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  #1  
Old 06-21-2001, 08:50 AM
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Sorry for the all-too-simple questions, but I just wanted to get it right.

I just replaced my old silver-colored York compressor with a new black York compressor about a month ago.

My questions are:
1. I was told all new York compressors now come in black. True?

2. Is the receiver and dryer referring to the same thing? If so, should I also replace it?

3. Does my car have an expansion valve? If so, should I also replace it?

Hope that you guys will help me out, thanks in advance!

Mervyn
1983 W126 (280SEL)
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  #2  
Old 06-21-2001, 08:52 AM
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One more thing.......

One more thing to add:

I noticed my mechanic did not cover the ends of the hoses while replacing the compressor. I've read in the threads here that we ought to keep the system clean. So would it be too late to replace the dryer now?

Mervyn
1983 W126 (280SEL)
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  #3  
Old 06-21-2001, 09:01 AM
LarryBible
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Has the system already been evacuated and charged?

If not, you should most definitely replace the filter/drier.

If the lines were left open long enough to replace the compressor, it's not a big deal as long as you evacuate the system properly.

You did not indicate whether or not you are converting to r134 at this time. If you are, there are other steps that it would be good to take at this time.

There is really no need to replace the H-Block (expansion valve) unless it is leaking or you are changing to r134. Actually I changed to an r134 Hblock when changing over my 240D. The new H-Block subsequently leaked and I replaced it with a new R12 H-Block that I had on hand. I could not tell the difference in the cooling effect when changing the H-Block.

Summary; if there are no leaks and you are staying with R12 and have yet to evacuate the system, I suggest you replace the filter/drier, pump down, ensure that it will hold the vacuum for several minutes(gross leak check) then charge the system.

Good luck,
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Old 06-21-2001, 09:08 AM
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I don't know whether all new Yorks are black but they have been available that way for years. They were sort of like a generic out the back door project for years. It may be the only way to get them anymore. I wouldn't worry about it.

The reciever-drier is a reservoir/filter/descicant device that should be replaced every time the system is openned according to MB. In humid climates such as Florida it is specially important.

To replace it one must evacuate the system, replace the part, and reevacuate and charge the system.
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Continental Imports
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  #5  
Old 06-21-2001, 09:14 AM
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Dear Larry,

Thanks for your very prompt reply.

Apologies for leaving out certain crucial info, here they are:

1. No conversion at all. Was using R12 previously, and still is using R12 now.

2. As far as I see it, there's no leak whatsoever anywhere in the a/c system.

3. Sorry but what is meant by "evacuating and charging" the system? If charging refers to topping up with R12 gas, then I had that done.

4. The hoses were left open for about 45mins while the compressor and clutch were being replaced.

With these additional info, would your advice still be the same?
-------------------------------------------------------
Summary; if there are no leaks and you are staying with R12 and have yet to evacuate the system, I suggest you replace the filter/drier, pump down, ensure that it will hold the vacuum for several minutes(gross leak check) then charge the system.
--------------------------------------------------------

Thanks again Larry!

Mervyn
1983 W126 (280SEL)
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  #6  
Old 06-21-2001, 09:20 AM
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Dear Steve and Larry,

Holy cow, I'm located in Singapore where it is really hot and humid!

Ok, I am already thinking of replacing my receiver/dryer tomorrow, but can you explain to me what is meant by the following?

1. "Evacuating the system"

2. ".......pump down, ensure that it will hold the vacuum for several minutes(gross leak check)....."

Best regards,

Mervyn
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  #7  
Old 06-21-2001, 09:35 AM
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In the first instance evacuating refers to the removal of the refrigerant so that the system can be disassembled.

In the final act the system must be placed in a vacuum strong enough to lower the boiling point of water to below ambient temperature. The point being, that just sucking on a bottle of water won't remove the water, but reducing the boiling point till the water boils and then sucking out the vapor will get rid of the water. The level of vacuum necessary is defined by the temp of the day/refrigerant. The level of vacuum is probably only achieved in 10% of all evacuations as it requires vacuum pump oil to be changed after only a few events (something universally not done). The level of vacuum necessary can not be read with a standard gauge; a micron gauge is necessary.

Using the vacuum for leak checking is a good basic test but really isn't very accurate as there are great differences between the way varies components leak under pressure or vacuum. Vacuum can cause a leaking shaft seal to not leak (for instance).
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  #8  
Old 06-21-2001, 09:44 AM
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Dear Steve,

Many thanks for taking the trouble to explain. I appreciate that!

Ok, I can now say safely that I'd evacuation done before removing the old compressor, and it was charged with R12 after assembly. I've been driving the car for about 1 month ever since.

I was at the workshop all the while during the repair, and at no point in time did I see my mech carrying out the "vacumm leak test" as mentioned by Steve and Larry. Perhaps they are not even competent with this particular procedure!

Will it be alright to go without the "vacumm leak test"?

Mervyn
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  #9  
Old 06-21-2001, 12:13 PM
LarryBible
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If it is holding a charge the leak test is unnecessary, however, as Steve said the filter/drier should be changed and the system evacuated with a strong vacuum for a period of time. If the technician at no time used a vacuum pump, the system is marginal at best.

If the equipment is available to him, it would be best to remove charge into a machine so that the R12 is not lost, replace filter/drier, draw a vacuum with a wet vane vacuum pump for a period of time, recharge with R12.

The gross leak test I described was merely a "poor boys" test of the system to see if there is a large leak in the system before wasting refrigerant into a system that has a large leak.

Good luck,
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  #10  
Old 06-22-2001, 08:59 AM
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Got it done! Thanks.

Dear Steve and Larry,

Got the receiver/dryer (brand: "Hansa", price: USD$14) replaced today, together with the 2 pressure switches (high pressure switch and low pressure switch). Vacumm pump was indeed used in the procedure before charging with R12. My mech did not have a machine to store the R12, so he leaked it into the atmosphere, and so had to charge new gas into the system. (a waste of money though)

One interesting point is that it cost me only USD$11 to charge up fully with R12. My understanding is that it cost much more in the US, which is one reason why many people are converting to R134. R12 is readily available here, and is rather cheap. I was charged slightly more today for the R12, usually I pay about USD$8.

Thanks to you guys for the invaluable help. I could not have learnt more without your advice. Cheers!


Mervyn
1983 W126 (280SEL)

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