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1978 Buick Skylark R134a Conversion-Questions

mrdap on Sun October 18, 2009 6:57 PM User is offline

Year: 1978
Make: Buick
Model: Skylark
Engine Size: 231 CI
Refrigerant Type: R134a
Ambient Temp: 93
Pressure Low: 25
Pressure High: 190
Country of Origin: United States

Hello,

I just converted my 1978 Buick Skylark 231 CI V6 from R12 to R134 and I have some questions
This is a CCOT system with a thermostatic cycling switch, not a pressure cycling switch.

New AC Delco R4 compressor (not remanufactured)
New Omega accumulator
Condenser and evaporator flushed
New GM white orifice tube
New HNBR o-rings
All hoses rebuilt with new Goodyear barrier hose and crimp fittings
Ester oil 8 oz. (factory GM Buick service manual calls for 5.5-6.5 oz. Instructions that came with the compressor call for 8 oz.; that is what I went with)
Evacuated with a new vacuum pump for about 1 hour
Charged with 2.090 lbs of R134a from a drum using electronic scale (system calls for 3.5 lbs of R12, so 60%)

Conditions:
Ambient temp = 93 deg F
MAX AC
HI fan
Windows open hood open
Engine RPM = 1,330

Compressor is not cycling
Low Press = 30 lbs
HI Press = 265 lbs
LH Center duct temp = 53.4 deg F
Engine RPM = 1,330

Next I put a large fan in front of the condenser. Here are the results:

Compressor is not cycling
Low Press = 25 lbs
HI Press = 230 lbs
LH Center duct temp = 49.0 deg F
Engine RPM = 1,330

Next I sprayed a little water on the condenser. Here are the results:

Compressor is cycling
Low Press = 22 - 53 lbs
HI Press = 210 - 170 lbs
LH Center duct temp = 53.0 deg F (varies with cycling)
Engine RPM = 1,330 – 1,700 (varies with cycling)

Next I turned the fan to Low. Here are the results:

Compressor is cycling
Low Press = 22 - 51 lbs
HI Press = 220 - 165 lbs
LH Center duct temp = 49.3 deg F (varies with cycling)
Engine RPM = 1,330 – 1,700 (varies with cycling)

Next I set the engine speed idle (650 rpm). Here are the results:

Compressor is not cycling
Low Press = 25 lbs
HI Press = 190 lbs
LH Center duct temp = 45.4 deg F
Engine RPM = 650

Compressor is noisy, makes “Popping” sounds

Here are my questions:

1. Are my pressures correct?
2. Do I have enough R134a charge?
3. Since the performance is very good (I’m getting a 47 degree decrease in temp. from ambient), I don’t mind that the compressor is not cycling at a stand still. On the road it does cycle. Do you agree?

And the big question is:

4. What is the popping noise at idle and how do I get rid of it? It only happens at idle. When the RPM is a bit above idle, it never happens.

Thanks in advance.

mrdap

iceman2555 on Sun October 18, 2009 9:27 PM User is offlineView users profile

The system is seriously undercharged! A good starting point for a retro is 85-90% of factory charge rate. Add app 4 oz to accommodate for the amount necessary to pre-charge the hose/manifold system. Get the system charged properly and then re-post conditions.
A good method to insure proper charge rate and does not rely upon pressures (inadequate at best) is a temperature measurement between the inlet and outlet of the evap.
Operate the vehicle in the following conditions:
MAX COOL
HIGH BLOWER
DOORS OPEN
ENGINE AT IDLE
Allow the system to operate for app 5-7 minutes. Then measure the inlet (cool side of orifice) and outlet (prior to accumulator) sides of the evap. The temps should be the same or within 3-5 degrees of each other. When condition is met the system is totally charged. Then evaluate the system (pressures) for proper operation.
It is a very good possibility that the noise produced by the compressor will not go away. The damage has already occurred and will not be rectified by the completion of the recharge and subsequent lubricant flow.
The lubricant used for this compressor is a bit lite. It is known that many like the use of POE (esters) but this is a 100 centistroke lubricant and the R4 is spec'd for a 135-150 centistroke lube. This alone may contribute to possible R4 noise issues. The R4 is a noisy compressor to begin with, but the use of a lite lube may exacerbate this problem.
With this serious undercharge condition, the compressor is probably operational will very little lubricant in the case. The lube has fallen from suspension and has settled in evap. It will not move from this location until the system is totally charged.
Failure to charge the system completely will result in compressor failure (total).



-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

mrdap on Sun October 18, 2009 9:55 PM User is offline

Ice man,

Thanks for the response.

