Noisy Air Con

2571 Views 26 Replies 10 Participants Last post by PMI, Jul 16, 2005

rriggs

Discussion Starter · Jan 8, 2004

My air con is very noisy. Is this normal for a '97 NG900? You don't notice it at speed but in traffic or stationary it rattles away quite loudly. Seems to work OK...

Cheers

Rog

1 - 20 of 27 Posts

n1np

· #2 · Jan 8, 2004

I have the same problem with my 1997 900set. It sounds like a low groan when the ac kicks on and the whole car shudders. The ac blows ice cold, though. Just had the belt replaced and no change. I would like to hear other experiences as well.

Ben, N1NP

rriggs

Discussion Starter · #3 · Jan 8, 2004

That's the one! At least it's not just me. Question for both of us now is whether that's normal for '97 cars or whether the compressor is on it's way out...

Rog

ragtopcav

· #4 · Jan 8, 2004

I believe there is an electromagnetic clutch which is part of the aircon on/off, I wonder if that is the culprit?

toenail

· #5 · Jan 9, 2004

My new to me '97 900 SET showed the same symptoms. Indy mech knew what it was right away. AC system is super sensitive to over/under charging. He evacuated sytem and measured contents, then subtracted overage and re-filled. Problem solved. Hope this works for you.

In the interim, activate the ECON buttom on your ACC system when running heater and it will prevent the AC from kicking on.

maallen40

· #6 · Jan 9, 2004

Mine has started groaning lately. It works fine but I don't have a clue what this means.....anyone have the same groaning problem?

rriggs

Discussion Starter · #7 · Jan 9, 2004

toenail said:
My new to me '97 900 SET showed the same symptoms. Indy mech knew what it was right away. AC system is super sensitive to over/under charging. He evacuated sytem and measured contents, then subtracted overage and re-filled. Problem solved.

I wonder if this tallies up with my other active thread about a pink stain on my carpet. If my air con is leaking pink stuff into the cabin this would mean my AC system is under-charged and is therefore causing the noise from the compressor?

Rog

toenail

· #8 · Jan 10, 2004

It's been a while since I used the AC but my recollection is that it made a heck of a racket and caused the car to shudder considerably. A moaning/groaning accompanied by heavy vibration is a pretty accurate description.

Not sure about pink stains and/or their origin and what that might indicate. Don't know the color of liquid refrigerant.

rriggs

Discussion Starter · #9 · Jan 13, 2004

Been suggested by a (non-Saab) mechanic that the noise from the air con sounds liuke a sticking expansion valve. Means nothing to me, can anyone elaborate/deny?

Rog

Munki

· #10 · Jan 13, 2004

toenail said:
It's been a while since I used the AC...

Not using the A/C for prolonged periods can cause the internal seals to dry out leading to leaks and expensive repair bills. Aim to use it for at least once a week to keep it in good shape.

The Swedish Bullet

· #11 · Jan 13, 2004

rriggs said:
toenail said:

My new to me '97 900 SET showed the same symptoms. Indy mech knew what it was right away. AC system is super sensitive to over/under charging. He evacuated sytem and measured contents, then subtracted overage and re-filled. Problem solved.

Click to expand...

I wonder if this tallies up with my other active thread about a pink stain on my carpet. If my air con is leaking pink stuff into the cabin this would mean my AC system is under-charged and is therefore causing the noise from the compressor?

Rog

Rog, I think we've connected the dots. I have the mystery stain, the mystery smell, AND the mystery groan noise as well. (Although the groan seems to quite often be precipiated by shifting gears...but not always...)
Carl.

toenail

· #12 · Jan 14, 2004

(Although the groan seems to quite often be precipiated by shifting gears...but not always...)

That sounds an awful lot like hooter valve (bpv) failure. On mine most times I pass from vacuum to boost the bpv would make a weird moan (not a hoot as described by others). I just repalced it with a Forge. Problem solved.

Been suggested by a (non-Saab) mechanic that the noise from the air con sounds liuke a sticking expansion valve. Means nothing to me, can anyone elaborate/deny?

My indy mech did make mention of this valve when talking about issues with my system. He alluded to the fact that it was a common failure.

n1np

· #13 · Apr 19, 2004

UPDATE:

The local SAAB dealer recently checked my AC system and said with a straight face "You need a new compressor: $1350 parts and labor" :nono; . Not long after this, the AC stopped making noise. Actually it stopped doing anything at all

(it was noisy but ice cold before this). Now with the AC on, no air comes out of the vents. In ECON mode, the fan works fine.

Has anyone else satisfactorily resolved their AC problem? The charge level in my system is supposedly correct. Can the AC clutch be replaced by itself (The dealer did not seem to be willing to explore this option)? If so, what is a reasonable repair cost?

Side note:
I used to like working on cars. I no longer enjoy fixing cars. I want to pay someone else to do it for me while I do something more interesting. I fix machines every day at work, perhaps that is why I feel this way about cars.

Ben N1NP

Bangkokburt

· #14 · Apr 26, 2004

uh oh my air con died last week, was driving along and "gas" / water vapour (not sure it looked like mist) started venting into the cabin.

The fans work fine but it sure aint cold.

