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  #1  
Old 08-27-2005, 04:24 PM
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A/C rebuild something went wrong.

I just finished charging my A/C and fired it up. The compressor is making a strange noise. About once every second or two it makes a noise similar to lightly tapping a tin can with a screwdriver.
For the most part I followed the resently posted pictorial. I did all of the to-doís like changing all of the seals, valve, dryer, and flushed the system. For the lube I used synthetic ester oil and charged it with what I estimate to be around 2.9lbs of R12.

The gauges are normal and the A/C works just fine.

Possible problem: I originally put the 4oz. of oil in the compressor and then 4oz, in the dryer like in the picture, but when your trying to connect the lines most of the oil pours out. I knew I lost most of the oil, so I filled the dryer with about 6 1/2ox of oil.
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1984 300D / The only Benz I have

Completed weekend projects
  1. R/R front crankshaft seal
  2. R/R nearly the whole vacuum system
  3. Converted to WVO www.greasemachine.com
  4. Upgraded to electric power locks
  5. Upgraded and rewired stereo/amp/speakers
  6. Installed 2.88 differential
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  #2  
Old 08-27-2005, 05:24 PM
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At this point in time.... if it is working ok .... you may need to just run it long enough to get the oil spread around to where it will naturally pool...
What are your guage readings at 15 minutes after running approx 1500 rpms?
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  #3  
Old 08-27-2005, 05:52 PM
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My compressor has been making that "tin can" noise for years. It started not long after I converted to R-134a. I'm just going to run it until it dies, then convert back to R-12.
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  #4  
Old 08-27-2005, 06:01 PM
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I just hate the thought of having to redo what has now cost me $350.oo. I would feel better with some information about why it is doing this and/or what can be done to fix it.
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1984 300D / The only Benz I have

Completed weekend projects
  1. R/R front crankshaft seal
  2. R/R nearly the whole vacuum system
  3. Converted to WVO www.greasemachine.com
  4. Upgraded to electric power locks
  5. Upgraded and rewired stereo/amp/speakers
  6. Installed 2.88 differential
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  #5  
Old 08-27-2005, 07:48 PM
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"what I estimate to be around 2.9lbs of R12."

I hate the idea that all the preaching I have done over the last couple of years concerning the need to accurately determine that amount of refrigerant installed was for naught.

I hate that after asking you about the guage readings under specific circumstances... which are required by the FSM for starting the diagnosing sequences... that you did not provide them... and that you did not follow procedure sufficient to ensure the CORRECT amount of oil in your system.... I have preached about that for a long time also... because the books talk about how important it is....

"I just hate the thought of having to redo what has now cost me $350.oo. I would feel better with some information about why it is doing this and/or what can be done to fix it."

We are not magicians... and we can't tell except from your descriptions what may have happened....and something which you were not aware of may have happened which naturally you can not tell us about since you were not aware that it was of consequence...

So you need to go run the AC to see if getting the unknown amount of oil you do have in it spread around will fix the noise problem... and stabilize the system like the FSM requires in its test procedure.....and then report back the guage readings....and the ambient temperature and vent temperatures at low blower speed also....
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  #6  
Old 08-27-2005, 09:53 PM
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I have the reading it was a nerve racking 15 min but here they are...
Still making noise

Low side 33psi
High side 250psi
Outside temp 93 degrees
Blower temp on high 50 degrees

It also seems to be taking more engine power at low RPMs than my old compressor. Maybe it is just my imagination.
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1984 300D / The only Benz I have

Completed weekend projects
  1. R/R front crankshaft seal
  2. R/R nearly the whole vacuum system
  3. Converted to WVO www.greasemachine.com
  4. Upgraded to electric power locks
  5. Upgraded and rewired stereo/amp/speakers
  6. Installed 2.88 differential
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  #7  
Old 08-27-2005, 10:04 PM
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So the noise remained exactly the same over that time period ?
And you are absolutely sure the noise is coming from the compressor ?
Did you put your hand on it or a stethescope to it ?