What I didn't post was that before I charged to 60% I started with 85%. I added one ounce from there and the duct temperature went up. So I felt it was overcharged. Then I developed a leak in one of the schraders that had a cap on it. It was a cheap cap and the tip of the schrader protruded just enough that when I tightened down the cap, it depressed the scharader. Once I got a good cap with a recess in the bottom, that leak was fixed. Then I discharged, re-evacuated and started with 60 % charge with the intent of adding an ounce at a time until the best performance was achieved. The performance was much better than with 85 %. I added an ounce and waited for the system to stabilize. The duct temp had dropped about 1/2 deg. So I thought I had the sweet spot there. I didn't post all this because of confusion factor.

At any rate I will add some R134a and see what happens to both the noise and the performance.

Thanks

mrdap



Edited: Mon October 19, 2009 at 1:46 AM by mrdap

mk378 on Sun October 18, 2009 11:01 PM User is offline

In addition to what Iceman said, it appears your condenser airflow is inadequate. This leads to undercharging because with a proper charge the high side will be quite high and performance with the car sitting still will be poor. It's not so much of an issue on the road. The fan clutch is probably worn out and not spinning the fan as fast as it should. Also make sure the fins on the radiator and condenser are clean and all the stock shrouds are in place.

The R4 would really prefer a heavy oil like PAG 150. Unfortunately, ester seems to be only sold in 100 weight.

mrdap on Mon October 19, 2009 1:44 AM User is offline

Iceman,

Also forgot to say, unfortunately, it is impossible for me to measure the evap inlet temp (right downstream of the orifice tube) on this configuration becuse the whole evap inlet tube is wrapped with insulation tape, part of which attaches the thermostatic cycling switch probe to the tube.

Thanks

mrdap on Mon October 19, 2009 1:51 AM User is offline

mk378,

Thanks for the response.

All OEM factory shrouds are in place with no cracks and it has the factory AC seal around the top off the radiator support. Condensor fins are totally clean.

The fan clutch is relatively new but is standard duty. I would like to buy a HD or Severe Duty unit, but they don't seem to be available for this application. I was going to scrounge the junkyards for a larger application that will bolt to my water pump and then buy a new HD cluth for it.

Any other ideas on finding a HD clutch?

Thanks

iceman2555 on Mon October 19, 2009 3:51 PM User is offlineView users profile

It was stated that the condenser was replaced, could you please post type and construction material.
The ThemoCycling switch should be located on the evap outlet not the inlet.
Do not install a 'severe' duty fan clutch, you will be confronted with an excessive amount of fan noise and possible loss of engine performance/fuel mileage. Use the hvy duty thermostatic unit.
Seeking to recharge by vent temps and pressures is not an acceptable practice. This procedure has been part of AC folklore for many years. This procedure would work somewhat with the older compressors that maintained a crankcase lubricant charge, but will not work with the modern AC system. The system must be charged to the correct amount of refrigerant and then evaluated for performance. If performance fall below expectations at this point, then a complete diagnosis of the system is required to determine the lack of cooling efficiency.
Get the system properly charged and then evaluate the system, not the reverse.
Good luck!

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

JACK ADAMS on Mon October 19, 2009 4:06 PM User is offline

He says the evaporator and condenser were flushed not replaced. I would say that the old 10mm tube and fin just won’t cut it with cooling. Need more like a Universal Parallel Flow Condensers, that will be much more efficient. This will help with the high head pressures. Hope this helps and good luck.

mrdap on Mon October 19, 2009 4:54 PM User is offline

Iceman,

Beg to differ with you, but the thermostic switch probe is attached to the evap INLET right after the O-tube. This is not a VIR or POV it is a CCOT. There is no way to attach it to the outlet because the outlet is just a tube nut the attached to the accumulator.

Condensor was not replaced, it was flushed and is in good condition.

You say to use a HD thermostatic clutch. Can you recommend a source? The only one I can find is a STANDARD DUTY thermostatic clutch.

As I said earlier would add charge. I stepped it up from 60% to to 85% in 5% increments and then the last final charge to 87%.

I will post results for daytime heat ASAP

All testing done so far was at night.

In general, the results so far have increased duct temperatures, pressures are about the same, popping is reduced, but not eliminated.

I will post the details ASAP.

In general I agree that the condenser performance is lacking wolud like to add airflow, I have not been able to find a HD fan clutch, only standard, which is what I have now, fairly new.

Also, now, when on the open road at 65 mph duct stabilizes at about 50 deg at 75 amb at night, then when I stop at a light, duct temp goes DOWN to 46, then back up to 50 at speed. Seems to be the reverse of what I would expect.

