'83 Brave: Recharge dash A/C or not?

[BrewerBrian]

Sent: 7/16/2005

The "twofer the road" chassis air conditioner needs a new dryer and a new charge of freon. It's on a 1983 Brave with a Chevy 454 engine. We've looked through all the documentation we have and all over the engine area, but cannot find how much the system takes. (My guess is that some sort of label has fallen off.) Does anyone know how much Freon this systen takes?

Thanks in advance
Brian Walsh

[denisondc]

Sent: 7/16/2005

I dont know: but would think it would be about the same as a car or pickup - about 2 pounds of freon or slightly more. I would think you will also need to largely replenish the lubricating oil, especially since with a new dryer, you would need to pull a vacuum on the system to totally get the old moisture out, and some of the oil will come with it. I would expect you would need to charge it with freon based on the usual low and high pressure gauge readings for that type of system.
Being a 1983 it would have come with R12 freon in it. Do you know if it has been changed over to R134a?

[OldEdBrady]

Sent: 7/16/2005

No matter WHAT, I would change it over to 134a.  Freon is no longer manufactured in the U.S.  Sooner or later, you'll have to switch..So why not do it now before the price hits the stratosphere?

[BrewerBrian]

Sent: 7/19/2005

My A/C has not been changed over to the newer refrigerant. I know this because about 2 years ago I had to have some added and I remember that it was R12. The reason I was asking about the amount is that according to the mechanic, when completely recharging the system one needs to know the weight of freon to add. This amount is not able to be derived from the high and low pressure readings.

I have a friend who has offered me 6 cans of freon which he has in his garage. I think I'll take him up on the offer.

Thanks
Brian Walsh 

[denisondc]

Sent: 7/19/2005

Based on the ambient air temperature, there are charts that will show you the expected high and low pressure readings - but they arent the same for the different system setups. I.E. ford and mopar and GM have each used different systems over the years, and different from each other. So "charts" is plural. The readings also require some interpretation or interpolation. But if you can get one of those do-it-yourself books, and identify the type of compressor you have, you will probably find a chart that has what the readings should be, for different outdoor ambient temperatures. Also, measuring the surface temperature of the low pressure line and the high pressure line, and comparing it to a chart of the temperatures, would give you a good close result for adding freon. I think an experienced a.c. shop could do it just by hearing how often and how long the compressor clutch cycles off. That would only work with a system that used compressor clutch cycling for temperature control.
If you knew just how much R12 freon "by weight" to put in, it would be a simpler procedure, since you wouldnt need to take the ambient temperature into account, but I dont know that it would be a better way, and of course for recharging a partially discharged system, you still have to use the gauges and the charts and a thermometer. The "ambient" is the temperature of the air you are blowing into the condenser with a Large Fan pointed at the front of the idling vehicle. Essential I believe.
(R12 is one sort of freon, & R134a, R22, etc. are also, just different variations of the same family of hydrocarbon refrigerants.) You can learn a lot about the ins and outs at www.ackits.com.

[ClydesdaleKevin]

Sent: 7/21/2005

I thinking from reading these posts that I better win the lottery to replace the dash AC condensor/evaporator (whichever is the one on the radiator...lol) and recharge the system!  It seems quite a bit more complicated than I thought it would be with my hodge-podge system!

Kev

[denisondc]

