Hello all, I just joined the forum as I recently bought a 2000 Buick Park Avenue Ultra and am having some issues with the climate control system. When I have the A/C running I have the classic symptom where the passenger-side vents blow ice-cold but the driver-side ones blow noticeably warmer. I removed the blend door actuator on the driver side and working the blend door "shaft" manually by hand with the A/C running I can't get it to blow as cold even with it turned all the way 'cold'. And as soon as I start turning it the other direction it immediately starts to get warm as if it's routing air from the heater core.

So this got me thinking, is the heater core "split" between the two sides or do both sides draw from a common plenum in regard to heat? Also does the system have a heater control valve which turns off coolant flow to the heater core when the A/C is running like in many other vehicles? I can feel through the HVAC box under the dash that it's noticeably warmer on the driver side.

If the only way to fix this involves removing the dash and HVAC housing assembly I'm tempted to just jury-rig a ball valve into the inlet line for the heater core like I've done on all my other (much older) vehicles because this p***es me off; a big reason I got a car like this is to have something comfy with working A/C. My previous daily driver of 10+ years is a 1993 Jeep Cherokee which didn't even come with A/C from the factory and my other 2 project vehicles don't have A/C either.

 

You can do as you see fit, but in order to fix it correctly you need to know exactly what is going on and this may involve disassembling the ductwork to confirm your theory or at least know what you are working with.. There is no comparison between a Buick and a Jeep.
Until you know exactly what is in there and if it is controlled electronically .or otherwise what you do to achieve satisfaction is up to you.
It is a luxury vehicle and has some pretty sophisticated climate control system controls.
The better thing to consider might be to get a service manual to see just what is in there and how it is supposed to work, then decide on a path to pin down just what is or is not happening.

 

That's the frustrating part, the system is very sophisticated but the quality of components leaves a bit to be desired. I did actually find an FSM online for a 2005 Park Avenue and the section on the HVAC system only outlines how to remove and replace the HVAC Housing Assembly which has all the blend doors, A/C evaporator and heater core; NOTHING about how the unit works internally or how to service it, just take out the old and put in the new. No help at all. I did take my bore-scope and feed it into the outlets for the floor ducts as I worked the controls but I could not see anything out of the ordinary; from what I could see both the driver and passenger sides were working the same. The only thing I can determine to be the problem at this point is a broken or misaligned blend air door. Since summer is starting to wind down around here I may just leave it until next Spring, I really really don't feel like tearing into it now and especially don't feel like spend money on a new HVAC Housing Assembly which I don't even know where the heck I'd find one.

Sadly it also looks like the A/C compressor is failing, had the system serviced by a shop and they said it was fine (held vacuum) but when the compressor is running it looks like the lubricant oil is leaking out the front of the clutch pulley; there's light oil stains all around that area and the supercharger belt is also oily (and there are no other oil leaks anywhere near there). I did add a ball valve to the heater core inlet line last night but it didn't seem to make a huge difference, more testing is in order though since the A/C seems to be blowing less cold each time I use it and that's 'skewing my results.'

I got this car for $1200 and am in the process of catching up on all the maintenance. Just ordered new spark plugs and plug wires and I also need to change the supercharger oil and coupler as well as the front motor mount; already got the engine oil changed, partial flush (drained and filled) transmission, new steering tie rod ends, new rear toe arms, 4-wheel alignment, new front brake rotors. Not to mention the stupid front seat tilt motors are broken (busted gears, apparently common problem) on both seats for both front and back of the cushions, ughh. I would honestly prefer all that interior stuff was simpler analog/manual control as I'd be able to fix it, or better yet it would probably still work! lol...

 

Not sure where you can obtain a control assy , but it does sound like it is malfunctioning..

You might want to be careful with any kind of flushes because,,,,,,,,,,,,,,,,they stir up accumulated crap , but do not get it all out and now it is circulating throughout the system.