Thanks

mrdap

mrdap on Mon October 19, 2009 4:57 PM User is offline

Jack,

Thanks for the link to the condenser. I may have to go that way if I can't get it sorted out. Up till now the performance was good and perfectly acceptable in the desert

My problem is the compresser noise. Sounds like marbles banging around in there. Only at idle in gear though.

Thanks

iceman2555 on Mon October 19, 2009 9:46 PM User is offlineView users profile

Sorry for the mis reading of the 'condenser' issue....ole eyes clouded by freon gases.
I shall check tomorrow, however, the ThermoSwitch is normally located on the outlet of an evaporator. It's purpose is to prevent evap freeze up by cycling the compressor. Locating the switch on the inlet side would allow for total evap freeze up prior to compressor cycle. Of course, I could be wrong...has happened before.
I noticed a post on another site...and the 'prof' states that your change is correct at 65%....and this was determined by an evaluation of pressures. Pressures on a retro fitted vehicle are almost meaningless.... as a determination of system charge rate....they leave much to be desired. 134a operates at a much higher high side pressure than 12...by as much as 25-35%. Considering your posted ambient temp of 93 degrees...at this temp, the posted pressures indicate, to me, a serious undercharged system. Given the performance of a weak fan clutch, a very inefficient condenser and then 'supposed' high side pressures could be 300 psi or greater.
The only method to know exactly what pressures are for this or any other system is to completely recharge the system to OE specs. The system must be totally and fully charged. The temperature test indicated earlier is a very good method to insure proper recharge...esp for a retro when an unknown amount comes into play. Once the system is totally charged...using temperatures....and forget about the pressure aspect...get the system charged completely...then evaluate pressures.....if they exceed pressures that your find comfortable....then add additional cooling efficiency to the system...DO NOT REMOVE REFRIGERANT!!! Keep in mind..pressures that a system requires has nothing to do with what your or any other tech finds comfortable or acceptable. The system must be totally charged correctly....first and foremost this must be accomplished. If elevated pressures are encountered after complete recharge...then address the heat transfer issue...not the refrigerant level issue.
Your vehicle was available with a CCOT or a ThermoStatic Switch. Why not simply replace the TSW with a Pressure Cycling Switch and test the temps as suggested.
Keep in mind that both of these control devices are designed to accomplish the same thing....cycle the compressor to prevent evap freeze up.....and the LPCO switch is located on the evap outlet side. Considering the age of this vehicle...it is possible that the switch was installed incorrectly at some time in the past.
Lack of lubricant is the #1 generator of compressor noise issues.....and over charged system...or excessive discharge pressures (restricted condenser) are also a source.
One other aspect of compressor noise...which usually is a notice of things to come for the compressor....like total failure...the #1 cause of compressor failures is lack of lubricant....and the #1 cause of lack of lubricant in the compressor is lack of sufficient refrigerant or refrigerant flow with in the system.
Keep in mind, also, that an evap that is not cooling properly (properly charged) will not produce an acceptable vent temp. If the system lacks sufficient refrigerant to properly cool the evap....it will not produce the expected vent temps.
Adding a bit here...removing a bit there....run for awhile....add...or remove as desired.....if the system is not charged properly....there is not lubricant flow to the compressor....and it will fail..no 'ifs' 'ands' or 'buts' to it...without sufficient refrigerant to move the lubricant from the evap back to the accumulator and then to the compressor....it will starve for lubricant and will simply....STOP WORKING!!! The evap must be flooded to insure this lubricant movement.....equal temps inlet and outlet....works every time.

Good luck!

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

mrdap on Mon October 19, 2009 10:25 PM User is offline

Iceman,

I appreciate you help.

However, I have to ask, did you read my post? I have increased the charge to 87%, that is a bit over 3 lbs of R134a on a system designed for 3.5 lbs of R12.

Please don't take offense, but I have to say that you keep repeating about "charging it correctly" and how useless pressure readings are. So what is the correct R134a charge for a 1978 Buick? As far as I can tell, there is no one "correct charge" for a R12 to R134 conversion. There are only guidelines and starting points from which the optimum charge is determined for a particular system. This is determined by making measurements. The measurements are pressure and temperature.

Also, once again, this vehicle is equipped with a CCOT system WITH a thermostatic switch not “OR” a thermostatic switch. And it is located (from the factory) on the INLET side of the evaporator. Perhaps you have never worked on a vehicle this old, but I suggest you get your facts straight before you insist others are incorrect. I have posted a page from the factory Buick manual that describes the system.