Sent: 7/23/2005

Also: Kevin, before you spend whatever it takes to get the system working again, you need to find someone with a vintage motorhome who can tell you (or show you) if the dash a.c. cools the interior down enough to be worthwhile; and I dont mean cooling it from 85 down to 78, but rather cooling if from 100+ down to a temperature that is comfy with the windows closed, and only the a.c. fan moving the air past you.
Our roof a.c. is 13,500 btu, and will cool the interior to a comfortable temp when the RV is sitting still. Even so, parked in the sun when the air temp is over 100 (in the shade), it wont bring the temperature down as low as we might like it. We have always been comfortable in it though, as the humidity in New Mexico and Arizona is so low, and the air temperature in New Orleans hasnt gotten up past 95 on any of our summer visits. While driving the RV, with its sliding windows, and air leaks around the door and the floor drain openings, etc. -- we found it to be pointless to run the roof a.c. I just dont know how much better a dashboard a.c. unit driven by the engine would be.
We have had our old RV for over a decade, and I wouldnt install a dashboard a.c. unit even if it was free. I dont want to have to work "around" the extra parts.
We were parked for 8 weeks at my father-in-law's house in south Texas, but were in the shade of a medium sized live oak tree. The roof a.c. always kept it a comfy temperature in there, and the water the a.c. unit condensed from the inside air never stopped dripping from the roof.
When/If I redo my roof, I want to make the new one a little bit thicker and better insulated though

[ClydesdaleKevin]

Sent: 7/23/2005

So far, even on the hottest of days in direct sunlight, while parked our 13.5 btu Carrier will turn the Ark into an icebox if we leave it on "high".  This was even in 98 degrees in an open field. 

We've run it off the generator while driving on a couple of VERY hot days in slow moving traffic, but with the windows open, the vents open (we have the covers that allow you to keep them open even at highway speeds) and the AC dash fan on, it stays tolerable even on those VERY hot days as long as you are moving at a good clip...lol.  While the AC itself doesn't work, the fans and vents that go to it are, and they blow a LOT of air, even if it isn't cooled.

So, fixing the dash AC isn't a priority for us.  We might do it someday, when everything else is "done"...but its at the bottom of the list.

Kev

[calbrave]

Sent: 8/3/2005

"While driving the RV, with its sliding windows, and air leaks around the door and the floor drain openings, etc. -- we found it to be pointless to run the roof a.c."

Is this possible? I thought I could only run the roof a/c while I connected to shore power?
I think we got a bit of heat stroke this past week-end while driving around south of Calgary. (Saw what I thought might be a CWM on highway 7, maybe BigRock's? I was NOT allowed to stop and check it out)

[AllanCZ]

Sent: 8/3/2005

You need to have an on-board generator. Just fire it up and turn on the a/c. aahhhh......

> Is this possible? I thought I could only run the roof a/c while I connected to shore power?

[kd4pbs-1]

Sent: 8/5/2005

I don't know if this was touched upon, but I can guarantee you that you will not be satisfied retrofitting to R134a on something as large as a motorhome. For one, most of the older compressors can't take the higher discharge pressures involved. The condensor coils are made in a very inefficient "tube and fin" design instead of the neccessary "parallel flow" style that modern R134a systems use. All of the hoses will also need ot be changed to a barrier style hose, due to the much smaller molecules that R134a posess being able to leak out of the older rubber hoses. The large area that the AC unit will be called upon to cool will also cut down on it's effectiveness. I've done 3 R134a retrofits on vehicles in the last 10 years, each one of them done properly. One didn't work worth a hoot (1985 Dodge Caravan), One works mediocre (Dodge LeBaron convertible), and one works great (1984 Corvette). That's the difference? The Caravan had a tube and fin condensor and a large interior. Even though the compressor was an "r134a friendly" Sanden, it just wouldn't cool worth a flip. The LeBaron is only so-so because it has a black top, and being a convertible it has air leaks not found in a coupe. The Corvette is white, and has a very small cab space, a medium sized evaporator, and a very large condensor that is a more ideal 2-row small-tube serpentine design.

To answer the question of how much R12 to put in, charge in hot weather, full max AC until you don't see any more bubbles in the sight glass on the receiver/drier. If using guages on a system with no sight glass, any automotive A/C tech that is worth his salt will know how to read the guages along with a thermocouple temp sensor on the suction and discharge lines to get the superheat and subcool temperatures to determine adequate charge. If your tech does not know what "superheat" or "subcool" means, or has never heard of the term, find a different shop.
Good luck, and keep it R-12 if at all possible!

[Scorpionbmw99]

Sent: 8/11/2005

So just to be clear, if I want to run my roof duotherm while driving, I need to run it off the generator. Right?

