works fine but no matter what the heat setting is all the drivers side vents blows out cold air. Any ideas on what the issue is?

Thanks

 

clogged heater core or you have air in the system is one possible cause. Do you see bubbles in your coolant expansion tank OR in the coolant return? Fluid should not have bubbles as it returns to the tank.

 

With one side working we know it's not a clogged heater core, but a blend door actuator motor; basically a stepper motor that varies the amount of hot air to mix with ambient air. Each side has its own motor to allow the driver and passenger to choose their personal temperature.

 

Actually with one side blowing cold, it IS a partially clogged heater core at least on this particular vehicle.

See this post from a dealer tech who has replaced a few of these heater matrixes for this reason: https://discoweb.org/forums/showthre...ghlight=heater

 

To add to the heater core info, my local independent rover shop said that they have been doing upwards of five or six heater core replacements on LR3's per month. My understanding is that the driver side of the core is the lowest point and sediment collects there. They have tried various sorts of power flushing and chemicals to clean them out but found it unreliable and now recommend replacement. It's a fairly well documented problem. Even though it doesn't seem to make complete sense since air that is distributed to all vents goes over the entire core, a partially clogged core will still cause only the driver side vents to blow cold. I'm having the same problem and have verified that my blend doors and actuators are working correctly.

 

While I still think it is probably the heater core, yes you should also try resetting the blender doors. This has been discussed before but is there a thread with a discussion on how the heater core gets swapped out?

 

DavC,

I'm not saying there isn't one, just that I haven't been able to find one. I have found the procedure in the factory service manual and it doesn't appear too difficult. The passenger side interior paneling and glove box gets removed, coolant drained, a catch pan placed under the hose connections to the core and then they are disconnected. The core slides out, o-rings replaced on the hoses and the new core installed.
Land Rover Workshop Manuals > LR3/Disco 3 > 412-02A Heating And Ventilation > Heater Core Removal LHD

I noticed bubbles in my coolant reservoir tank so I am in the process of bleeding (which isn't easy on an LR3...) and I'll see if that happens to solve my problem. If not, I'm certain its a clogged core. Everything else will have been ruled out.

Best of luck

 

Cool. It should solve the bubbles at least. Easy bleed is dont touch either bleed valve or screw, leave expansion cap open, rev to 3000rpm until t-stat opens and sucks coolant in and flushes the loop, shut engine off shortly after t stat opens, let cool, fill coolant as needed, and repeat at least one more time. If you know all this stuff then just ignore me

 

Yeah thanks! I've read to ignore the bleeder valves so I will do just that. Problem is I can't find the hot level line on the reservoir... Only cold. Either way if I fill to cold I should be just fine.

 

The fill range should be two lines in the tank about an inch apart. I don't remember if one says cold or hot or if they say "fill range" or something like "cold fill range". Basically you should have coolant at least 3/4 of the way to the top line, or really as close to the line as possible but I like to leave myself some room.