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The center AC vents now blow left side cold, right side warm.
Mine does the same. I ended up doing basic detective work, but have not gotten around to fixing it. The system has 2 blowers. I ended up unplugging the fuses for the blowers, one at a time (driver side door jamb/facia). The driver side seemed fine (the cold side), but the passenger side seemed "blocked". The blower works (motor ok), can be adjusted for speed (resistor/transistor ok), the fresh/recirc works, but the air flow sounds different. It sounds like there is an obstruction of some kind in the duct between the blower and the air box. Or is it a leak? The next step I believe is to remove the glove box and follow the noises.
In the meantime, I refilled the system with a cheap gauge/can from the parts store. It restored the cooling ability on the driver side (ice cold), but the passenger side is still warmish.
There is a PDF around that can guide you through running the diagnostics from the control panel. It can show codes for specific errors. It did not point me to anything. The asymmetry is the symptoms steers me away from individual sensors, etc. It has to be related to the passenger side blower and duct. Let me know if any of this makes sense, and what you come up with.
Checked codes. There was a 23 and 44. I cleared those as I don't know there provenance and they have not returned (showing 0). I assume if these were still issues these would be rethrown?
FWIW, when that happened on my truck, I had a freon leak. As the gas dissipated, the vents became as you described.
Changing the hose and new freon was the fix.
If there are two blowers, one for the cold deck and one for the hot deck, then the air has to be 'mixed' at some point to reach the desired temperature ranges in-between Maximum A/C, and Maximum Heat settings. Is there not a 'Damper Mixing Door' further inside that should close off completely, one way or the other, if you want only the coldest, or hottest air possible, and bypass this mixing box? If this Damper Door sticks in a partially closed/opened position, the hot deck air will bleed into the system in Maximum A/C mode, when it should be completely closed off, introducing the warmer air.
If there are two blowers, one for the cold deck and one for the hot deck...
There is one blower per side, one driver side, one passenger side. Each one pushes air into the main box. The air then flows over the A/C evaporator, then the heater matrix. From there, there are flapper doors that direct the air around to the various outlets. The thing is that those flapper doors act on the entire air flow as they are across the entire air box. There is no left or right flapper. So, the armchair analysis suggests that the right/cold, left/warm is somehow caused by the separate feeds not doing the same thing. This is sort of confirmed by turning each blower off individually (pulling fuses) and listening for air flow. Driver side is plentiful and quiet, the passenger side is weak and noisy. Time to open this up, I suppose...
My 2004 XK8 has just started this activity this summer, and after having read all of the above investigations and trying all of the suggestions I tried something else and think I may have found the cause.
My Canadian car never sees winter so very rarely has the heat on and when the nice weather is here it is mostly top down so my AC/Heater system does not see a lot of activity or cycling if you will.
I cannot explain the difference between left and right sides having a temperature difference, but they do, even when I cycle through all the different vent combinations, i.e. floor to dash.
What I did was clamp off a hot water line into the heater core at the firewall. As soon as I did that, I could feel the temperatures cool down and equalize on both sides of the vents. It seems to me then that the hot water control valve is not functioning. Probably stuck somewhere in the middle.
I guess my next step is to take out the valve and see its condition. Will try to repair if I can and if not replace.
Photo attached of where I clamped the hose.
I cannot clearly see this in the picture, but there are 2 hoses to the heater core. One is just a hose, the other one appears more kinked due to a (I am guessing late) addition of a one-way valve. That one-way valve is supposed to prevent the flow of hot water to the core during the use of the A/C. Double check you even have this valve. The combo hose/valve is cheap and easy to replace if needed. That system is somewhat complex, sort of hard to reach and therefore hard to properly debug. Best is to feel the hose temperature with your hands to see if hot water is actually flowing to the core. To my knowledge, any heat/hot water going to the core will easily beat/win over any attempt to cool with A/C.
While you are there, you might want to do a nice heater core flush/clean to restore proper heat transfer and enjoy the benefits of that low volume/high flow design.
As a data point, the water valve defaults open, i.e., disconnecting it from power leaves the valve wide open, and brings the inside temp to a crisp.
I used a vice grip with flat swivel ends on the hose to as not to damage the hose. The hose I crimped off was hot although I can't be sure if it is the in or the out. I do know that the water to the heater core is just scavenged off of the cooling system water with the small circulating pump so this should not affect the engine cooling system. They sure make it complicated don't they.
I have had this car for 10 years and part of my routine maintenance is a heating system flush every 3 years. I have only put 80,000 kms. on her in 10 years so I try and make up for the lack of use with increased maintenance.
09-08-2016, 12:20 PM
AC blowing half cold/half hot
