03 Disco heater/climate control problem
 

Hi all,
First, let me say thank you to the forum for all the help over the last two years of owning my 03 Disco. From radio and seat heater problems to cooling and vibration issues, the forum has provided what I needed to know without the need to create a new thread. Thank you!

So, my heating/ climate control is doing a weird thing. When the heater is set at a given temp in the AUTO setting, it doesn't seem to maintain it. After the vehicle has warmed up and run for about 20 minutes, cool air comes out of the front vents, warm air still comes out of the floor vents and the defrost vent. When I switch to just the front vents, warmer air comes out, but it's not as warm as the air from the floor or defrost vents. If I turn up the heat a few degrees, warmer air will blow out. It blows very warm air when set to high. It just doesn't seem to maintain a comfortable temp without starting to blow cool air after twenty minutes or so after warming up. It doesn't matter if it's in ECON mode or not.

I've run the CC diagnostic and there were no fault codes. Thermostat and upper radiator hose were replaced two months/1000 miles ago; there are no coolant leaks. I think the air was bled out sufficiently when I replaced the hose and thermostat because everything worked just great after that.

Any ideas?

Hi

When you press 'Auto' you are in 'Climate Control' mode only so when the cabin reaches the temp set it then maintains that temperature, (assuming your cabin sensor isn't blocked up with crud), this will happen as a norm unless you raise the temp of the A/C system or revert to 'Econ' mode with cabin recirc.

The temp sensor is a small/tiny fan and sensor located located to the left of the steering wheel on the dash behind a tiny grille, that's assuming you have a LHD D2. It's a common fault after 14 years of use.

That's whats confusing... the climate control isn't maintaining the temp after 20-25 minutes. This morning it's -2C, blowing snow. The CC is set at 18C. I drove 20 minutes with warm air coming out of all vents. Then, cool air started coming out of the front vents for the next 25 minutes, at a low fan speed. The interior temp slowly dropped
Until late last week, there was always warm air coming out of all vents. Once the car reached a set temp, the fan would slow; when it needed to warm back up, the fan would speed up again.

I blew the sensor fan off with compressed air. I'll mess around with it more tonight and see if that helps.

"I think the air was bled out sufficiently when I replaced the hose and thermostat because"

As you may know from reading threads here thinking and knowing you bled correctly are often two different things. These can be tricky to bleed and I say you probably have an air bubble in the system still.

I would suggest opening the bleed screw first thing in the morning (cold engine) and seeing if it is full there (highest point in system...) If not, add coolant through the bleed screw hole until full.

You may have to do this a few mornings in a row to get a perfect bleed.

I agree, it does sound like you have an airlock in the heater matrix. You will need to follow the cooling system bleeding procedure, i.e. top up the cooling mixture with the D2 facing uphill and unclip the cooling water reservoir and suspend it approx 2' above the engine or as high as possible without the cap on over night to allow the air bubbles to work their way out and then top it up. Best done inside a garage with the front end high on axle stands.

I'll park it up on some ramps in the garage tonight with the tank cap off, as well as cleaning that sensor better. Will check at the bleed screw in the morning, also. It's strange that it's been working great for the last 1000 miles, then just stopped working as I have come to expect.

Thanks, gentlemen!

Could be a partiality clogged heater core as well. I'd honestly remove the hoses from the heater core side (if they don't want to come off easy I'd cut them off and just replace it with 5/8 heater hose cut to length). Then back wash out the heater core with a garden hose. You might be surprised at the goo that could come out.

I did mine a few months ago and while it was clogged I lost maybe 1-2 cups of coolant if that during the entire process. Replaced the 5/8 heater hoses 8.00 from my local auto store, and I replaced the clamps, and topped of the coolant. Nice instant and truly warm heat.

Well, the kids had a snow day today, so I wasn't able to see if any air bled out and the heating worked as it did before. It's still up on ramps in the garage. As far as flushing and bleeding go, I'm tempted to wait a few weeks until things thaw out around here. It was -8F when I had to replace my upper radiator hose; I never want to do that again! I plan to replace all the coolant hoses as soon as it gets into the 40s or so. I'll do a thorough flushing then, as well as switch to green coolant. I rolled 150k yesterday, 15k with me as an owner. I've been fairly lucky so far, but it's time to put some time and money into my daily driver!

Keep us updated please, and you should take a look at your coolant level through the bleed screw just to find out if this is indeed the case before you tear it down for the new hoses.

Well, I drove it this morning after having left the cap off the expansion tank cap off for two days and with the front up on ramps. I opened the bleed screw and some coolant came out. Drove it for 45 minutes or so and the heat seems to be working fine again. Yahoo! Thank you gentlemen!

Given that I don't know when the heating/cooling system hoses were last serviced, I'm still planning to replace the ones I haven't already done when the weather warms up. I'm happy to know about some of these air bleeding tricks now.