Its the hottest it has been for the last two years (in Bangkok) over 40C out there, just sent it in to get fixed - am scared of the likely costs involved if I need a compressor.

Especially scared as every other person I know has had to replace their compressor, and I have heard they are expensive. Will share more tomorrow when the shop calls back...

bkrell

· #15 · Apr 26, 2004

A shudder could be caused by a faulty idle control valve. If it's stuck, your revs can drop under the extra load of the a/c. As for over pressurizing, I did it to my Saab and my Honda yesterday! The saab seemed to handle it better than the honda. The Honda would cut the compressor intermittantly, I guess to avoid anything dangerous???

As for a faulty clutch, it often takes the compressor with it. The clutch is what is used to cycle the compressor on and off. If it gets stuck in the "on" position, it will burn up the compressor eventually.

Happened on my old BMW.

n1np

· #16 · Jul 5, 2005

**UPDATE** (a year or so later . . .)
I took my car in to the local dealer this morning. The plan was to have the AC compressor replaced (see above posts). The technician diagnosed the problem as a faulty "low-pressure valve", replaced that and recharged the system. They did NOT replace the compressor. I took the car out and drove around only to find that it still made the same noises as before. I took the car back and let the service manager listen. His diagnosis: dry bearings in one of the belt pulleys

. I am heading out to the garage to attempt to lubricate the pulley bearings and will post the outcome later today.

Ben N1NP

PMI

· #17 · Jul 5, 2005

Has anyone used SI 854-2143 "A/C System Noises" with any success? (text is posted somewhere on the SN board, search by SI number) Or the Air Conditioning Diagnostic Charts on saabsite?

I would think that pulley noise would be present with the AC off, in other words all the time. AC clutch, compressor, etc. noise only when the AC is running.

n1np

· #18 · Jul 5, 2005

PMI said:
I would think that pulley noise would be present with the AC off, in other words all the time. AC clutch, compressor, etc. noise only when the AC is running.

The dealer's answer to that question this morning was: you can't hear the pulley noise in the cabin with the AC off, but can hear it in the engine compartment with the AC off. He theorised that the extra load of the compressor caused a greater stress on the pulleys, and therefore a louder noise.

I have removed the belt and upper and lower idler pulleys, and am partially following the dealer's advice. Dealer's advice: soak down the pulleys with WD-40. I have pooled some synthetic motor oil on top of the bearing seals and spun the bearings by hand in hopes that some of the oil would make it past the seals. It didn't take long for the bearings to turn more freely, but also with little rough spots. They are still soaking.

So I need new pulleys, and a new belt (looks a lot worse when it is off). My question now is: do I need to replace the belt tensioner as the dealer says is "standard practice"? The car has 62,000 miles and I don't see anything obviously wrong with the tensioner.

Your opinions are appreciated.

Ben N1NP

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PMI

· #19 · Jul 5, 2005

The dealer is part right, but that can almost be worse than completely wrong.

The dealer's answer to that question this morning was: you can't hear the pulley noise in the cabin with the AC off, but can hear it in the engine compartment with the AC off.

Yes, but if you take the belt off, you can easily detect a dry pulley bearing, The pulley will spin like a top, and have some play in the axis. A properly lubricated pulley will spin a few revs then the grease will slow and stop it. Dry pulley will have clicking metalic sound when held to your ear and spun. A good pulley will have no sound. In any case, they often fail before 60k, so replacing them is a good idea.

He theorised that the extra load of the compressor caused a greater stress on the pulleys, and therefore a louder noise.

No. Load may strain the belt, but only more tension and higher rotation speed will stress the idler pulleys.

soak down the pulleys with WD-40

if it works at all, this would be a very temporary solution. WD-40 is part solvent. It will dissolve and wash away bearing grease. Thin oil will not help. The idler pulleys fail because even the thick grease escapes past the seals over time. You would have to remove a seal, and repack the bearing. Not so easy on these.

So I need new pulleys, and a new belt (looks a lot worse when it is off).

Yes, at 60+ k miles the idlers are on borrowed time. You can convert to the single idler configuration with a short belt, and save the cost of one pulley. To find out more about that, search for "short belt" on this board.

do I need to replace the belt tensioner as the dealer says is "standard practice"?

Not on the NG900, 1994-98 with the large metal tensioner pulley, unless something is obviously wrong. The dealer probably services more 9-3 models by now. On the 9-3, I am not sure, the tensioner is different. The larger pulley on the NG900 tensioner rotates slower, so the bearing lasts longer. I replaced mine at 100k, along with the alternator, and I am pretty sure it was still ok.

Good luck, and here is a link to some information I collected on the NG900 pulleys:

http://www.geocities.com/ng900set/Serp_Belt/idler_pulleys.html

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n1np

· #20 · Jul 5, 2005

PMI:
Thanks for the advice.

I put the car back together and can no longer hear the noise in the cabin, but can still hear it (when the compressor kicks on) in the engine compartment. This tells me that whatever oil got into the bearings had some effect, unless simply taking the belt off and putting it back on did something (doubtful).

The pulleys do not spin completely free, they go a couple of revs then stop. I feel comfortable in driving the car until the new pulleys and belt arrive.

Ben N1NP

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