[denisondc]

Sent: 8/11/2005

yes, to run the roof a.c. while driving, you need to have the genset running. That is what I have tried, and found its not worth it for us. It might make a passenger in the back of the RV feel a little better, but the driver hardly feels any coolness. I prefer just having all of the windows open.

[Oz]

Sent: 8/11/2005

And why is this?  If the side windows have the curtains closed along with the vents, etc and have any interior fans running, is the heat transfer through the front windows so bad that the air won't get cool?  You'd think it must be possible to run the roof A/C and have a comfortable air temp in the coach!

[denisondc]

Sent: 8/11/2005

By all means try it sometime, on a sunny day drive when the temperature in the shade is 90f or higher. There isnt much point in doing it when the air temp is only 80f or 85f though - thats hardly hot weather. In addition to the heat coming through the roof and window gaps, from the front of the engine cover to the aft end, there is a multi-kilowatt "heater", keeping the chassis and underfloor toasty warm.

Be sure and let us know how it goes.

[mightybooboo]

Sent: 8/11/2005

Mine cools  it down a bit and I have used it,but mostly I   dont bother with it.In screamin' hot weather it does make it more comfortable.But really not worth the effort.

BooBoo

[Lefty]

From: Im-still-Lefty

Timmy,
If your system still has a refrigerant charge, you'll have to empty it... now I'm not going to tell you how that could be done, it's R-12, and releasing it into the atmosphere is a very big no-no, but that's up to you... If it already is empty, then removing the lines and compressor would be simply a matter of unbolting, as another member said, make sure that the compressor mount isn't supporting another part. Lines can be loosened with 2 wrenches, They likely would be very tight after being untouched for many years. I would remove them at the evaporator under the dash, and pull them completely out. Capping would not be necessary unless you ever plan to replace everything in the future. removing the condensor in front of the radiator would be both a weight saving, and a cooling benifit. I would leave the evaporator, because it has minimal impact on the heater output, and removing it wouldn't be worth it., but everything else could definantely go.
Because converting to R-134a is easy when done right, and really not very expensive, I rarely suggest removing a system that is still complete, but not working, because most of the time, the compressor is still ok, just the refrigerant has all leaked out. O-rings are easily replaced, and air-powered vacuum pumps can be purchased for as little as $15.(Harbor Freight) . O-Ring and R-134a conversion kits run $30, including the ester oil, R-134a was about $5 a can last month. (takes about 5-6 cans for a full charge) a new drier would be around $25-30. So a complete retro would be around $100, if the compressor is ok. Add about $100 for a re-man compressor if it's not. Also, a qt. of flush is a necessity, you just pour it in one opening, and blow it out from the other. Another thing to think about is the hoses...new ones would have to be custom made re-using your old ends. Any automotive AC shop should be able to make them. R-134a requires "barrier hose" which is made of a different compound, and won't alow the smaller R-134a molecules to seep through. Without them, you would have to add R-134a periodically, as it leaks out. Probably no more than a can a year though. I've seen units that were working like they should, and they do help a lot. They won't cool a whole rig easily, but they will keep the drivers and passenger area fairly well cooled. And if left on Max-AC, can cool down the whole rig, in a couple of hours driving. Especially if you have tinted windows. But, the dash air unit will cause mileage to suffer (a little), and available power will be less (about 15hp-20hp) this isn't a problem with a 440, but a 318 would probably struggle. If running a genset and roof air instead, cooling the rig is usually much better and a lot faster, but the genset will use more fuel than running the dash AC would.

                                                                           Lefty

[HAL]

Sent: 4/9/2006

Just another thought. If the compressor is good and the system is just empty of R-12. I would just reservice it. There is a drop in replacement for R-12, it is hot shot. R-414. The servicing and pressures are just the same. Any HVAC service tec. should be able to service it for you.
I did my 79 Brave. the nice thing is you can mix the two. My was just low and now is blows 36 deg. air.
  HAL 

[DanielTBolger]

update whole thing to 134 it cheaper
http://www.oldairproducts.com/catalog

whole heating and AC unit or price right