Cooling of a different sort

[Kristuphir]

While I'm chasing down my phantom cooling issue, I've got a completely different "cooling" type of question.

Now that it's finally warming up in Southern California, I'm using the A/C on my new 535im. It blows cold and works great, but every time i let off the gas, even a minute amount, I hear a hiss, or "shhhhhhhhhhhhhh" from the HVAC system. What is this? It sounds like pressure being slowly released from somewhere, which doesn't strike me as a positive.

[632 Regal]

check all your vacume lines, probably have a leak somewhere.

[Kristuphir]

Wouldn't a leak that audible make the car run like crap? This is only when the A/C is on. Or does the A/C have a vaccuum system of its own, or something?

[joshua43214]

The DME will compensate for small vacuum leaks.

I can't remember if the 91 models has any vacuum powered flaps, maybe the recirc flap?

Definately sounds like a vacuum leak from behind the dash though, drop the glove box and the drivers hush panel and peer up in there with the engine running and see if you can spot something. Pop out the radio and look in there too.

[Alexlind123]

Wouldn't a leak that audible make the car run like crap? This is only when the A/C is on. Or does the A/C have a vaccuum system of its own, or something?

That exact same thing happened to me when i have the A/C on. Im not sure it on throttle lift tho...it seems rather random. It seems to be doing it less now that i have bene using the A/C for awhile.

I will post and update if anything changes.

[liquidtiger720]

Mine does it tooo...randomly

[Alexlind123]

I think its normal. At first i thought it was something common only to r12 systems, but if you '95 does it...then i duno.

[BillionPa]

i think the sound is actually the compressor "decompressing" through a valve or something

[fujioko]

My 92 525 makes random noises when the heating is on. I spent a little time chasing down the noise, then I realized the car has climate control. The heating system is actively adjusting the climate in the cabin.

Try this.. Set the temp to 80 on a cold day. After about 5-10 min the climate control will start leveling out the cabin temp and the HVAC system will change sounds and the air temp out of the vents will get cooler. Magic!

If you owned a chepo car like my Saturn and set the temp to full “RED” then the heater will pump out hot air until the cabin becomes uncomfortable. No climate control, therefore unregulated temp.

That’s my 2 cents.. I could be wrong

[Alexlind123]

My 92 525 makes random noises when the heating is on. I spent a little time chasing down the noise, then I realized the car has climate control. The heating system is actively adjusting the climate in the cabin.

Try this.. Set the temp to 80 on a cold day. After about 5-10 min the climate control will start leveling out the cabin temp and the HVAC system will change sounds and the air temp out of the vents will get cooler. Magic!

If you owned a chepo car like my Saturn and set the temp to full “RED” then the heater will pump out hot air until the cabin becomes uncomfortable. No climate control, therefore unregulated temp.

That’s my 2 cents.. I could be wrong

Yep, even the HVAC with the knobs and dials instead of the rollers is thermostatically controlled.

[Kristuphir]

Yep, even the HVAC with the knobs and dials instead of the rollers is thermostatically controlled.

That's the kind I have. Yes, the heater will make its shifty little sounds as it figures out what to do. It just seems like the A/C noise is a little loud to be normal. On the other hand, it's the first car with working AC I've had in a while, and it's starting to get warm. Maybe I should concentrate on the things that DON'T work for now...;)