Uneven A/C Temp at Registers

[chrism]

2003 V70 Base....

When running the A/C, I'm getting somewhat warmer air out of the passenger side registers than the drivers side. Both control knobs are turned to the blue dot. It does this whether the air recirculation button is activated or not. Regardless of where I set the temp control knobs, if they are set to equal numbers, the RH side is always warmer. I'm suspecting there is a damper door somewhare that is not functioning fully one way or the other.

So.... now for a couple questions:

Can I swap control knobs left-for-right (or swap their wire leads) to verify that's not where the problem lies?

Do these cars have a heater control valve in-line in the hot water supply like the RWD's, or does the heater core continually flow hot coolant with cabin temperature being controlled purely by the dampers?

Where would I find the damper(s) that may be the culprit(s)?

Where do I start?

[jimmy57]

The leads to doors can't be swapped, the motors run reverse direction and the CCM ID's the dampers on the 05 and later so you can't change the damper motors without a VIDA or other tool commanding the ID action to occur.
IS the temp even when a/c is off ?
The coolant flow is continuous, no shut off valve.
Low refrigerant causes uneven evaporator temp and can cause what you are experiencing. If low refrig is the cause then the temp will be the same on full cold with a/c compressor turned off.

[chrism]

The leads to doors can't be swapped, the motors run reverse direction

I don't mean swap the polarity to the motors, I just meant to swap the control switches left-for-right to see if the problem follows the switch (which I doubt).


...the CCM ID's the dampers on the 05 and later so you can't change the damper motors without a VIDA or other tool commanding the ID action to occur.

If I have an 03, does that mean I'm exempt from that rip off game?

Is the temp even when a/c is off ?

I believe it is, I'll verify the next time I'm in the car.

Low refrigerant causes uneven evaporator temp and can cause what you are experiencing.

I connected a cheap recharge kit to the low pressure fill port and found it to be running at about 70 psi ON THE LOW PRESSURE SIDE!!! I bled some off to where it now runs somewhere aroud 45 psi on the low side - right where el cheapo refill kit says it should be. I don't have a guage to measure the high pressure side, but since I can see the low pressure side drop when the compressor clicks on I assume proper compressor function.

If low refrig is the cause then the temp will be the same on full cold with a/c compressor turned off.

I can definitely tell when the A/C is on - cold air coming out of the vents (just colder on the LH than the RH).

[jimmy57]

The left and right controls are not serviceable. Made onto the circuit board within the CCM.
04 and earlier do not have ID's dampers but changing damper motors may or may not work. 1st version works by step counting. IF you take it apart and the door stays in EXACTLY the same spot when motor is put back then it needs no calibration. If it was at step 44 when you pulled it apart and it goes back in step 72, the CCM will move the door to the previously calibrated end point step number and when it needs to go back to the other end position and stops at step 28 when it should go to 0 it will set a damper motor code.
45 is not correct pressure for a TXV regulated a/c system. TXV systems can't be charged very effectively with gauge pressure. A properly charged P2 will have 22-26 psi when engine is running at 1500 RPM and system stabilizes @ 80F or thereabouts. Fan needs to be on next to highest position. THis will be the pressure just be fore CCM cycles compressor off due to low evap temp.
If you want an automobile that requires no scan equipment to diagnose and repair you are going to have to get something way older and far less equipped.
Cheap new cars have gone to electric damper motors and have systems that can't be diagnosed properly without computer tools.

[chrism]

As it turns out, I took the car to my local Volvo independent shop for help. They found the charge to be "slightly" low, but the main problem was that the radiator fan was not kicking on as it should. He said the engine temp started to spike while they were running it in the shop. Scanning the car with Vadis (or actually he said the new tool that replaces Vadis - I can't remember what it's called) detected a bad control module on the fan - probably a bad solder joint???? Anyway, the fan, shroud, and controller come as a unit, so I paid some $'s to get it replaced. A/C works great now with even temp out of both LH and RH vents. So the bottom line is that either a low charge or poor condenser cooling can cause the evaporator to chill unevenly side-to-side.