A/C issue - Not DCCV - Cold Air Left Side/Warm Air Right Side

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Doctor_Wu

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Oh ye masters of the LS... I seek your wisdom again. I have read several threads on the issue of A/C problems and see many posts on the DCCV along with the DATC... more on that in a moment.

I have a 2000 LS V6...

I have cold air coming out of the drivers side and hot air out of the passenger side.

To be specific the A/C is blowing 50 degree air out of the far left (driver side vent) vent
57 degree air out of the middle left vent
67 degree air out of the middle right vent
69 degree air out of the far right (passenger side vent)


All fuses are good. (Not sure about relays... do they fail 1/2 way?)

The DCCV has been replaced in the last 12 months to fix a problem with the heater last winter.

I have used vice grips to clamp off and block any water flow from both sides of the DCCV to the heater core

I do get a fault code of 12 42 on the DATC self test and that reputed to be a failure on the recirculate air door. In turn, I have closed the recirculate air door so no outside air can enter the car... and it's still cold on the left and warm on the right.

The AC compressor is running and does not cycle off.


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In other threads I have read several accounts of such failures, and several "solutions" mentioned.

Saw one person claim to have resolved this via turning the fan speed to max, then cycling the temp all the way to 90, then back down to 60, tried that and it did nothing.

Have seen a couple of people mention getting a new DACT unit, even buying one from a junk yard... and that fixing it.

Have seen at least one person mention the interior temp sensor (some reports indicate there are 4 sensors total)...

Have also seen a mention of a loose pressure switch causing problems.

----

Is there a definitive fix for this failure... or a way to escalate the trouble shooting...?

Any advice or accounts of similar failures and subsequent repairs would be appreciated.

TIA,

DW
 
I had a similar problem and it was my heater control valve but I have a V8. Sorry don’t remember how much it was but I did go through the dealership so it wasn’t cheap.
 
I have the same issue. I tried to get it checked out but when I took it in, the guy said it had to be blowing hot air for him to check it. It blows cold air 99% of the time so i guess I have to wait until hot air blows constantly. I have a 01 v8 by the way
 
I don't know why you say it isn't the DCCV. It is the only thing that can cause a temperature difference from one side to the other. Also, 50 degrees is still too warm, unless it is 120 degrees where you are.
 
The problem with my A/C wasn’t the DCCV it was the Heater Control Valve. I had the same problem this guy is having hot air from one side of the car cool air on the other.
 
Lucky_Ls said:
The problem with my A/C wasn’t the DCCV it was the Heater Control Valve. I had the same problem this guy is having hot air from one side of the car cool air on the other.
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Lucky,
The DCCV (Dual Coolant Control Valve) is what you are calling the "Heater Control Valve."
 
joegr said:
I don't know why you say it isn't the DCCV. It is the only thing that can cause a temperature difference from one side to the other. Also, 50 degrees is still too warm, unless it is 120 degrees where you are.
Click to expand...

B/c we have clamped off hoses on both sides of the DCCV (one and then the other), to prevent water flow to the heater core and there's no change in the temperature across either side of the A/C vents. Still cold on left/warm on right. Shouldn't you be able to eliminate the failure via this process?

Plus, after the unit is off all night, the water in the cooling system in the engine is at ambient temp, and immediately on start up and turning the A/C on, the left side is immediately cold, and the right is immediately warm. They are noticeably different. It should take at least 5 or 10 minutes before the water in the heater core is warm enough to effect the temp of the A/C.

Beyond that... the DCCV is new, and others have had similar problems even after replacing the DCCV... I saw one person mention how they'd replaced theirs twice and still had that problem.
 
Me too!

Dr Wu, I am having the exact same problem! I just replaced the DCCV today, and the pass side is about 10 degrees warmer. Can anyone help us out?

Thanks,
Frank
2000 LS V6 Sport
 
If your A/C is not cycling on and off you're low on coolant... Charge up the mof and you should be good to go. This was happening to my car this last summer, I half-a$$ed re-charged it and it still didnt do anything. Had my uncle whip out his tools for doing the job instead of that BS hose on a can crap. Sucked in an entire can of R134!!! Runs like awesomeness now. Our systems run differently than some, they run 100% all the time, and cycle on and off. To warm up the air the cold air passes through the heater cores. If your A/C is not cycling, there is not enough pressure to cycle off, so it will keep running until it reaches proper operating pressure and turns off. You probably will get better mileage when its starts to cycle too.

Recharge it, and do it proper, get a mechanic to do it, or find someone with actual hoses, the "Do it yourself" hose on can is total JUNK
 
I clamped off both hoses as well and I still had the heat of hell blowing out of the vents no matter where the temp was set. I replaced the DCCV and all temperature problems were solved.

Possible your DCCV is malfunctioning again.
 
De-marko said:
I clamped off both hoses as well and I still had the heat of hell blowing out of the vents no matter where the temp was set. I replaced the DCCV and all temperature problems were solved.

Possible your DCCV is malfunctioning again.
Click to expand...

Agreed. Just because you replaced it a year ago doesn't mean it could not have failed again. Unlikely, but not out of the question. There was a bad batch of thermostats that got out a few years back also.
 
