A6 A/C Compressor Oil Capacity and Electrical Connector Position

[kna4977]

In the process of replacing a/c compressors. The new one says it’s prefilled with 3 ounces of oil. Has PAG oil from what I’ve read. Is this enough or how much should it have? 72 C60 system going to R134. R12 capacity on decal says 3.25lbs.

Also the electrical connector for the clutch on my old compressor is at the 10 o’clock position. The new one is at the 2 o’clock position. Can this be changed and if so how?

[weq92f]

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The conversion charge for your capacity is around 2.6lbs of R134a. You'll need to flush or replace the condenser and evaporator then add a couple ounces to each of the same PAG oil in your compressor. That's about 7 total ounces. Original R12 oil capacity was...??? Probably 10 or so...maybe someone has that spec.

There are charts online that will give you R134a pressure guidelines so that you can finalize the amount of charge using gauges rather than weight of refrigerant.

Clocking the electrons plug...no idea.

Hth,

-Kevin

[Steeveedee]

For the harness, I'd run it as-is if the wires reach and they can plug in strain-free.

[howzzzit]

Factory service manual says 10 ounces of oil for R12. The compressor sump plus what's out there traveling around with the refrigerant.

[Stocker]

Found in my old notes from when my A/C system was changed from R12 to R143a:

R12 = 3.75# (60 oz.) + 10 oz. mineral oil

R134a @80% = 48oz. + 8oz. PAG oil

[kna4977]

Originally Posted by Stocker

Found in my old notes from when my A/C system was changed from R12 to R143a:

R12 = 3.75# (60 oz.) + 10 oz. mineral oil

R134a @80% = 48oz. + 8oz. PAG oil

Thanks! It already has/had PAG and Ester Oil in it. I'll drain the old and new compressor and refill the new with the amount that came out of the old one. I was able to get a puller from the parts store, removed the clutch and pulley and turned the coil to the correct position.

[weq92f]

Originally Posted by kna4977

Thanks! It already has/had PAG and Ester Oil in it. I'll drain the old and new compressor and refill the new with the amount that came out of the old one. I was able to get a puller from the parts store, removed the clutch and pulley and turned the coil to the correct position.

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While you have it on the bench, break it loose before install (turn the pump shaft). I've had new pumps that took enormous effort to spin the first time.

-Kevin

[kna4977]

I've replaced the old A6 compressor with a new A6. I drained the oil out of the old one and it essentially had no oil. Maybe an ounce or so. Drained the oil out of the new compressor and got nothing out. I put 6 ounces of oil in the new compressor and installed it. Vacuumed it down. No leaks. Started to charge. At first no issues. Put about a can and a half of R134a in. Was still on high idle, so decided to kick it down to normal idle. Started squealing (probably the belt) will re-tighten and adjust once it cools off. Pressures seem good nothing out of the ordinary, but I hear some piston noise and when engaged, it puts a significant load on the engine and the RPMs drop quite a bit. Is this normal or should I be concerned and if so, what should I do?

[PbFut]

I went through a lot of the same issues you are having about 2 1/2 years ago. There is so much conflicting information it is difficult to get the correct data. I am not sure this info will be 100% correct, but it is what I ended up with. Draining the "factory oil" out of your new or rebuilt compressor is smart. I used a medium level viscosity PAG oil the first time and lost a compressor within a few months. The second compressor got PAG 100. No issues since. In my area, the AC runs nearly year around. Use your gauges to figure amount of 134 needed, and stay true to those gauges. Lots of small variables will affect amount of oil and refrigerant needed. Within reason a small amount over on the oil is way better than too little. You figured out how to rotate the magnet. Be sure the diode is on your harness lead. Last point. There is a rear not so arched bracket that attaches to a mount on the intake manifold. Be sure you are using it. The compressor has a tendency to tip in a small amount without that rear bracket and the belt will wear on its edge. You will wear a belt out in about a year without that rear bracket and loose it at the most inopportune time. These are my observations and findings. Yours may differ. Enjoy the cold air.

[weq92f]

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The RPM pull down at startup is normal. Not to say yours isn't excessive but if the pump is reasonably quiet and the system is cooling at good pressures, it probably isn't.


-Kevin

[425HP409]

To change the connector location you have to remove the hub and pulley and then it can b rotated.

[kna4977]

Originally Posted by 425HP409

To change the connector location you have to remove the hub and pulley and then it can b rotated.

Yes I did that. The pressures are temperature dependent and change as heat rises while the engine continues to run and generate more heat as I continue to charge, but I believe they are in range. Temperature was right at 110 degrees. Low side was at 55 and high side was in the low to mid 300s. The compressor got more quiet as it continued to run and more refrigerant was put in. I'm still not satisfied with the vent temps, 40s to 50s and sometimes 60s but maybe it's doing the best it can or maybe my standards are too high and I'm wrong to compare vent temps from a 50+ year old R12 to R134 system to a brand new R134 system that is putting out temps in the 30s under the same conditions.

