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Total System Replacement - Apportion out oil to components?

FOMOCO on Wed March 20, 2013 12:50 AM User is offline

Year: 1994
Make: Ford
Model: Bronco
Engine Size: 5.8L
Refrigerant Type: HFC-134a
Country of Origin: United States

Compressor seized a few winters ago, finally getting around to fixing it. Total system replacement. Replacing EVERY component: Compressor, Condensor, Evap, Orifice tube, Accumulator, all hoses, Cycling pressure switch and HPCO. Everything refr. touches will be new.

System Capacities: 134a - 33 Oz., PAG 46 - 7 Oz.

Got a new Denso FS-10 compressor, shipped sealed with the total sytem charge of 7 Oz. of PAG 46.

The usual component replacement rule is to apportion out oil to the replaced component, such that the total system oil capacity will still be met. The Denso instructions follow that, they have you drain out of the old compressor to check amount that was retained, and go from there.

But what about a totally NEW system?

Approach #1: The Denso comp. has the system total oil charge of 7 Oz. in it. After installation, I could hand-turn the comp. shaft 10 turns or so to clear the compressor, and not apportion any oil to the other new components. Will oil migrate all the way around the system soon enough after startup to avoid starving the compressor of oil?

Approach #2: Deduct some of the 7 Oz. of oil from the compressor, and apportion a couple Oz. to the accumulator, maybe 1 Oz. to the Evap, another 1 Oz. to the condensor. I can't spread too much around, as I would think the compressor should retain at least a few Oz. and with a system charge of only 7 Oz. total, there isn't much to go around.

I wonder what they do at the auto assembly plants. Would they really be putting small amounts of oil in all the major components? Seems like that would take too much time=$$

Edited: Wed March 20, 2013 at 12:52 AM by FOMOCO

AutoCool on Wed March 20, 2013 4:51 AM User is offline

Think of this as a new engine, what would you do then? Rotating components have to be prelubed because it takes a little time before oil gets pumped around to all the bearings and such.. Your new AC compressor is the only rotating component, and that's already lubed. Think of your new accumulator/filter drier as your new oil filter. You want the oil filter saturated with oil, so upon initial startup you don't waste time soaking the filter with oil.

The most important thing to avoid is slugging the compressor intake with oil. Pouring off a couple of ounces of oil into the accumulator inlet before assembly will help prevent oil starvation.

When I've had nitrogen available, I usually use that to prelube the system, charge nitrogen through the high side and release through the low side until I just begin to see signs of oil on the low side. Then vacuum before charging.

Long ago, mechanics didn't care about refrigerant recovery or even using a vacuum pump during installation. It was common practice to just use the compressor as a vacuum pump, and charge freon through the intake while blowing out the trapped air through the discharge. Modern compressors generally don't have a sump like the old york/tecumseh "lawnmower engine" compressors do. They rely on sort of an oil misting for lubrication instead.

Not really sure how it's done at assembly plants, I would assume that compressors are installed "dry" if for no other reason they don't want to risk oil spills under vehicle assembly. Too messy.

NickD on Wed March 20, 2013 6:40 AM User is offline

Prefer using an oil injector like this one, injecting into a well vacuum system.

Pouring PAG oil into a moisture prone system, a little here and a little there is tantamount to suicide.

Each to his own on the subject.

GM Tech on Wed March 20, 2013 8:46 AM User is offline

The entire system oil charge is inside the compressor when the compressor is mounted to the engine at the assembly plants. Been done that way ever since compressor manufactureres argued about dry starts and compressor failures when assembly plants failed to add oil-- so the plants made the compressor folks responsible and if ever another dry start- it would be the fault of the compressor people.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

HECAT on Wed March 20, 2013 10:35 AM User is offline

Approach #1 works and this is how it is done at the factory. I just don't like the idea of the new lube for your new system being the shipping oil that came in the compressor. The factory is getting fresh stuff that is being installed within a reasonable amount of time. From the aftermarket we do not know if it truly contains the correct amount for your system, or how long it has been warehoused (on the "shelf"). Since the PAG is also very hydroscopic, I would drain out the shipping oil and install fresh oil in the compressor or distributed in the components as you like.


HECAT: You support the Forum when you consider for your a/c parts.


FOMOCO on Thu March 21, 2013 12:28 AM User is offline

GM Tech & HECAT - thanks for the assembly plant info. I decided to go that way too.

Originally, before the compressor arrived, my plan was to dump the oil out of the new compressor and use new oil right out of the bottle. But after reading the Denso info that came with it that said it had the full 7 oz. system charge, i was thinking of not changing it out.

But HECAT's comment on age and quantity unknown fit right in with a nagging feeling that I really didn't know. I looked for a mfg. date code on the compressor, I suspect it was on a sticker on the front face of the clutch, most of the sticker's print wore off against the paper cushioning in shipment, not readable.