78 Buick Manual

Also, I CANNOT measure the evap. inlet temperature without disassembling the system and removing the FACTORY installed insulation tape that covers the ENTIRE inlet pipe (minus the first inch where the orifice tube is). I do not intend to do that.

I see no point in replacing the thermostatic cycling switch with a pressure cycling switch. The beauty of the thermostatic switch is that it measures temperature, therefore it will keep the evap. from freezing independent of the refrigerant used.

You spent a lot of words explaining that if I don’t have enough refrigerant the oil will not flow to the compressor. If you had read my last post you would have seen that I am beyond that now, I have increased the charge to 87%. The compressor IS getting lubricant now.

I test drove the vehicle today and it performs very well with duct temperatures between 45 and 49 degrees F at 65 mph and between 49 and 55 degrees at idle in drive on a 90 deg. day. I will post the pressures shortly as soon as I have time.

My problem now is getting rid of the noise. It has been reduced and only occurs at idle, if I raise the engine RPM just slightly, it goes away.

Or do I need to throw away the compressor and start with a new one?

And where I can find a HD fan clutch, or ideas for an alternate application fan/clutch assy. that would fit my water pump. That is what I could use some help with now. That is the purpose of the forum, right?

Thanks.

mrdap


Edited: Mon October 19, 2009 at 11:50 PM by mrdap

HECAT on Tue October 20, 2009 9:11 AM User is offline

Quote
Originally posted by: mrdap


Please don't take offense, but I have to say that you keep repeating about "charging it correctly" and how useless pressure readings are. So what is the correct R134a charge for a 1978 Buick? As far as I can tell, there is no one "correct charge" for a R12 to R134 conversion. There are only guidelines and starting points from which the optimum charge is determined for a particular system. This is determined by making measurements. The measurements are pressure and temperature.

Also, once again, this vehicle is equipped with a CCOT system WITH a thermostatic switch not “OR” a thermostatic switch. And it is located (from the factory) on the INLET side of the evaporator. Perhaps you have never worked on a vehicle this old, but I suggest you get your facts straight before you insist others are incorrect. I have posted a page from the factory Buick manual that describes the system.


The proper charge weight is the R-12 specified charge. With no changes to the stock set up, this refrigerant quantity is required for proper lubrication migration. Converting to R-134 requires the same amount of refrigerant to perform adequate oil migration. Reducing the R-134 refrigerant quantity by 10 or 15% will sometimes show improvement in lower vent temps and lower high side pressure, but this is done at the sacrifice (and risk) of proper system lubrication. You are now at 87%, stay there. As you stated that this did reduce some compressor noise, critical lubrication has been improved. However, irreversible damage may have been done due to the lack of proper lubrication when operating at a 60% charge. Pressures and temperatures (including drop across the heat exchangers) can now be used to test performance and identify what changes could be made to improve R-134 performance such as parallel flow condenser and improved air flow.

Since Iceman stated he would have to check specifics on your vehicle, and he could be wrong; (IMHO)I would suggest you get your facts straight before you make accusations. We are all here to help and offer our suggestions based upon the collective many years experience, and the many many sad sad stories of failed conversions. We will not support the conversion "folklore" and the drop in "magic in a can" solutions; we will only offer solutions to do it right. Of course, you don't have to agree or follow those recommendations.


-------------------------


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

FLUSHING TECHNICAL PAPER vs2.pdf 

mk378 on Tue October 20, 2009 9:26 AM User is offline

If you can't measure evaporator inlet temperature (though really you'd only need to make a small hole in the insulation for a thermocouple probe) you can estimate it from the low side pressure. Compare saturated temperature in the evaporator to evaporator outlet temperature. This is the "superheat" method of charging. A CCOT system should operate with near zero superheat. In other words, liquid refrigerant is present all the way through the evaporator and some spills out into the accumulator.

Another thing to tinker with is the orifice tube size. Some people try one size smaller OT to keep the flow of refrigerant about the same despite the higher high side pressure with R-134a.

bohica2xo on Tue October 20, 2009 2:11 PM User is offline

Quote
Originally posted by: HECAT
The proper charge weight is the R-12 specified charge.

There. We are done.

All of the labor, frustration, poor performance - is directly related to using a refrigerant the entire system was not designed around.