[Stocker]

Originally Posted by kna4977

I'm still not satisfied with the vent temps, 40s to 50s and sometimes 60s but maybe it's doing the best it can or maybe my standards are too high and I'm wrong to compare vent temps from a 50+ year old R12 to R134 system to a brand new R134 system that is putting out temps in the 30s under the same conditions.

Just throwing out a couple things I remember from when my A/C was converted to R134a after being dead for many years.

A mechanic told me that my A/C should only be expected to reduce ambient air temp by 20 degrees. I said that by that logic, with outside temp at 100, you think 80 at the vents is normal & acceptable? He thought about that and backpedaled.

I either read (or was told) R134a is supposedly a less efficient refrigerant than R12. If that's the case, why does an R134a system use only 80% as much refrigerant as an R12 system? Seems like it should be the opposite.

Oh well, it's more important that it works than it is for me to understand it all.

[kna4977]

Originally Posted by Stocker

Just throwing out a couple things I remember from when my A/C was converted to R134a after being dead for many years.

A mechanic told me that my A/C should only be expected to reduce ambient air temp by 20 degrees. I said that by that logic, with outside temp at 100, you think 80 at the vents is normal & acceptable? He thought about that and backpedaled.

I either read (or was told) R134a is supposedly a less efficient refrigerant than R12. If that's the case, why does an R134a system use only 80% as much refrigerant as an R12 system? Seems like it should be the opposite.

Oh well, it's more important that it works than it is for me to understand it all.

General rule of thumb I have read is about 30-40 degrees lower than outside temperature. This would mean that my system specs out as "normal".

I have some other systems I've redone and/or converted in other vehicles and they get much cooler under the same conditions.

[weq92f]

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If it is blowing 40 it's good. It should not slowly warm to 60 then back to 40. Any cycling of the temp would be minimal...say within a 5 degree range.

With pressures on H/L in normal range (yours seem to be good...maybe high on the low side slightly at 50) for ambient and vent temps around 40 I'd say you're done. Test at 1500 RPM and keep condenser air flow at max during the test.

If your vent temps fluctuate 20 degrees during operation....something is amiss I'd say. When it gets near 60 vent temp, is the compressor still pumping? Maybe you have an over/under-pressure causing the pump to shut off?

An R12 condenser is not going to function as well as a more modern, parallel flow unit. Make sure you have plenty of air flow on the condenser...check the heat distribution within it as well when things get up to temp.

Hth,

-Kevin

[kna4977]

Originally Posted by weq92f

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If it is blowing 40 it's good. It should not slowly warm to 60 then back to 40. Any cycling of the temp would be minimal...say within a 5 degree range.

With pressures on H/L in normal range (yours seem to be good...maybe high on the low side slightly at 50) for ambient and vent temps around 40 I'd say you're done. Test at 1500 RPM and keep condenser air flow at max during the test.

If your vent temps fluctuate 20 degrees during operation....something is amiss I'd say. When it gets near 60 vent temp, is the compressor still pumping? Maybe you have an over/under-pressure causing the pump to shut off?

An R12 condenser is not going to function as well as a more modern, parallel flow unit. Make sure you have plenty of air flow on the condenser...check the heat distribution within it as well when things get up to temp.

Hth,

-Kevin

They don’t necessarily fluctuate 20 degrees. Usually the 60s readings are on the outside vents when I open the door. Influenced by outside air. If I move to the center vent it’s much cooler. 40s-50s. Compressor doesn’t cycle. Always on and working when a/c is on.
Condenser air flow is minimal. Vehicle is sitting inside a garage on high idle and charging with low air flow.

[Stocker]

Originally Posted by kna4977

Usually the 60s readings are on the outside vents when I open the door. Influenced by outside air.

Any chance the A/C Air Shut-Off Valve (flapper) in the pass. side cowl isn't working properly? See page 182 https://media.lmctruck.com/pdf/CB/cbComplete.pdf

[weq92f]

Originally Posted by kna4977

They don’t necessarily fluctuate 20 degrees. Usually the 60s readings are on the outside vents when I open the door. Influenced by outside air. If I move to the center vent it’s much cooler. 40s-50s. Compressor doesn’t cycle. Always on and working when a/c is on.
Condenser air flow is minimal. Vehicle is sitting inside a garage on high idle and charging with low air flow.

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First, vent temps are not "influenced by outside air" by opening the car door. Vent temps come directly from the evaporator....the air is "cooled" their and pumped through the ducting to your vents. All of your vents should read within 5 degrees of each other....no exceptions....especially given the run length of your ducting under the dash. If you read 60 on one vent and 40 on another from the same system, your ducting has a massive leak and is sucking in hot surround air (or you are not measuring vent temps correctly).