So I took off the shipping plate, it went pfffft, probably charged with Nitrogen. I dumped and cranked out a little over 6 oz. out of it. I put in 7 oz. of fresh PAG 46 and replaced the input and output port O-rings.

With all new parts, and new pump oil in my little Robinair 1.2 CFM vac pump, I was surprised how quick it was pumping down. I stopped after 5-7 mins. to do a quick check if vac would hold, looked great. Ran it then for almost an hour. Rock solid vacuum. It's all charged up and working fine now. Tomorrow I'll put all of the engine air intake plumbing back on.

I was surprised how much fiddling I had to do with parts to make them fit:

The cycling pressure switch that screws onto the side of the accumulator wanted to bunch-up the O-ring, instead of going over it. I thought the O-ring may have been a little too loose, so swapped it out for another one. Same thing happened. On closer look, there was a design problem. The old switch had a slight chamfer on its inner diameter, so the switch would compress the O-ring inwards as it screwed on over it. The new switch had no chamfer, was a sharp 90 degree edge. It had a molded-in ridge on its face instead, that was supposed to "sweep" the O-ring in... that didn't work. So I carefully sanded a chamfer into it, being careful not to get grit inside. Then it worked fine.

The aluminum liquid line from condensor to evap orifice tube spring-lock I had to bend this way and that. The replacement line was a rough, very rough, approximation of the original line. I wanted to be sure that there were no forces pulling or bending the spring-lock connection in particular.

The hose from compressor to input of the condensor wouldn't fit, the hose would hit the engine airbox big bracket and not go straight into the condensor fitting, so had to bend (urk!) the condensor input line a bit to get clearance.

I have had difficulties in the past with Accumulator to Evaporator matchups on Ford fixed-orifice systems where the evap was under the hood. So this time I made sure the same company made both of them... well, it didn't matter. The Accumulator has two bracket ears welded tangentially on its sides 90 degrees apart - those fit the evap case ok, but either the accumulator input pipe is a bit too short, or the evap outlet pipe is too short, as when I mated them up, I couldn't get the top ring bracket to work out. The original top ring bracket fits over the top seam of the evap case, and is fastened by the two screws that hold the top of the case together. Then it extends forward as an arm, and becomes a band that should encircle the upper end of the accumulator, using a screw to tighten the band.

Now the arm is too long to fit. I'll have to see if I can drill new mounting holes in the ring bracket to move it rearwards, but not sure the new angles will work out. If this was being done at the corner garage, they'd probably just throw the bracket in the dumpster, and no one would be the wiser.

The accumulator was made in China, don't know about the evap, it could have been too. With American brand names on parts, it's getting hard to know in advance where a part is actually made.

TRB on Thu March 21, 2013 11:27 AM User is offlineView users profile

In the auto a/c business, 90 percent is made in china these days. If not directly indirectly.


When considering your next auto A/C purchase, please consider the site that supports you:

FOMOCO on Fri March 22, 2013 12:46 AM User is offline

This project just did not want to go easy...

With some hammering, drilling, and careful bending, I was able to get the original top ring bracket to fit and help hold the accumulator.

Then it was on to fix a (too) short circuit. The new manifold and hose assembly has the fitting for the HPCO switch aiming sideways towards the driver's fender, instead of straight up like the Ford original. With the HPCO installed and plugged in, it pulled the harness so far over that way that the wires to the compressor clutch were under a lot of tension. I did not want to try to get down in there and cut open a multi-armed harness monster and re-do it all, so I extended the clutch wires by 3" or so with soldered connections and heat-shrink tubing.

Then, all I had to do was put all the engine air plumbing back in, which should be easy... NOT! When I went to install the airbox (holds the air filter and PCV filter) and its intake tube, I found that the discharge hose of the manifold assembly was right in the way! How did that happen? Comparing to the old manifold assembly, the new one's discharge tubing from the manifold does not extend as low, and it tilts upwards, where the old one extended down further, and tilted downwards. The old one allowed the attached discharge hose to the condensor to pass under the intake air plumbing running to the airbox.

After playing with it, I ended up having the discharge hose running between the closely-spaced intake air duct and the filtered air to the throttle body duct. The hose touches one of them, nothing I can do about it. I hope in the hot days of July and August it doesn't melt the plastic. Let's see, a 300 PSI discharge would be 160 F or so so it would seem to be OK. Don't like having a hose that will move with engine torqueing rubbing plastic.

Out of all of the components for this complete system replacement project, there were ONLY 3 parts that did not require modification and fit correctly with no problem - The Denso FS-10 compressor, the orifice tube, and the HPCO switch itself! That's a pretty poor showing.

For most of these components, there are very few vendors. Many are made by the same company, just sold under different brand names.

TRB on Fri March 22, 2013 11:15 AM User is offlineView users profile

Many of the china products are not bad if sourced correctly.


When considering your next auto A/C purchase, please consider the site that supports you:

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