Duracool Question

Carl Stouffer

Carl Stouffer

Well-known member
Jan 15, 2009
4,670
352
83
Tucson, Arizona 85718
I know CR-12A (Duracool or equivalent) is popular for use in our coaches, but I have a question for other applications. The common info on charging
the GMC system is to charge it ti 15 - 20 psi on the low side with the engine at 1500 RPMs at an ambient temperature of about 85 degrees, right?

Does this method apply to other vehicle applications as well? Hopefully Emery will see this and reply.

The reason I am asking is that I have been running it in my XJ Cherokee for a number of years now (at least 5 or 6) and I just can't seem to get good
cooling out of it. Maybe I am expecting too much out of it in 100 plus degree temps. If I have the charge too low, the compressor shuts down due to
low pressure, and if I add some, it doesn't seem to cool as well. I tried putting the proper amount per the conversion tables, but still can't seem
to get the charge right.

Thanks, I could use some advice here.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
Carl,
This is just a SWAG, but you might have a tired compressor. I don't know what the high side pressure should be with Duracool, but either Emery or the
Duracool website may tell you. In any case, the high pressure pipe going into the condenser should be about 150 degrees F or better when charging it
as described.
HTH
Rick Staples
'75 Eleganza (with Duracool and a second evaporator that COOLS!)

--
Rick Staples, '75 Eleganza, Johnstown, CO

"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
 
Try 25-30 low side psi the suction line should be cold to the touch and sweaty 15 to 20 in most cases will leave you short of a full charge on most
vehicles.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
In different applications I've had to replace the low pressure switch to one with a lower pressure rating Carl. I've been using a form of this
refrigerant for close to 20 years and have always found over charging seems to have a real detrimental effect on cooling.
Hal
--
1977 Royale 101348,

1977 Royale 101586, Diesel powered,

1975 Eleganza II, 101230,

1974 Eagle Bus 45',w/slideout,

Rio Rancho, NM
 
> In different applications I've had to replace the low pressure switch to one with a lower pressure rating Carl. I've been using a form of this
> refrigerant for close to 20 years and have always found over charging seems to have a real detrimental effect on cooling.
> Hal

So, apparently there are lower pressure switches that will fit? I had a 2000 Buick that would not work with Duracool. The compressor would not come
on until about 35 psi on the low side. A lower pressure switch could have allowed me to make the change. Ended up putting 134 back in.
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
What year XJ? They span the R12 and 134a years. I have a 99 with 250k on It and is ice cold using tbe 134a it was designed for. I pumped it down and
used the exact weight of 134a on the sticker. No more or less. I would study your radiator fans. I had one with the electric fan where you would turn
on the AC and the fan came on as designed. Then after 10 mins and heat soaked the e fan shut off. Replaced. Then be sure your shroud is in place and
REALLY test your fan Clutch. Mine got lazy this year. It appeared ok with the "free wheel test" but never engaged as RPM increased it just continued
to free wheel and not really move air. I put in the ZJ clutch from NAPA. Moves tremendous air and has great low speed cooling but costs 1 MPG. The
good news is I discovered NAPA clutches are USA and this translates to the 3 GMC part numbers in the interchange as well. These might he a good GMC
choice over Chinese. I found the old XJ clutch to have the thermal spring caked with road grunge. I cleaned by flushing with WD and will try it in the
fall to see if I can save gas during winter. Again air flow over condenser is crucial.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Good suggestions. It is an '87 XJ Laredo, with a 4.0L engine that had been converted to 134a shortly after I bought it. The compressor has about
80,000 miles on it. The electric radiator fan appears to be working properly, but I have not really looked at the engine driven fan clutch. That
could be part of the problem as the AC works less efficiently at idle in traffic.

I will check the pressures again tomorrow and am anticipating the outside air temp to be 90+ by the time I get to it. Does ambient temperature affect
the pressure? If so, how?

It is possible that the compressor is a bit tired, but it is a Sanden and only has about 80,000 miles on it.