Dccv

Sounds like a DCCV problem to me too. If you take off the power to the DCCV then both vents will blow hot. If your anitfreeze is too heavy it may affect the DCCV performance. The DCCV is a simple spring loaded solenoid. If some gunk getting embedded in the spring or the solenoid goes bad, then you will get some strange results.
 
I have the same problem once in a while. If i turn the car off and then turn it back on it will be fine.
 
Doctor WU--I feel your pain, I really do. I replaced my DCCV 2 years ago because of passanger side blowing heat. Most of us know what a pain that process is. Six months later the passanger side again blew hot air. Maxx warrantied the part, and the new DCCV did again fix the problem. About a month later, I get the same thing only the passanger side blows warmer air not hot air. I bought a used DATC module off of ebay, and poof everything was working fine again. Then a few months after that I get the same freaking thing again. That is where I am at now, and it is really annoying. I would really like to know if something else causes this too!

Oh yeah, I get the same thing also--warmer air on the passanger side even before the engine coolant heats up.
 
scjmc said:
Doctor WU--I feel your pain, I really do. I replaced my DCCV 2 years ago because of passanger side blowing heat. Most of us know what a pain that process is. Six months later the passanger side again blew hot air. Maxx warrantied the part, and the new DCCV did again fix the problem. About a month later, I get the same thing only the passanger side blows warmer air not hot air. I bought a used DATC module off of ebay, and poof everything was working fine again. Then a few months after that I get the same freaking thing again. That is where I am at now, and it is really annoying. I would really like to know if something else causes this too!

Oh yeah, I get the same thing also--warmer air on the passanger side even before the engine coolant heats up.
Click to expand...

If you are having rapid repeat failures of the DCCV, I would check the reservoir cap. If it allowing the cooling system to pressurize to more than 16 PSI it will cause DCCV damage, and sometimes waterpump damage.
 
joegr said:
If you are having rapid repeat failures of the DCCV, I would check the reservoir cap. If it allowing the cooling system to pressurize to more than 16 PSI it will cause DCCV damage, and sometimes waterpump damage.
Click to expand...

Thanks for the info, I will pressure test the cap as a precaution. It is the origonal cap from 2002.
 
This happens to me occasionally and I have always chalked it up to the blend door getting stuck. To fix it I cycle the temp on the left side all the way up and the temp on the right all the way down, the vice-versa. This causes the door to cycle all the way from one side to the other (I believe). I can hear the door moving. After this process I go back to the temp I want and all is good. It happens about once every two or three months.
 
rainjacks said:
This happens to me occasionally and I have always chalked it up to the blend door getting stuck. To fix it I cycle the temp on the left side all the way up and the temp on the right all the way down, the vice-versa. This causes the door to cycle all the way from one side to the other (I believe). I can hear the door moving. After this process I go back to the temp I want and all is good. It happens about once every two or three months.
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The LS doesn't have a temperature control blend-air door. You must have a gen I LS. The gen I LS does have a "cold air bypass" door. It is only used when you need maximum cooling on both sides. It can't regulate temperature. The DCCV does that. It sounds like you have a bad DCCV. The bypass door is not getting stuck, it is opening like it is supposed to once the car reaches the correct temperature. At that point it is not supposed to close back, the DCCV is used to regulate temperature.
(Gen II does not have a bypass door.)
 
Problem resolved...

You were correct Cracker Jack, and joegr was right about how 50 degrees was too warm.

We now have 45 degree air out of all vents.

The system was low on Freon -- we recovered all the freon, then charged up from empty. I guess the evaporator was getting enough Freon to cool the first few inches of the coil but the Freon had boiled off completely before it could cool the part of the coil that cools the right side of the car.

Some of the posts I read suggest swapping the temp sensors to see if that made the opposite sides cold and hot - but the temp sensors as I understand only make the fan speed increase when the ac is on AUTO.

This system has a self diagnostic that will self test all ac doors and thermostats. The self test is well known, but just in case people are unaware it's - key on, press OFF and FLOOR at the same time and then press AUTO within 2 seconds.

The system will self check 25 points and then give you any fault codes that it finds (any open or shorted temp sensors would show up during this self test) Fault codes are 4 digit numbers (1251 is the in vehicle temp sensor circuit open) -

Also if one side or the other vents blow hot or warm air - and it is caused by the DCCV, clamping off the heater hoses at the DCCV should allow the system to blow cold until you remove the clamp from the hose. And as it takes a few minutes for the water to get hot (after sitting all night) the ac should blow cold out of all vents within 2 or 3 minutes of start up - then as the engine comes up to operating temp - if the DCCV is allowing coolant to flow to the heater core that side would warm up. Hope this helps.

Thanks to all who contributed. Wish I'd tried this simple fix when it was actually hot, but we were put off of low freon as the failure by vacuum pressure readings that were within range.
 
Doctor_Wu said:
...Wish I'd tried this simple fix when it was actually hot, but we were put off of low freon as the failure by vacuum pressure readings that were within range.
Click to expand...

For anyone else that maybe going through this... Never take the shortcut of just checking the low side pressure. You have to check the low and high side pressures and compare them to the service chart based on exterior temperature.
 
joegr said:
For anyone else that maybe going through this... Never take the shortcut of just checking the low side pressure. You have to check the low and high side pressures and compare them to the service chart based on exterior temperature.
Click to expand...

Checked both, but did not have access to a service chart that I was aware of.
 
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