I am starting down the course of overhauling my a/c system. I am deciding what parts I should acquire. I have 126 technical manual cd, haynes heating and air techbook, and a venturi vacuum pump. I know I need a drier, manifold gauge, o-rings, 4 cans of r-12(I have my certification ), flushing solution(mineral oil), possibly a flush gun for my compressor and refrigerant oil. I have been tempted to just change the compressor while I am in there. The current compressor works but I have no idea how well and how old it is. Will any r4 harrison compressor from that era work. I see several on ebay marketed towards GM car owners. Are all r4 harrison compressors the same?

I have read several of the threads in this forum. The main question here is about the compressor.

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My Daily : 96 E-300 Diesel with 195,000 miles
Retired: 92 300D 2.5 T 345K miles and for sale
Retired: 95 E320 157K miles and currently parked with blown engine

Both retired cars are for sale as is my w124 shop inventory

You do not flush the compressor in the way you do the rest of the system...
You just empty it of oil and put new oil in and turn a few times by hand, empty and repeat a few more times... then seal it up until ready to install...
Use Brand New oil for the flush... something like Castrol Refrigeration Oil ...

That venturi vacuum pump.... is that one which uses a compressor to provide the vacuum ?
If yes, that is not sufficient to boil off the moisture from your system...

The proper kind can be rented from most rental places...you only need it a couple of days at most... if you have your ducks lined up at the start...

So you would suggest flushing the compressor with oil and not a new one then. Ok. I knew it was not traditionally flushable. Yeah I worded my first post poorly. Yikes. I have seen these posts knocking venturi pumps but I have seen no reason why they should not work if you give them enough pressure. Once you see the pressure reached on the guage for the correct altitude and outdoor temp then the system will be evacuated.

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My Daily : 96 E-300 Diesel with 195,000 miles
Retired: 92 300D 2.5 T 345K miles and for sale
Retired: 95 E320 157K miles and currently parked with blown engine

Both retired cars are for sale as is my w124 shop inventory

I am always surprised when people argue with me. Why ? Because I almost never say anything which is not standard industry wide information.. thus my answer can be easily checked either by Googling or a quick look at places like Aircondition.com.....
The venturi pump abilities are inherent in the physics of how it is made... don't trust me on this... check it out...

I can not say if all R4's are the same... so I did not say anything concerning used VS new... much has been posted in the archives on this stuff though..if you want to do a search.....

Fair enough but it just seems odd that these manufactures who manufacture industry standard equipment(robin air) would advertise venturi pumps and tech books would mention them. However if I put it on a guage and it draws enough vacuum then it will boil the water. Even if it is not an industry standard tool.

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My Daily : 96 E-300 Diesel with 195,000 miles
Retired: 92 300D 2.5 T 345K miles and for sale
Retired: 95 E320 157K miles and currently parked with blown engine

Both retired cars are for sale as is my w124 shop inventory

a venturi pump will get down to 28" or so but that's not enough. You need to bring the pressure inside down so that all the water boils at that ambient temp. When it boils, then the pump can remove it.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I thought the preffered flushing solution was Acetone......it will dry leaving no residue unlike mineral oil.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

"Fair enough but it just seems odd that these manufactures who manufacture industry standard equipment(robin air) would advertise venturi pumps "

Not odd at all... They are trying to sell you something... and I am not...

I don't think you want to use acetone in any of the rubber lines. A little oil residue is OK because the system has oil in it normally. But something with acetone-like viscosity would help in removing particles trapped in thicker oil inside the lines.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I think the preferred flush is sold in AC shops and is labeled " AC FLUSH"...
I don't know why people are always trying to find other stuff for this... sometimes other factors come into play....like safety of what you are breathing while doing it... flammibility... etc...

I needed to be clear on this becasue I should be attempting this in the next month. after if figure out what the problem is on my W123

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Seems like the research says that you need a great compressor to pull a good vacuum with a venturi. I probably could fake a good one in bursts with my compressor but it is not an industrial strength one. I'll call rental places or see if I can find a mechanical pump to borrow. Maybe I can get my money back at the harbor freight store(Man is that place cool).

__________________
My Daily : 96 E-300 Diesel with 195,000 miles
Retired: 92 300D 2.5 T 345K miles and for sale
Retired: 95 E320 157K miles and currently parked with blown engine

Both retired cars are for sale as is my w124 shop inventory

NOW you are talking... you will be pleased with that combination of actions...

I did find a rental place in town that has a unit. Now I just need to gather up my other ducks

__________________
My Daily : 96 E-300 Diesel with 195,000 miles
Retired: 92 300D 2.5 T 345K miles and for sale
Retired: 95 E320 157K miles and currently parked with blown engine

Both retired cars are for sale as is my w124 shop inventory

Be sure that among your ducks are goggles ( and I think a face shield at the same time are needed to protect you )...
We tend to consentrate on the symptoms and cures on the forum...and often forget to mention the safety related things....
Read all instructions on any cans and machines you use also....