Maybe a lower pressure switch would help, so I could keep the pressures at around 15 - 20, or maybe I need a higher low side pressure. That's what
I'm trying to find out.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
See what low /Hi pressures you are getting. If high side is good your compressor is good. If it stays running your switch is ok. If this is orifice
tube type and someone convertered that for 134a you may need the R12 type. Higher ambient temps raise hi and low side pressures. I have R12 charts
and 134a charts but no HC12 charts as I have not used that.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
> In different applications I've had to replace the low pressure switch to one with a lower pressure rating Carl. I've been using a form of this
> refrigerant for close to 20 years and have always found over charging seems to have a real detrimental effect on cooling.
> Hal

Most vehicles have those pressure switches installed as loss of charge switches and are located in the high side liquid lines. A true low pressure
switch would be located in the low side in the suction line. If the system had a loss of charge switch that was rated for say 50 psi and the suction
pressure was 25 psi with the compressor running it won't cycle the compressor off because the control is located in the high side liquid line that
doesn't see low side pressure but if you are very low on refrigerant it will trip because the pressure in the liquid line could be below 50 psi. That
is the low pressure that opens the switch.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
John Sharpe and I put DuraCool in my 1995 Jeep Grand Cherokee (V-8) years ago and it works fine. Unfortunately I'm not sure how much we put in. IIRC
we used 20 psi on the low pressure side.
--
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
 
Follow-up:

I replaced the fan clutch on the XJ Cherokee and added another can of Duracool. I'm not sure I still have the charge right, but the low side was at
about 30# (at 100+ O-A-T). The high side line was running at 200 degrees plus and the suction side was sweating up and was cold to the touch.

What I did certainly made a difference, I don't know whether it was primarily the fan clutch that made the difference in airflow across the condenser,
or the additional refrigerant. It ran cooler on the way home from work today, and I guess I can't really expect the air coming out of the dash
registers to be much cooler than 60 degrees when the ambient temperature is 108. :roll:

Thanks for all the ideas and advice.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
Carl.
Check your low pressure on a cooler day.
When it’s 75 to 80 outside I would suggest filling it to about 20 psi with the air conditioner on high and RPM about 1500.
If it’s set at 20 psi then on a hotter day it will probably read 25 psi or higher, so your 30 psi, even though it seems high to me, might be alright if it’s 108 out.

Duracool is quite different from R12 or R134a in that a lower charge will make your air conditioner run colder. In fact a charge of 15 psi will often have an air output close to 32 degrees. The only problem with that is that moisture in the air will freeze on the coils and soon block the airflow. So we put a bit more in to prevent the freezing of the evaporator coils.

Emery Stora
77 Kingsley
Frederick, CO

>
> Follow-up:
>
> I replaced the fan clutch on the XJ Cherokee and added another can of Duracool. I'm not sure I still have the charge right, but the low side was at
> about 30# (at 100+ O-A-T). The high side line was running at 200 degrees plus and the suction side was sweating up and was cold to the touch.
>
> What I did certainly made a difference, I don't know whether it was primarily the fan clutch that made the difference in airflow across the condenser,
> or the additional refrigerant. It ran cooler on the way home from work today, and I guess I can't really expect the air coming out of the dash
> registers to be much cooler than 60 degrees when the ambient temperature is 108. :roll:
>
> Thanks for all the ideas and advice.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Dumb questions but is your electric fan working whenever the compressor clutch is engaged and is your clutch fan fan shroud in place. Also be sure
your e fan runs after some miles. I had one where it would check good in the garage then thermal and quit after 10 mins. Ok back to GMCs.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
> Dumb questions but is your electric fan working whenever the compressor clutch is engaged and is your clutch fan fan shroud in place. Also be sure
> your e fan runs after some miles. I had one where it would check good in the garage then thermal and quit after 10 mins. Ok back to GMCs.

Yes, yes, and yes.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
Considering the osa is 108 your pressures are about right. In my opinion you are not overcharged. Thirty lbs suction is about where you want to be.
Certainly not 20 lbs which would be under charged.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
Roy
Unless you indicate what engine ROM and the ambient temperature your statement that 20 psi would be undercharged could be misleading.

Several of us that have installed many, many systems with Duracool over many years commonly use 20 psi at 1500 RPM at ambient temperatures below 85 degrees. At higher ambient temperatures the same volume of charge will give a higher pressure. For a GMC motorhome with the original A-6 compressor that would be 3 six ounce cans of Duracool or slightly less.

Emery Stora
77 Kingsley
Frederick, CO

>
> Considering the osa is 108 your pressures are about right. In my opinion you are not overcharged. Thirty lbs suction is about where you want to be.
> Certainly not 20 lbs which would be under charged.
> --
> Roy Keen
> Minden,NV
> 76 X Glenbrook
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Thanks Roy. It works well when the OAT is below 100.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
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