Conversions rarely are simple. Most never reach OEM performance. Unless you live in a country where R12 is not available, there is just no good reason to convert.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

iceman2555 on Tue October 20, 2009 2:17 PM User is offlineView users profile

No offense taken!
The issue with working on cars this old......naw...not gonna go there!!!
This vehicle platform was supplied with either a LPCO switch or a ThermoStatic switch.....(not both) depending upon production date. As stated earlier, both are designed to perform the same function. After some research...looking at some very old manuals....it appears that the switch could be located in either position. Both control devices are set for the same parameters.
It is possible for the ThermoSwitch to be placed on the INLET and will function there...providing the system is TOTALLY and PROPERLY charged. Once more, the issue of recharge is the most important factor in determining AC performance diagnosis. Pressures are a test tool to use after the system is properly charged to properly evaluate total system performance..not just the AC system but engine cooling also.
Since a CCOT system functions with a 'flooded' evap the inlet and outlet temps should be the same....or within 3-5 degrees of each other. If the system is properly charged...at that point the placement of the ThermoSwitch becomes moot. The switch is designed to cycle the compressor at app 32degrees. Given that the properly charged system has an inlet and outlet temp the same...the switch works as designed to prevent evap freeze up.
The down side of placement at this point is that under certain conditions, the pressure/temp at the orifice tube outlet may be less than 32 degrees and this would result in a cycle point of the compressor. This condition is very evident on some model vehicles that utilize a smaller orifice tube. One of these conditions is an undercharged system...where one may experience a pressure/temp drop at this point due to lack of total refrigerant. However, this condition will be rectified once the system is totally charged. This position could actually result in a loss of cooling efficiency (vent temps) by premature cycling the compressor prior to the evap having sufficient refrigerant to actually perform system cooling.
The location of the switch...either one...on the outlet of the evap or accumulator produces a more realistic idea of evap performance.
Just a 'tidbit'....OE engineers do not use pressures as a guide line to determine system charge rates...they use temperatures at given points in the system...much as has been posted by others.
If you wish to not access the evap inlet...that is your decision...however, know that it is virtually impossible to actually determine system charge rates by pressures alone. Given that a refrigerant change is also part of the equation....a refrigerant that the system was never designed to operate with and the possibilites become much more difficult. Take the time....do the work correctly....it will pay off.
50%....65%.....86.35689%.....99 %...it makes not difference...the system must be charged correctly. On this system...the evap must flood....if it takes 100%...it takes 100%....pressures be damned....the system operates under certain conditions....the evap must flood. It should be flooded under the highest heat load....MAX AIR....DOORS OPEN....ENGINE @ IDLE....HIGH BLOWER. This is the greatest heat load on the system...if it works under these conditions...it will work at 1500 rpm....2000 rpm.....25000 rpm. This condition must be met....if not...the compressor will starve for lubricant.....and it will get noisy....and it will stop working. It is a simple design of the CCOT system.
The issue with the fan clutch. Heavy duty vs standard duty. The only difference between these units is the amount of resistance in the clutch itself. Both engage at the same temp...normally about 175 degrees air temp. This temp is determined by measuring the air temp between the radiator and face of the fan clutch. To test this requires a method to measure air temp and a small hole in the shroud. Normal fan clutch slippage (@full engagement) is app 75 % fan speed to water pump rotation speed. A fan clutch should never completely disengage. A heavy duty fan clutch has less slippage factor...normally about 80% fan speed to water pump rotation speed. This enables an extra amount of air to be moved over and thru the condenser/radiator. This also produces one of the greatest customer complaints....NOISE. When air moves...it is noisy.
After checking with several clutch mfg'ers....there is only one clutch (standard duty) offered for this vehicle. However, it would be possible to research spec's for this clutch and probably locate a different fan clutch. One needs only to determine the correct measurements for this clutch and 'go looking'. Most all earlier model GM vehicles utilize the same water pump attachment sizes and the bolt circle for fan attachments are the same. The major differenced is the length of the shaft....yours is app 2.03 inches. Might check for a possible match with a V6 truck. The v6's offer the longer shaft size.
The correct fan clutch for your vehicle (if you have the correct unit) is also used on several V8 engines, including a 400 cu.in used in 71-72 Chev Trucks. The correct fan clutch should be sufficient for your V6.
However, a much simple approach would be to install additional cooling performance by the use of an aux electric cooling fan located on the condenser. This could be connected to a pressure switch that would activate the fan at a give high side pressure or could be wired so that the fan operates any time the compressor is engaged. Personally, prefer the first since additional cooling is not normally needed at high way speeds.
Another approach and may also require the aux fan would the, as Jack stated, would be a replacement condenser. Changing to a more efficient condenser will do wonders for a retro fit.....and does a great job of dropping vent temps.
Good Luck!!!
Almost forgot....check the placement of your fan within the fan shroud....app 1/2 of the blade should be OUTSIDE the fan shroud. This may not be a problem...but have seen this issue crop up in the past.

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

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