What were the symptoms which caused you to replace the compressor ?
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  #8  
Old 08-27-2005, 10:08 PM
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I distinctly asked for vent temperature with blower on Low...
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  #9  
Old 08-27-2005, 10:27 PM
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The compressor made the noise all through out the process.
There is no sound when the compressor isnít on.
Sorry, about the blower temp I was in such fear of destroying this compressor that I am sure I went cross eyed when you asked for me to run it for 15min.
The clutch going out what caused me to rebuild the system
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1984 300D / The only Benz I have

Completed weekend projects
  1. R/R front crankshaft seal
  2. R/R nearly the whole vacuum system
  3. Converted to WVO www.greasemachine.com
  4. Upgraded to electric power locks
  5. Upgraded and rewired stereo/amp/speakers
  6. Installed 2.88 differential
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  #10  
Old 08-28-2005, 02:00 AM
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I have spent the past hour or so looking through old posts. One of the causes for this noise seems to be a loose belt. Even though I knew I had everything tight I just went outside to double check. MY BELT IS LOOSE! I am too tired to fix it now but this gives me hope. Keep your fingers crossed for me.

Should I add an ounce or two of oil?
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1984 300D / The only Benz I have

Completed weekend projects
  1. R/R front crankshaft seal
  2. R/R nearly the whole vacuum system
  3. Converted to WVO www.greasemachine.com
  4. Upgraded to electric power locks
  5. Upgraded and rewired stereo/amp/speakers
  6. Installed 2.88 differential
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  #11  
Old 08-28-2005, 06:16 AM
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Location: central Texas
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Ok, if it was only the clutch going out then we can assume that major trash was not in the system... since you said you flushed .... I was only worried that the ' manifold' as they call it... the actual pipes at the compressor... the tubing attached to the rubber lines had not hidden trash.... the FSM calls for Replacing it in that case because some have a screen inside them which make proper flushing impossible....
If this is just a belt that will be great...
However, there really is no way to tell if you need more oil or not... only complete evacuation and flushing , then careful measuring putting it back in can provide the ability to know how much is there.
Remember that too much oil is a real problem also.... I would worry myself about placing all the oil into the R/Dryer .... I think usual procedure is to spread it around some...
When you evacuated ... did you do it on both the service ports ? IE, both sides of this oil load ?
Your pressures seem high but I would not change anything until you have a couple of hours of running to see if it is the slug of oil needing to get distributed...
Be sure the fins on the condensor and radiator are clean and not bent. And that the aux fan will kick in when needed.
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  #12  
Old 08-28-2005, 09:48 AM
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Location: Cape Cod
Posts: 59
When converting these cars to R-134, my only problem has been the v-belt.
This problem was solved when i went to use the OEM belt manufactured by Contitech. Problem solved.
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  #13  
Old 08-28-2005, 02:03 PM
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Who would think such a god awful sound could be made from a loose belt. I just tightened it and everything seems fine.

I am off for my first cruse with A/C in over 3 weeks
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1984 300D / The only Benz I have

Completed weekend projects
  1. R/R front crankshaft seal
  2. R/R nearly the whole vacuum system
  3. Converted to WVO www.greasemachine.com
  4. Upgraded to electric power locks
  5. Upgraded and rewired stereo/amp/speakers
  6. Installed 2.88 differential
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  #14  
Old 08-28-2005, 02:20 PM
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Location: central Texas
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"And you are absolutely sure the noise is coming from the compressor ?"--Me in post #7

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  #15  
Old 08-28-2005, 02:39 PM
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Well either the clutch or the compressor. I say this because the noise is not there with the A/C turned off.

I haven't been able take that trip yet
I want to replace the service port caps first and I left my lights on my other car... Waiting for the battery charger to do its job.

Sorry, I didnít reply to the bulk of your questions. I appreciate your thoroughness reading through the post you obviously are an authority on the subject. I will take new readings and answerer your questions once I get back from NAPA.
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1984 300D / The only Benz I have

Completed weekend projects
  1. R/R front crankshaft seal
  2. R/R nearly the whole vacuum system
  3. Converted to WVO www.greasemachine.com
  4. Upgraded to electric power locks
  5. Upgraded and rewired stereo/amp/speakers
  6. Installed 2.88 differential

Last edited by brabus; 08-28-2005 at 02:51 PM.
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