C5 Covette AC questions

[weslp00]

Hi guys,

I'm a Newb on here but thought I'd ask around for some advice... Thanks in advance.
Just about to start an AC rebuild on my corvette. Control valve on the compressor was leaking so bit the bullet and got all new components incl the compressor which is an ACDelco item V7. I am going to flush all the tubes out but will replace the condenser and accumulator and orifice tube. There was virtually nothing on the screen of the OT (10 tiny sparkly bits )so not sure about an evaporator flush?

Question is the compressor. I need to balance the oil but I don't know what oil is in the new one and my system uses PAG150. Would it be better to dump the oil in the compressor and replace with the correct amount of PAG150 as it could be PAG 46 in there... also will the V7 be ok with PAG150 as I heard the V7 was designed to run on PAG46 ??

Please let know....

Stuart.

[bohica2xo]

Well, let's start with the procedure to add oil to a V7 compressor, along with all of the service information - just in case you have not read it, and for any others that might want do the same job:

http://www.omega-usa.com/client/images/ ... _ALERT.PDF

V5 / V7 compressors need to be oiled through the drain. If you are swapping oil types, or just don't trust what it may have come with - drain it, then fill it with the oil you intend to use. Spin it 20 turs or so, then drain the mixture out & replace it with fresh oil.

The best plan for a new compressor is to get all of the old oil out of the system. That way you can add back a correct charge. This can be difficult with parallel flow condensers, so replacement is a good call. It is at least 14 years old anyway.

Evaporators can be cleard of oil in place. Use the old accumulator as a catch can. Some stuff can still fly out of the accumulator so put a hose on the outlet to keep it off the bodywork. Hit the evaporator inlet with as much dry compressed air volume as you can. I usually spray as much brake cleaner in the inlet as i can, then blast it out in to the old accumulator. Then pull the old accumulator and blow some more. Walk away. An hour later blow in to the evaporator - can you smell any solvent? If so, blow some more & re-test in an hour.

[weslp00]

Thanks for the reply bohica2xo..this is really helpful!

Yes the condenser is actually 17 years old as its a 2001 car..I forgot to mention that Der!
By the way there has been a development with the new compressor..since I posted I opened it to look at the oil inside and guess what..there isn't any ! Its dry bar some assembly oil I assume. So much for "Compressor shipped with 2.5 ounces (74ml) PAG oil". That is disgusting sending out paperwork that is misleading to say the least! Imagine if I didn't oil balance it or change oil and fit it..BANG!
On the good side the casting is EXACTLY the same as the original..same stamp numbers etc...So silly question really but maybe it isn't a V7 (and what is the difference away )so can I just stick with straight PAG150 and dye? 2.5 came out my old one so 2.5 will go in the new.
On to the evaporator (that's the only bit with old oil in it now) Do I really really need to clear it? The oil in the system is like new and I found only a tiny piece (under a magnifying glass) of plastic in the suction side filter of the compressor which may have been form the accumulator. I do have loads of brake cleaner but only a regular compressor so I cant dry the air going in. Any alternatives if needs be ?
Also, if I do, how do I refill the evap. with the specified amount of oil on reassembly as the lines are horizontal to the bulkhead?

Stuart..

[bohica2xo]

I never trust a compressor to have what I want in it. I have seen them empty, full of 525 mineral oil when the tag said PAG, etc.

Some oil stays in each component. In accumulator systems there is some in the accumulator, that gets thrown away. The oil quantity issue is mitigated quite a bit in your case because the 2 other oil traps & the compressor is being replaced. Also on accumulator systems a slight oil overcharge is not as big of a problem. You can leave the evaporator alone if the OT was as clean as yours was.

Balancing the oil is not as important on a compressor with a sump like the V7. Fill the sump with the proper amount of oil, and put the rest of it in the accumulator INLET before you mount it. Accumulators have an oil metering system built in, and the oil will be fed to the compressor inlet in an orderly way.

PAG 150 & dye is a good plan. DEC PAG is the preferred stuff, but regular PAG is ok too as long as it is from a fresh container
https://www.autoacforum.com/messageview ... adid=17571

Just for fun, you can take a wheel type pipe cutter & remove the bottom couple of inches from the old accumulator & see what is in there.

Will you be charging from cans or a tank?

