| [GMCnet] Duracool [message #133214] |
Sun, 03 July 2011 17:09  |
bdub
Messages: 1578
Registered: February 2004
Location: Central Texas
Karma: 5
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I just finished doing the recirc mod on my ‘76 HVAC box / firewall and
installed 3 cans of Duracool. At ~1500 rpm low side reads 14psi, hi side
runs 185psi. Outlet air is ~40° and blows hard. I’m thrilled.
Wondering about reports of a little less than 3 cans making 20#@ 1500rpm.
Should I try a little more to get the pressure up a little or leave well
enough alone? I kinda hate to press my luck. J
bdub
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'76 Palm Beach/Central Texas
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| Re: [GMCnet] Duracool [message #133229 is a reply to message #133214] |
Sun, 03 July 2011 19:03  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Billy,
After pulling a weak vacuum on mine I dumped in 3 cans of Duracool in and believe I saw 24lbs on the low side at about 1200 RPM. It was blowing cool, but I think if I dump it down to 15, or so, it will be cooler.
Oh, by the way I haven't yet done the recirc mod. Holy Cow does this thing suck a lot of air from under the hood. I've got to get to that. And the crossovers...
Larry Davick
Sent from my iPad
On Jul 3, 2011, at 3:09 PM, "Billy Massey" <bdub@bdub.net> wrote:
> I just finished doing the recirc mod on my ‘76 HVAC box / firewall and
> installed 3 cans of Duracool. At ~1500 rpm low side reads 14psi, hi side
> runs 185psi. Outlet air is ~40° and blows hard. I’m thrilled.
>
>
>
> Wondering about reports of a little less than 3 cans making 20#@ 1500rpm.
> Should I try a little more to get the pressure up a little or leave well
> enough alone? I kinda hate to press my luck. J
>
>
>
> bdub
>
>
>
> _______________________________________________
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] Duracool [message #133242 is a reply to message #133229] |
Sun, 03 July 2011 21:51 |
John Sharpe
Messages: 489
Registered: February 2006
Location: Texas
Karma: 1
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Senior Member |
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| Quote: |
.....installed 3 cans of Duracool. At ~1500 rpm low side reads 14psi, hi side
runs 185psi. Outlet air is ~40° and blows hard. I� thrilled.
Wondering about reports of a little less than 3 cans making 20#@ 1500rpm.
Should I try a little more to get the pressure up a little or leave well
enough alone? I kinda hate to press my luck.....
|
Billy, If you are satisfied leave it alone. Only consider adding more if it starts freezing up.
John Sharpe
Humble,TX
'78 Eleganza TBI
'89 Spectrum 2000 MPI V-10
'40 Ford Panel Delivery TPI
johnasharpe@gmail.com
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| Re: [GMCnet] Duracool [message #133248 is a reply to message #133242] |
Sun, 03 July 2011 22:26 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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| John Sharpe wrote on Sun, 03 July 2011 21:51 |
| Quote: |
.....installed 3 cans of Duracool. At ~1500 rpm low side reads 14psi, hi side
runs 185psi. Outlet air is ~40° and blows hard. I� thrilled.
Wondering about reports of a little less than 3 cans making 20#@ 1500rpm.
Should I try a little more to get the pressure up a little or leave well
enough alone? I kinda hate to press my luck.....
|
Billy, If you are satisfied leave it alone. Only consider adding more if it starts freezing up.
|
how can you tell if it is freezing or if the thermostat is set too low? mine keeps cycling the clutch every minute or so. if it is the thermostat how can i reset it? i read here that you can take the bulb off the evaporator and attach it to the low press. pipe and it will work fine.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] Duracool [message #133261 is a reply to message #133242] |
Mon, 04 July 2011 07:30 |
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Ok. I guess I'll know that it's freezing up if air quits coming out?
Thanks
bdub
-----Original Message-----
From: Behalf Of John Sharpe
Sent: Sunday, July 03, 2011 9:51 PM
Billy, If you are satisfied leave it alone. Only consider adding more if it
starts freezing up.
