Passat Air Conditioning more effective in reverse?


#1

My boss drives a Volkswagen Passat - probably not more than 5 years old, but I don’t know the exact year.

Today we were driving to our new office location and the air conditioning was working fine, but when he reversed into a parking space, the blowing was suddenly stronger AND colder. He said it’s always like that - the AC works significantly better when driving in reverse!

I just wondered what could cause this. I tried googling, but did not find anything useful. I’m hoping this community can explain it to me!

Thanks -


#2

Just a wild guess, but that would suggest that the AC is working better when the engine is revving higher. Perhaps the refrigerant has slowly leaked down. The condition might be correctable if your boss were to take the buggy to a qualified automotive AC shop for diagnosis.

Again, this is a wild guess. If your boss is happy with the way it’s working, perhaps the best approach is to accept that his AC works funny and say nothing.


#3

There could be several scenarios that might cause this but they’re pretty far-fetched.
Maybe a vacuum door issue changing its position enough to cause a difference.

Depending on the route taken maybe the evaporator is trying to freeze up. Once slowing down to approach the location it can start thawing out. That could lead to colder air temporarily and increased air flow.

Something in the A/C controls is disengaging the compressor in the forward gears (maybe short cycling?) and not so much in reverse. That could involve the PCM.

Those are just off the wall guesses that may have no validity at all.

Next time try this. Check the A/C while sitting in neutral. Shift into DRIVE and see if anything changes: car stationary of course. Then try it in REVERSE; also with the car stationary and the throttle untouched through all of this.


#4

I doubt it has to do with being in reverse. Vehicles with automatic temperature control will adjust blower speed and temperature depending on the amount of sun load through the windshield and input from infrared “comfort sensors” if equipped. As the vehicle changes direction and sun light shines directly through the windshield the blower speed will increase to maintain the comfort level.

This is more noticeable when turning corners or changing directions at slow speed like in a parking lot.


#5

^
I think that Nevada may on the right track.
When I am driving with the A/C going on a fairly high fan speed, as soon as I pull into my garage–where there is no sun–the sun sensors for the automatic climate control immediately turn the fan speed down to the lowest setting. Something similar could certainly be happening in reverse (no pun intended) to the boss’s car.


#6

I might pose this question though. The gentleman has apparently had the car for a while both at his old business and the new location.

Is it assumed by this theory that every time he backs the car up (old business, new business, grocery store, at home, you name it, etc) the sun is in the same position in relation to the sun load sensor no matter where he’s at?


#7

Maybe the Passat has a feature that puts the AC in recirculate mode so that exhaust fumes won’t be sucked through the AC into the cabin.