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73z-6sp
05-25-2005, 02:19 PM
OK...I have a 73 Z28 which has vintage air a/c. We took it for a drive today and it started making a noise. At first I thought it was in the tranny. It sounds like something rattling, almost like a throw out bearing that is not aligned with the shaft if that makes any sense. This only occurs at 2k rpms and above. The a/c works great but the noise is driving me crazy. I am 99% sure it is the compressor (which is brand new Sanden from VA) since the noise disappears when the a/c is shut off and doesnt happen again unless you turn on the a/c. Has anyone else had this problem? Is it normal noise for these compressors? (I wouldn't think so but it is my first VA unit)

paul67
05-26-2005, 09:13 AM
check see if the clutch is loose

paul67

censo69
06-01-2005, 07:42 AM
Did you figure out the rattle yet? what type of mount is it? Has it always done it since you installed it? I work a lot on diagnossing compressor related problems on the OEM side hopefully I can help.

CarlC
06-01-2005, 08:57 AM
Had a similar problem on the wife's car. The pulley was cracked.

73z-6sp
06-01-2005, 11:23 AM
Did you figure out the rattle yet? what type of mount is it? Has it always done it since you installed it? I work a lot on diagnossing compressor related problems on the OEM side hopefully I can help.


No I havent though I have an appointment tomorrow to have someone check it out. I think it has done it ever since I installed it. I only have 350 miles on the car and even less on the A/C. Needless to say I havent used it much. The compressor is the Sanden mounted on a GM serpentine set-up using custom brackets. I have felt the compressor while it is making the noise and can feel no vibration that corresponds with the noise. Im hoping the shop can figure it out. Very annoying!

https://static1.pt-content.com/images/noimg.gif

paul67
06-01-2005, 11:41 AM
That pulley is realy close to those mounting bolts. I had that with an idle mount there was a close gap until the engine started then the tension on the belt pulled it to the bolt but you only saw it when it ran.
paul67

73z-6sp
06-01-2005, 11:46 AM
That pulley is realy close to those mounting bolts. I had that with an idle mount there was a close gap until the engine started then the tension on the belt pulled it to the bolt but you only saw it when it ran.
paul67
I agree, it is close and that was the first thing I looked at once I heard the noise. The belt never comes in contact with any bolt or mount.

Is it possible the system is under/over charged and causing the noise? I noticed today that the compressor cycles quite a bit even with the temp turned to the coldest setting.

paul67
06-01-2005, 11:55 AM
Very carefully spray some wd40 or like at were the bearing is when the comp is running and see if it gets quieter not much if it does its poss the bearing giving up under load. Do you mean coming on and off , do you have a low pressure sensor on the a/c also check alt bearings, does it do it if you put a load on the alt like lights heater etc or just a/c.
paul67

73z-6sp
06-01-2005, 12:01 PM
OK, I will check that. I have to go to work so it will be tomorrow morning.

I mean that the compressor comes on and goes off. I have the switch in the dryer that came from VA that is suppose to switch it off if it is over/under pressure.

It only makes the noise if the A/C is on. I can run everything else on the car electrically and it will not do it. Turn on the A/C and it immediately starts. (Above 2k rpm)

Thanks for all your ideas and advice. I appreciate it.

Aaron

73z-6sp
06-02-2005, 08:26 AM
I need to rant! I took the car in this morning and the people there were so unresponsive and unwilling to help that I left with my car! So I didnt find out anything. They wouldnt even send a tech out to talk with me about the problem. They just want me to hand over my 7+ year, $20k project and oh yea! sign a waiver so we cannot be held resposible if we damage your car! And to top it off, first thing out of the guys mouth is "How can you hear anything over that loud exhaust?" He asked that three times! This is suppose to be the best place in town. I dont even want to go to the worst!
Maybe I am expecting too much but I just could not leave my car there. I had a bad feeling about it. Now I'm confused on what to do. Maybe I will just live with the noise!

censo69
06-02-2005, 11:26 AM
You say the noise starts as you approach 2000 RPM. Does it go away at higher RPM's say 3000? If it does it sounds like a resonance problem try and find someone with the exact same set up or close to as possible. It is very possible the natural frequency of the spinning compressor is excited around 2000 engine rpms. This in and of itself is not usually a problem, however when the natural frequency of the bracket and engine all align look out because it will make some noise. Would it be possible for you to record the noise with a digital camera once with the compressor on and once with the compressor off for an A to B comparison. I will try to get some people at work to take a listen. Also you stated the when you touched the compressor you could not feel the vibration of the noise did I read that correct? If so try holding the discharge and suction lines and follow them around the entire system. While doing this look for any areas where a/c components touch other components like lose attachment of condenser to rad support. Or even the evaporator vibrating inside the case. Rule of thumb should be pretty obvious (no metal to metal contact). Someone else brought up the possibility of an overcharge. Overcharging the system could cause some vibrations as well. And finally out of curiosity does the system perform well as far as outputting cold Air? Good Luck

KUL FIR CHICK N
06-03-2005, 04:10 AM
I'd put my money on an overcharge. You say you have rapid cycling even on max cold. You are probably kicking it off by the high pressure safety switch. You need to get some gauges on it. Your system should be charged by weight to 1.8lb. This should be done with a good charging station. A bathroom scale is nowhere near accurate enough. The high pressure will cause the rattling noise you speak of and will very quickly destroy your compressor, then the rest of your system.

Ryan