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Hot on one side, Cold on the other

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cold hot side
168K views 102 replies 30 participants last post by  mylife1903 
#1 ·
Had a new issue pop up today. Felt like it was just not cooling the interior well and it's not hot out yet. Was a bright sunny day so the interior was a little warm put the A/C on and took off. When it felt like it wasn't cooling well I turned the temp down and felt cool air coming out my vents this was all till I put my hand over the right side center vent and felt HOT air coming out. So turned the temp down all the way on both controls. Left vent cold air, left center vent cool air, right center vent hot air, right vent hot air. Adjusting right side temp control cold to hot does not change the temp of those vents, hot all the time. Change the temp on the left side control to cold and cold air comes out of left side, turn it to hot and hot air comes out left side. FSR, maybe?
 
#3 ·
That's what I was afraid of. I know the P38s used to have blend motor issues though mine never did. Totally different vehicle but I wonder if there could be something there. Hopefully someone else has had this issue and worked through it.
 
#4 ·
Probably a blend flap failure. It's different from the P38 but same principle. Could also be the heater valve itself having a fault or restriction. Feel the coolant hoses coming out of the valve (valve is over on pass. side near inner wheel well I think) and see if it's hot. If the hoses are hot, your problem then most likely lies in the under-dash components.
 
#7 ·
Hi,
Had the same problem and nothing shows on the computer set up.
I took off the valve on the passenger side of engine bay (basically a 3 port valve switched by demand) and dismantled and cleaned it out. Bits of crud had gathered and made the valves stick. Had no problems since.
 
#5 ·
Doubt it's the heater valve. I have cold air coming out the driver side vents but very hot air coming out the passenger side vents. A/C control? maybe? I sure hate to deal with probably's on these vehicles, just end up replacing unnecessary parts, oh wait, that's the stealership's approach.... and they are "trained" on these things....
 
#6 ·
Hooked up the All Comms this evening and ran a check on the HEVAC system. The only error it pulled was "Air Quality Sensor Line Fault". I cleared the system with no change in the issue and read the faults again and the same error came up. Could not find anything online relating to this error. Also does not even seem to relate to the issue? Has no one had this problem on a MKIII but me and 1Star2 ??? Sure hope to fix this before the hot weather starts coming which seems to be right around the corner. Going to be in the mid 80s tomorrow. :rolleyes:
 
#8 ·
Thanks G8HAV. So you had cold A/C air coming out the vents on one side of the vehicle and hot air coming out the other side? Think I know the valves you are talking about but they are on the driver side for me. :mrgreen: I would have thought those valves just supplied hot air to the whole system or blocked it as needed. Trying to figure out how they would allow hot air to come out of only the passenger side vents (driver side for you).

When you say you dismantled and cleaned it out are you talking about taking the 3 port valve assembly itself apart and cleaning the parts inside valve or just the connector? Can you describe this process a little more and possibly what you used to clean it. Just trying to visualize it from the office before I start taking things apart and make sure I will have what I need ahead of time. Thanks again for the input.
 
#12 ·
The HEVAC system on the 03-05 is pretty complicated, with 53 pages (10%) of the RAVE Workshop manual devoted to this system.

Since "hot" and "cold" are relative terms, have you actually measured the air coming from the vents? Is "hot" actually just non-cooled air or is "hot" heated air, and vice-a-versa depending on where you are and what the temp is outside. For example, here in Houston right now "hot" area would have to be somewhere above 80 or 85 degrees since that's the high temps for the day.

Assuming you have the "highline" version (which that's all I've ever seen in these, but apparently there is a less sophisticated "lowline" version) you might consider looking at the two temp sensors and swapping them from one side to the other. If the "hot" and "cold" sides don't change, then it's not the sensors.

Do you get any change if you enable the Max AC switch? This should override most of the sensors to cool the truck as quickly as possible and doesn't shut off until you shut it off.
 
#13 ·
Still no resolution here.

