A/C power drain

[Orion]

Hey all,

I took my '02 WRX in today because for a few weeks now whenever the air
was on, there was a noticable thump and loss of power whenever it cycled.
When the A/C is on, this is astoundingly worse, a loud "chirp" accompanying
the (much more severe) power loss. The car has not stalled, but it almost
has once because I went when the A/C cycled. The first time I asked, they
said it is completely normal, expecially between 10-15 thousand miles (which
I'm not in at the moment anyway). They said it was normal for new car
break-in. The second time I called and talked to a different person, they
said that they can't reproduce it (which is a blatant lie, unless they
didn't actually turn on the A/C). I'm taking them on a test drive tomorrow
to see what they say, but wanted to know, is this "normal" for the WRX? It
happens every 15-30 seconds when A/C is on, whenever it runs its cycle.
Hasn't happened before this, and is a big bit of discouragement.

Any comments or ideas?

Orion

 

[SuperPoo]

Hey Andrew,

I have been running my AC a bunch lately-- I do notice when it cycles on and
off but the effect on performance is minimal.

Sounds like you are being fed a load of crap. My WRX now has about 17k, so I
have just been through the mentioned 10-15k-- I have noticed no difference
from 100 miles to present mileage in AC or motor performance.

Did you get that new ecu?

Steve

 

[Carl 1 Lucky Texan]

Yeah - tell them one of 2 things; "If they all do it - give me the keys
to....that one and lets take a drive!"
or
"If they all do this then they are all broken and they should all be
fixed and you can start with mine!"

Carl
1 Lucky Texan

 

[Ian Firth]

I took my '02 WRX in today because for a few weeks now whenever the air
was on, there was a noticable thump and loss of power whenever it cycled.

Mine does the same thing, and it's very noticable at 5,000 feet below
3,000 RPM. If I don't keep the revs up letting the clutch out the car
will not pull away from a stop without almost stalling.

It's normal for an engine this weak at low RPMs.

 

[Orion]

I appreciate the inpute on your experience, Steve, and have a bit more
confidence going back and telling them they're full of it (as I originally
intended). I do really like Carl's idea of having them show me on other
vehicles on the lot.

I don't think it's the low-torque at low RPM's problem that Ian was talking
about. I've become quite adept at my Rex and while I know they're a bit
feeble before getting on the turbo (not that bad), this is nothing like
that, and it only happens when the A/C cycles. It just happened to be that
once while left turning in front of on-coming traffic that it cycled right
when I needed the damn power.

As for the ECU, not yet! I have gotten all other parts (they're going in on
Saturday, so wait for the post on how it went). A week and a half ago they
called me to check my card number, telling me everything was ready
(specifically said "we got the core and remapped it") and 2 days later I got
everything...but the core. I called them (today, actually) and they said
that they didn't have a core, and actually asked if I could send mine.
Uh...no, I need the car. When I explained that they told me almost 2 weeks
ago it was good to go he appologized and said he'd check into it with "Ken"
and to check back tomorrow.

On the plus side: no core cost above stage sub-zero, so listed price doesn't
have the "+ core" cost. Wee!

Thanks again for your input, guys. Any more thoughts are still welcome.

Andrew

 

[John A. Mason]

This is never a normal situation for a car!
John

cycled.

Mine does the same thing, and it's very noticable at 5,000 feet below
3,000 RPM. If I don't keep the revs up letting the clutch out the car
will not pull away from a stop without almost stalling.

It's normal for an engine this weak at low RPMs.

 

[Ian Firth]

This is never a normal situation for a car!

An A/C compressor can suck 20% of the power from an engine easily.
It's normal, every car does it.

 

[Orion]

Well the dealership insists that they didn't find anything wrong with it but
they flushed the system anyway, and tightened a few things, etc. I got it
back and the effect is reduced a lot. It's been taken down to somewhere
closer to a believable "normal power drain" versus the "suck you dry like a
goddamn vampire" level. They're playing stupid. I took Carl's advice and
insisted that I drive any other WRX of my choosing and they said no problem.
I said this before getting my car back. Now there's probably not much
difference so there's not much point. Perhaps I'll ask about the Forester
XT

Incidently, how many people have test-driven the STi? My dealership said
that Subaru gave them specific orders NOT to drive them (even the dealers).
They wanted the owners to be the one putting the miles on it. I asked if
this was because all of our STi's were sold before arriving and they said
no. But they were getting a black one with gold rims in that doesn't have a
name on it yet. We'll see.

 

[Tony Hwang]

Hi,
When a/c compressor is on, usually ECU increases rpm to compensate.
Also when you do hard acceleration, temporarily it cuts off compressor.
A/C system typically robs a few Hp. You can feel when a/c compressor
clutch kicks in on any car. Even with big V8s.
Tony

 

[Tony Hwang]

Hi,
Then maybe the ECU is not compesating the rpm when a/c kicks in.
In old carb. engines, solenoid did thejob. Now it is the job of
ECU. Either ECU does not know a/c is on(a/c on signal) or it is
not putting out signal to increase the rpm.
How about trying this;
With car parked and idling, turn on the a/c and watch the tach.
Is there any change in rpm? Usually V8 has bigger a/c compressor.
Tony

 

[D.K.]

Just a comment from a past Saab experience. I purchased the Saab 900S and at
the first warm weather I started using the air conditioner. I was amazed at
the loss of power and a learch / grone when the compressor cycled. A call to
the dealer "normal operation". Later that month I talked to a friend in the
auto air cond. business and he/we discovered a considerable OVER charge of
freon. That caused a very high head pressure during the on/off cycling.
After reducing the freon pressure to spec. the problem was almost going
except I still could feel the compressor cycle.

Yep, I've had exactly the same thing with my Impreza. A/c was installed
by dealer and it took 3 (!) trips back in order for them to diagnose the
problem and fix it. Only minor kick on/off ever since - even though this
is the first Impreza with only 90 hp and a really powerful a/c (cools much
faster and colder than the one we have in the Forester 2002).

DK