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bdub
bdub.net
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| Re: [GMCnet] Duracool [message #133296 is a reply to message #133261] |
Mon, 04 July 2011 12:46 |
John Sharpe
Messages: 489
Registered: February 2006
Location: Texas
Karma: 1
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Senior Member |
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| Quote: |
how can you tell if it(ac evaporator) is freezing or if the thermostat is set too low? mine keeps cycling the clutch every minute or so. if it is the thermostat how can i reset it? i read here that you can take the bulb off the evaporator and attach it to the low press. pipe and it will work fine.
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Fred, if the evaporator is freezing-up, air flow at the vents will decrease and possibly be non-existent. If the clutch is cycling, your pressure is probably dropping too low. Check the gauges when this happens, if it's below 20# add more refrigerant. Bring the stabilized pressure to around 20#. 20# at start-up or a hot coach probably indicates insufficient refrigerant charge.
If you suspect the icing switch (thermostat) is cycling the clutch then by-pass it and see if that's the problem. You normally only notice that the clutch is cycling on the icing switch when it seems to be blowing nice cold air and then cycles off for no apparent reason. The icing switch seldom if ever cycles the compressor on a GMC in south Texas. If it does, there is probably something wrong with the ac system. Other parts of the country with cooler temps and/or lower humidity will cycle on the icing switch more frequently.
I concur that placing the thermocouple on the low pressure line should still operate the icing switch to no ill effect.
John Sharpe
Humble,TX
'78 Eleganza TBI
'89 Spectrum 2000 MPI V-10
'40 Ford Panel Delivery TPI
johnasharpe@gmail.com
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| Re: [GMCnet] Duracool [message #133398 is a reply to message #133296] |
Tue, 05 July 2011 12:59 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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| John Sharpe wrote on Mon, 04 July 2011 12:46 |
| Quote: |
how can you tell if it(ac evaporator) is freezing or if the thermostat is set too low? mine keeps cycling the clutch every minute or so. if it is the thermostat how can i reset it? i read here that you can take the bulb off the evaporator and attach it to the low press. pipe and it will work fine.
|
Fred, if the evaporator is freezing-up, air flow at the vents will decrease and possibly be non-existent. If the clutch is cycling, your pressure is probably dropping too low. Check the gauges when this happens, if it's below 20# add more refrigerant. Bring the stabilized pressure to around 20#. 20# at start-up or a hot coach probably indicates insufficient refrigerant charge.
If you suspect the icing switch (thermostat) is cycling the clutch then by-pass it and see if that's the problem. You normally only notice that the clutch is cycling on the icing switch when it seems to be blowing nice cold air and then cycles off for no apparent reason. The icing switch seldom if ever cycles the compressor on a GMC in south Texas. If it does, there is probably something wrong with the ac system. Other parts of the country with cooler temps and/or lower humidity will cycle on the icing switch more frequently.
I concur that placing the thermocouple on the low pressure line should still operate the icing switch to no ill effect.
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thanks John.
what i see while driving is that the duct is blowing cold then suddenly blows warm then back to cold. it blows cold for about 5 minutes, warm for about a minute or less then back to cold. seems to have always done this.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] Duracool [message #133399 is a reply to message #133388] |
Tue, 05 July 2011 13:03 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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| emerystora wrote on Tue, 05 July 2011 11:27 |
On Jul 4, 2011, at 5:30 AM, Billy Massey wrote:
> Ok. I guess I'll know that it's freezing up if air quits coming out?
>
> Thanks
> bdub
>
Yes, all of a sudden the air will slow down and stop blowing from the outlets. Turn the A/C off but leave the blower on and soon enough of the ice will melt from the fins and you will have cold air blowing again. Wait until it starts to get warmer and start the A/C again.
If that happens then your charge of Duracool is too low. In high humidity areas such as Louisiana or parts of Texas you might need more than the 20 psi at 1500 RPM that I usually recommend. I once had mine charged at 15 psi and it was super coold in NM but our humidity is extremely low. My first trip toward Florida encountered freezing up of the evaporator. I raised the pressure to 120 and had no more problems.
Emery Stora
77 Kingsley
Santa Fe, NM
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i hope you mean you raised it to "20". i'm still on the low side, maybe between 15 and 20 it blows cold but the clutch cycles. air flow never changes.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] Duracool [message #133435 is a reply to message #133428] |
Tue, 05 July 2011 18:22 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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You can't use Duracool 12A on the roof units as they require Freon
22. There is a 22A version of Duracool but it is available usually in
the 20# cylinders or larger.