The right side is only HOT air, meaning turn the right side temp control knob to any temperature and the right center and far right vent only blow the hottest air possible no matter temp outside, inside or whatever temp setting you have it on the right side control knob. The right side vents only blow one temp, as hot as the engine/system allows the heater to blow. Set your temp knob all the way clockwise to full heat and that is the temp my right side is stuck at. Maximum heat setting is the only temp that comes out of those vents. Turn the temp control knob on the left side and the temp adjusts as normal in the full range of cold to hot according to what you set the control temp knob to. Pressing Max A/C button works for left side vents but the right side vents only blow higher fan speed but still max heated air, no drop in temp on right side vents from full heated air.
 
#14 ·
Since there is no change when you set the Max AC (I assume you have it on level two which manually overrides basically all of the valves, sensors and flap settings), it seems to point to the coolant valve.

When you set the ATC ECU to a temp, the ATC ECU reads the temp from the appropriate temp sensor and closes the appropriate coolant valve as necessary to that side of the truck. Enabling the ATC ECU Max AC on level 2, the temp sensors are bypassed and the ATC ECU closes both coolant valves. Since the Max AC switch is separate from the ATC ECU LH/RF switches, it appears the problem is related to the coolant valve.

I believe if the temp sensor was bad, grounded or shorted, it would default to blowing super cold (thinking it's 131dF).

This is just an educated guess considering the symptoms.
 
#15 ·
Thanks LEBoyd. Now we are getting somewhere. That is making a little more sense. I thought the valve under the hood on inner fender, I believe it is on the drivers side for US models, just turned the flow of hot air to the HVAC on or off. I did not realize that that was where the left and right sides are separated where temperatures are concerned. G8HAV mentioned something earlier but I did not follow that as I thought it was one in and one out for hot water flow to the fan/blower coils to supply heat. Tried to get clarification but did not hear back. He also mentioned about cleaning this valve system but no real detail as to what he cleaned. I am assuming he took the valves apart and was not referring to cleaning just the electrical connectors. I tried that and did not make a difference. Guess I'll pull the valves off and see how they come apart. If anybody has any experience with these valves and the inner workings I am all ears. Thanks for the help.
 
#16 ·
Take pictures :)

I found one at http://www.autopartstrader.co.uk/details_popup.php?descript=2001%20- 2009 L322 Coolant Valve Block&sh_code=cw01&uniquen=280613&searchID=22340418&model_l=RANGE ROVER&manu=LANDROVER&ic_num=258&pdesc=MISC &pyear=2001

for 250sterling. You might contact them for pics to see if it matches and maybe order it *before* you tear yours apart :) That way, if you are successful you can sell the extra one here or on ebay, and your truck won't be down for very long.
 
#18 · (Edited by Moderator)
Generally, when the thread dies the person either fixed it with the last recommendation or they took it to a dealer who fixed it. They just don't think about following up for everyone.

Since you have the same symptoms (and I assume you've run the tests I recommended), then I make the same recommendation. I would like to hear whether it works :)
 
#19 ·
Since you have the same symptoms (and I assume you've run the tests I recommended), then I make the same recommendation. I would like to hear whether it works :)
I haven't had time to start the troubleshooting yet (Just finished the "transportation mode" fix :?). I decided to check here first for suggestions before I dig into this issue.

When I read this thread it sounds like the conclusion was to check the coolant valve first?. I've based that thought on comments by you, G8HAV and ringoP38.

Now, I need to find time to figure out what the valve looks like so I can find it.
 
#21 ·
You need to find the RAVE manual online and download it.
Absolutely! The RAVE manual should always be the first stop in researching any issue, procedure or curiosity for pre 2006 rigs. Once you understand the correct operation and a proper repair procedure you will much better a short cut posting or description here.

http://www.landroverresource.com
 
#22 ·
While I haven't started the repairs yet (still not sure where I want to start), today I checked temperatures. My "sketch" is of the dash vents as you sit in the car. The lower row is the back AC vents. The temperatures are in Fahrenheit. The settings were as cold as the dials will allow (60 degrees) and the fan speed was two lights. There definitely seems to be an issue on the right (passenger) side of the car. I also think the volume of air is less on the right side.

PS got the RAVE, thanks for the suggestion.

Text Font Line Pink Handwriting
 
#23 ·
Coincidentally, I just developed a similar problem on my 2006 this weekend. When I turn the temp down to its lowest setting, I get semi-cold air coming out of the driver's side far left vent, lukewarm air coming out of the left/center vent, and warm air coming out of the right/center and far right passenger vent. Strangely enough, I get scorching hot air coming out of the rear seat passenger vents even if the dial is set to cold.