[weslp00]

Wow more great info...thanks!
Yes I now understand why I have heard that the accumulator is refilled with whatever is in the old one plus 2oz. Seems Like a lot but from there maybe it gets blown down the freshly cleaned suction side hoses and lubes the input to the compressor like you say. It is what it says..an accumulator or storage vessel for oil..makes sense that it can store up excess!
I made a real mess when I opened the system.. The compressor lines input lines were dripping with it. I am going to replace the low pressure and high side pipes/hoses in case of rubber deterioration.
Fancy a compressor being shipped dry and the paper work saying it had the recommended dose of oil. Like you say, you cant trust the sellers.
Heres a picture of the orifice tube... it has maybe 10 sparkles on it and it is alloy so must be compressor chaff.... but to clean out my evap. and possibly contaminate it with moisture from damp air/solvent on the strength of it seems overkill..does that look average to you? I know the next port of call after the OT is the evap. but how much muck could get in there.. I don't want to risk it as hopefully the majority of chaff will be in the condenser hence the nice replacement
I am gonna find a big can opener get that accumulator open..reminds me of the old days when we used to cut open engine oil filters on race cars to see whats what..usually ended up in tears..lol
As for refill time..I have a trusty mobile AC guy with all the kit so he can evac. and then weigh what goes in. I can also do a preliminary evac. with my mickey mouse gages and vac pump to check for leaks.

Stuart.

[bohica2xo]

That is very clean, and not unusual to see. Anything smaller than the screen is likely still in the accumulator. Your evaporator should be fine as-is.

I generally charge those systems with liquid through the high side before I start the engine. In to a vacuum you can get quite a bit of charge in before you begin to run it. Makes it go faster, and there is more refrigerant at start-up to begin returning oil to the compressor.

Pulling a rough vacuum on a system to check for leaks & remove trapped air is a good plan. remember that if it "loses" some vacuum on the first try that it is just outgassing the oil & dessicant. Pulling down to 20 inches & finding 10 inches the next day can be just fine. The second pull should hold.

[weslp00]

Thanks for the compliments about the OT..its only 17 years old !
By the way of this situation is my fault through lack of use. The car is a bit of a garage queen and even when driven I tend to leave the AC off and drive with windows open so maybe that caused the o rings on the control valve to harden and leak? Mind you I have read a lot about bad early Delphi V5 pumps.

And yes, I will bear the vacuum situation in mind.. the new oil and dessicant sacks are bound to soak up vacuum. I understand the liquid charge into the high side and kind of gives it a kick start.. not to be confused with liquid on the low suction side whichcould hydraulic the compressor. This is starting to take shape now thanks. I wish I had been and AC engineer instead of working for the phone company all these years!

GM specify 9oz of PAG150 oil total period in that particular system and 1.75 pounds of R134. I believe in a dynamic situation after start up will move the oil around but to start with after rebuild these are the capacities I am thinking of using..
Compressor 2.5oz
Accumulator 3.6oz (2oz+1.6oz that was in the old accumulator)
Condenser 1oz
Grand total of 7.1oz + dye to go into the respective components before evac. Now we have a shortfall of 1.9oz of oil so could this be hopefully still be in the evaporator or shall I add some more somewhere?

[bohica2xo]

It is unlikely that there is much oil in the evaporator. Think about the ounce of liquid in a shot glass, and what sort of mess it makes when you knock it over...

I would add 8+ of the 9 ounces back to the system. 2.5 in the compressor, an ounce in the condenser & the balance in the Accumulator. The bleed orifice in the bottom of the J tube will begin feeding an oil mist back to the compressor immediately.

[weslp00]

Me, I'd never drop a shot of spirits! Such a waste as its usually a double!
That new oil less compressor was a bit stiff and notchy when I turned it over last night..hope thats because its empty. I will fill it tonight.
Does it need priming on the bench seeing as it is empty and will it throw oil out of the rear.. also how about filling it first and then spinning/priming then empty and refilling as you explained yesterday ?
I hear you about the capacities and will follow along those lines plus dye..which has also got me thinking..I got my PAG150 from Supercool along with a 1/4 oz of dye..is that enough ? The stuff that came out looked like washing up liquid!

[weslp00]

Oh dear ..new condenser has just turned up and it looks like its put together by a chimpanzee. The zigzag cooling fins between the horizontal tubes are kind of sticking out a bit. That's Rock auto for you. Its an AcDelco part too ! I am trying to get a picture on here but it wont work for some reason..