JR Wright
On Jul 5, 2011, at 5:59 PM, J A Holland wrote:
>
>
> Roof Air ~~ DURACOOL ?
>
> What is the procedure in changing the 2 Roof Units To DURACOOL ?
>
> ~ Joe ~
>
> --
> /_]*[__][] *[__|] ~ * '73 TZE063V101887 ""
> O---------OO--]* ~ '78 TZE168V100234 ""
> " Joe & Lavelle " ""
> 'sweet home alebamy'
>
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] Duracool [message #133442 is a reply to message #133388] |
Tue, 05 July 2011 19:39 |
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Will do, Emery.
I think your "120" in the second paragraph is a typo. Should that be 30#?
bdub
-----Original Message-----
From: On Behalf Of Emery Stora
Sent: Tuesday, July 05, 2011 11:28 AM
Billy Massey wrote:
> I guess I'll know that it's freezing up if air quits coming out?
Yes, all of a sudden the air will slow down and stop blowing from the
outlets. Turn the A/C off but leave the blower on and soon enough of the
ice will melt from the fins and you will have cold air blowing again. Wait
until it starts to get warmer and start the A/C again.
If that happens then your charge of Duracool is too low. In high humidity
areas such as Louisiana or parts of Texas you might need more than the 20
psi at 1500 RPM that I usually recommend. I once had mine charged at 15 psi
and it was super coold in NM but our humidity is extremely low. My first
trip toward Florida encountered freezing up of the evaporator. I raised the
pressure to 120 and had no more problems.
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bdub
bdub.net
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| Re: [GMCnet] Duracool [message #133454 is a reply to message #133398] |
Tue, 05 July 2011 21:33 |
John Sharpe
Messages: 489
Registered: February 2006
Location: Texas
Karma: 1
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Senior Member |
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| Quote: |
what i see while driving is that the duct is blowing cold then suddenly blows warm then back to cold. it blows cold for about 5 minutes, warm for about a minute or less then back to cold. seems to have always done this.
|
Fred, Guess you don't know the pressures when it cycles? You could just bypass the icing switch and see what happens. If that solves it, then you know the switch is working. Just need to figure out if it is truly icing (could be insufficient charge) or the thermocouple needs to be moved to another location.
John Sharpe
Humble,TX
'78 Eleganza TBI
'89 Spectrum 2000 MPI V-10
'40 Ford Panel Delivery TPI
johnasharpe@gmail.com
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| Re: [GMCnet] Duracool [message #133479 is a reply to message #133454] |
Wed, 06 July 2011 07:35 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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| John Sharpe wrote on Tue, 05 July 2011 21:33 |
| Quote: |
what i see while driving is that the duct is blowing cold then suddenly blows warm then back to cold. it blows cold for about 5 minutes, warm for about a minute or less then back to cold. seems to have always done this.
|
Fred, Guess you don't know the pressures when it cycles? You could just bypass the icing switch and see what happens. If that solves it, then you know the switch is working. Just need to figure out if it is truly icing (could be insufficient charge) or the thermocouple needs to be moved to another location.
|
it would cycle while i had the gauges hooked up. when the clutch dropped out the pressure went to 70#.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] Duracool [message #133483 is a reply to message #133479] |
Wed, 06 July 2011 08:18 |
John Sharpe
Messages: 489
Registered: February 2006
Location: Texas
Karma: 1
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Senior Member |
|
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| Quote: |
what i see while driving is that the duct is blowing cold then suddenly blows warm then back to cold. it blows cold for about 5 minutes, warm for about a minute or less then back to cold. seems to have always done this.
Fred, Guess you don't know the pressures when it cycles? You could just bypass the icing switch and see what happens. If that solves it, then you know the switch is working. Just need to figure out if it is truly icing (could be insufficient charge) or the thermocouple needs to be moved to another location.
| Quote: |
it would cycle while i had the gauges hooked up. when the clutch dropped out the pressure went to 70#.
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What was the pressure when it dropped? If it was below 25# I would add a little refrigerant, bring it up a few #s and see if that makes a difference.