I don't think that this would be a coolant valve issue since the system is sending scorching hot air to the rear seats. Any ideas?
 
#25 ·
1star2,

I have not had time to work on my issue. However, it is interesting that shortly after my problem began the fan blower started running on "max" most of the time. And the fan speed controller does not work. I think that is an issue associated with the "final stage resistor". I have purchased the resistor but have not had the time to install it. I would be ecstatic if I installed it and the heat/cold problem went away. But I'm not hopeful. It appears you replaced the resistor too. Did your fan go crazy after the hot/cold issue? And did the resistor fix the fan issue?

Do you have colder air on the left (drivers) side only?

My gut tells me it is a blend door issue. Perhaps associated with the center hot/cold wheel below the center vents?

I see you are in Denver, I bet you wished you had gotten your's fixed when it was cooler. Not a good time to have your AC go out, huh? (for the rest of the world, we are having temps in the 100 degree Fahrenheit and above range.)
 
#26 ·
Larry

I didn't have a problem with the fan speeds, just replaced the FSR hoping it would fix the issue with the passenger side AC not working.

The AC works on the driver side vent and the left center vent, however I have noticed lately that the left center vent doesn't seem to get as cold as the driver side vent.

Yes the weather here in Denver has been ridiculously hot these past few days, fortunately I have another vehicle that I drive daily with ice cold AC.
 
#27 ·
So 1star2, (I bet you have a real name....). I had to replace my final stage resistor. I was hoping that would fix the problem; but deep down I knew it wouldn't. My "deep down thought" was correct. My fan now works perfectly, my "cool" doesn't. There seems to be plenty of forum subscribers that have this problem. I am surprised we haven't had a clear indication of what is wrong. We did have some suggestions, but they were more toward "thoughts" rather than a clear fix. Whatever it is, you and I have the exact same issue.

Oh my how I wish the weather temps would moderate. I think today broke the all time record for consecutive days over 100 degrees. In my area of Denver 101 degrees F.
 
#29 ·
I have this same problem in my 2006 Supercharged, but after a few days of driving with it I've noticed some distinctions.

If the car is cool (in a garage) before driving, the AC will blow fairly cool into the car while driving. Driver's side still gets slightly cooler than passenger side.

If the car has been sitting in the sun, the driver's side blows fairly cool air but the passenger side blows warm air even with the temps turned down to the lowest setting. The interior never seems to cool and the AC doesn't seem to be able to overcome the heat in the car.

Now, if I drive for MORE than half an hour with the A/C on, (when the car hasn't been sitting in the sun) the passenger side will slowly start to warm up while the driver's side keeps cool. Also, the rear vents will start to blow hair-dryer hot air no matter which setting the dial is on. I also noticed that the tunnel between the seats starts to get very hot if I'm driving for more than a half hour at highway speeds/RPMs.

I'm going to first try topping off the refrigerant. When the AC system button is turned on, it sounds like air filling a balloon occasionally. Maybe the system is low on refrigerant and that's what's causing the issue. I'll let you know what happens after topping off with Freon.
 
#31 ·
If you want to be 100% sure of the problem before you put a new valve on it, then your next step is to remove the dash. Once the dash is out, you can start playing with the system, vents, etc. and figure out whether the temp coming to the blower and vents is different or if the blower some how is affecting it.

I am interested in your numbers on the temp. 85d outside and 22d blowing out of any vent would be pretty amazing! That's a 63d cool down. There are not many compressors designed to produce that type of cool down. Generally and good working system would be 20d to 25d less than the outside temp (like you show on the right side - 60d).

I don't have the problem, but I am interested in how it goes in dismantling the dash and what you find as the problem.
 
#32 ·
I have the exact same sypmptoms, with the exception of the sounds. And maybe the only reason I don't know about the sound is my ears.....:smile:
 
#33 ·
So I have the same problem with my 2006 HSE. Closing the passenger vents sort of eliminates it.

I have a feeling it's the climate control valve - aka one side is stuck open. The Jags do this all the time, as did the BMW's of similar vintage.

I have to check it out and see.

Please let me know if anyone has found a solution.

Take care,

George
 
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