Condenser air flow is necessary. I installed a dedicated fan onto mine and wired it to be controlled by the pressure switch. When the high pressure line reaches 254 PSI, the trinary switch engages the electric condenser fan. The fan will cycle back off when the pressure has dropped to around 220 PSI thus causing the fan to cycle with pressure during slow speeds/low-airflow-over-condenser conditions. Once airflow is sufficient to keep high side pressure below 254 (say highway speed), the fan remains disengaged.

Keeping those pressures from going too high will keep the head pressure reasonable and allow the system to effectively and efficiently remove heat from the passenger cabin.

If left unchecked, the pressure in the system can become too high and result in poor cooling performance at best and hardware failure at worst.

Test it again...this time force a bunch of air through the condenser and watch that "low to mid 300" high side pressure get down to 250 or below and your vent temps drop.

Hth,

-Kevin

[leddzepp]

R-134 has never worked for me in a system that was originally designed for R-12. I wasted more time and money chasing cold air. Now I just use r-12 as the system was designed for and enjoy ice cold air in 100 plus degree heat sitting at an idle in traffic.

[weq92f]

Originally Posted by leddzepp

R-134 has never worked for me in a system that was originally designed for R-12. I wasted more time and money chasing cold air. Now I just use r-12 as the system was designed for and enjoy ice cold air in 100 plus degree heat sitting at an idle in traffic.

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In my area there's lots of R12 available from 40-50 dollars per 12 ounce can. 2 or 3 cans for a charge at max 150 bucks total for the gas! That is doable still and better/cheaper than swapping condenser, poa/exp valve and whatever else on a R12 to R134a conversion.

-Kevin

[kna4977]

Originally Posted by Stocker

Any chance the A/C Air Shut-Off Valve (flapper) in the pass. side cowl isn't working properly? See page 182 https://media.lmctruck.com/pdf/CB/cbComplete.pdf

No it works fine and I'm not sure how much of an impact that valve would actually have. I am wondering about the heater valve though. It is new, but the hoses feel the same temperature wise going in and coming out. Is that normal? I would think the one going from the engine to the valve would be hot and one going out and into the heater core would be cooler?

[weq92f]

Originally Posted by kna4977

No it works fine and I'm not sure how much of an impact that valve would actually have. I am wondering about the heater valve though. It is new, but the hoses feel the same temperature wise going in and coming out. Is that normal? I would think the one going from the engine to the valve would be hot and one going out and into the heater core would be cooler?

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If the valve is closed there's no coolant flowing and so the hose is going to be ambient temp until it gets close to moving hot coolant (the intake or water pump area). Sounds to me like the valve is preventing flow of coolant to the core.

EDIT: unless the hose is hot to the touch going into and out of the valve....in which case, it is not closing. (I recently had to replace the potentiometer in my dash A/C controls, the one that controls the valve, as it had failed...leaving the valve open)

-Kevin

[kna4977]

Originally Posted by weq92f

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If the valve is closed there's no coolant flowing and so the hose is going to be ambient temp until it gets close to moving hot coolant (the intake or water pump area). Sounds to me like the valve is preventing flow of coolant to the core.

EDIT: unless the hose is hot to the touch going into and out of the valve....in which case, it is not closing. (I recently had to replace the potentiometer in my dash A/C controls, the one that controls the valve, as it had failed...leaving the valve open)

-Kevin

The heater valve on the right inner fender well both the hose going into it and out of it are the same temperature when running at operating temperature. I checked that valve (which is fairly new) and it will hold vacuum but it loses it slowly so that may be one problem. I think the valve is stuck open or partially open allowing hot coolant to flow through the heater core when the a/c is on. What's the best way to test these things? The valve that's on the passenger firewall that allows or prevents fresh air from entering tests fine and holds vacuum.

[weq92f]

Originally Posted by kna4977

The heater valve on the right inner fender well both the hose going into it and out of it are the same temperature when running at operating temperature. I checked that valve (which is fairly new) and it will hold vacuum but it loses it slowly so that may be one problem. I think the valve is stuck open or partially open allowing hot coolant to flow through the heater core when the a/c is on. What's the best way to test these things? The valve that's on the passenger firewall that allows or prevents fresh air from entering tests fine and holds vacuum.

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When I knew the thing was malfunctioning, I suspected the valve was bad. When it finally stuck open, I pulled the hoses off of it to confirm it was open then started diagnosing and found that it was more likely the 6 dollar potentiometer in the dash control switch (Vintage Air) and so replaced that first. Sure enough, that was the problem.

In your case, I would bypass the heater core completely by looping the heater core feed line back into the heater core exhaust line and just run it like that. You'll know if it made a difference. Otherwise...if the hoses going into and out of the valve are both hot then I'd say you're right...it's stuck open.

-Kevin