John Sharpe
Humble,TX
'78 Eleganza TBI
'89 Spectrum 2000 MPI V-10
'40 Ford Panel Delivery TPI
johnasharpe@gmail.com
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| Re: [GMCnet] Duracool [message #133498 is a reply to message #133497] |
Wed, 06 July 2011 11:18 |
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This system has been non-operational since before 1998. Hasn't even had a
belt on it in 10 years. I found a couple gallons of mouse nesting next in
the air intake as well as by the evaporator. Replaced fan for blades ground
down by rubbing on debris.
I was surprised to get a slight puff of pressure with oil when I broke the
first dryer line loose. Changed dryer and expansion valve. Took the cores
out of the original R12 fittings and installed r134 adapters onto them.
Pulled system down to 30" with Harbor Freight air powered (venturi affect?
water aspirator?) vacuum pump. System was down 2.5" the next day and total
of ~5" the next day. Went ahead and charged with DuraCool anyhow. (Figured
once I got things circulating that the slight leak might heal itself.
(wishful thinking? we'll see.)) Ambient was probably 90° but coach interior
was 80° because I was running roof air. Was 100% recirculation air.
I'm looking forward to everyone's thoughts and advice. One thing I'm
suspect of is the fact that it didn't take all that long for the cheap
vacuum pump to pull the system down. Maybe 15 minutes. I released that and
did it again just because. I've no other gauge other than the one on the
A/C set that also came from Harbor Freight if that's accurate. I was also
surprised that it pulled it that far.
bdub
-----Original Message-----
From: On Behalf Of Emery Stora
Sent: Wednesday, July 06, 2011 10:24 AM
Out of at least 35 installs that I have done I have never seen three
cans give 30 psi. Unless your ambient temps are quite high I suspect
that you either were not completely evacuated or something else is not
quite right in your system. What was the ambient when you did the
install?
I believe you had told me that you were using a water aspirator to
provide vacuum. Those are not very good and you might still have had
some freon in your system.
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bdub
bdub.net
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| Re: [GMCnet] Duracool [message #133502 is a reply to message #133498] |
Wed, 06 July 2011 11:54 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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| Billy Massey wrote on Wed, 06 July 2011 11:18 |
This system has been non-operational since before 1998. Hasn't even had a
belt on it in 10 years. I found a couple gallons of mouse nesting next in
the air intake as well as by the evaporator. Replaced fan for blades ground
down by rubbing on debris.
I was surprised to get a slight puff of pressure with oil when I broke the
first dryer line loose. Changed dryer and expansion valve. Took the cores
out of the original R12 fittings and installed r134 adapters onto them.
Pulled system down to 30" with Harbor Freight air powered (venturi affect?
water aspirator?) vacuum pump. System was down 2.5" the next day and total
of ~5" the next day. Went ahead and charged with DuraCool anyhow. (Figured
once I got things circulating that the slight leak might heal itself.
(wishful thinking? we'll see.)) Ambient was probably 90° but coach interior
was 80° because I was running roof air. Was 100% recirculation air.
I'm looking forward to everyone's thoughts and advice. One thing I'm
suspect of is the fact that it didn't take all that long for the cheap
vacuum pump to pull the system down. Maybe 15 minutes. I released that and
did it again just because. I've no other gauge other than the one on the
A/C set that also came from Harbor Freight if that's accurate. I was also
surprised that it pulled it that far.
bdub
-----Original Message-----
From: On Behalf Of Emery Stora
Sent: Wednesday, July 06, 2011 10:24 AM
Out of at least 35 installs that I have done I have never seen three
cans give 30 psi. Unless your ambient temps are quite high I suspect
that you either were not completely evacuated or something else is not
quite right in your system. What was the ambient when you did the
install?
I believe you had told me that you were using a water aspirator to
provide vacuum. Those are not very good and you might still have had
some freon in your system.
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the 7525 manual says to vac. for 10 minutes. if you got 30" that should be enough. i let mine sit for an hour and the vac. rose just a bit. i too hope it will hold. i found the main leak and it seems to be holding; no oil visible around it.
Fred V
'77 Royale RB 455
P'cola, Fl
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