Anyone know how much Freon I need to fill the dash AC system on my 99 U320 36 ft.
Capacity for all coaches is 5.0 lbs or 80 ozs of R134A beginning in 1994.
Dash Air Conditioner Refrigerant and Oil Capacity (http://web.archive.org/web/20200111051919/http://beamalarm.com/Documents/dash_air_conditioner_refrigerant_and_oil_capacity.html)
Parker 3520-016 Receiver dryer (https://www.foreforums.com/index.php?topic=42919.msg431150#msg431150)
8 Lbs 134a in our coach is what reduced evaporator temp to minimum for me
Scott
Not very scientific but, I added until I started losing dash temp and that was with the low side reading 20 psi.
I really don't think it's 8 lbs of refrigerant, a 40-42 ft rig usually fits 5 lbs or 80oz. Oversize dryer would only increase capacity by an ounce or two. 5 lbs is quite a bit, most pickups only take 2- 3 lbs. 8 lbs would be overcharged and it won't cool well. if you could even get the system to take in all that extra refrigerant. The change from liquid to gas is what makes cool, if there's too much liquid, it can't change state and no cooling effect will happen.
Yes I couldn't believe the amount. So using a digital charging system I added 1/4 pound at a time and watched evaporator temperature and pressure were 15/275 keep adding till I actually was 9 pounds and temperatures weren't decreasing so I reduced back to eight pounds. 20/325 psi. 50 deg at 105 outside air temp. Last week running down the road was seeing 40 deg up in Ely back to Boulder City so I'm happy with what I got, but I completely agree a LOT of Freon. I will also state that I absolutely am unsure of the accuracy of the recovery system I'm using in regards to the digital scale. Overcharging r134 will quickly over stress the system and should be avoided. If you don't have access to a recovery charging machine you should have serviced by someone who does. The receiver dryer I mention is the same 12cu inch as removed.
Scott
This link to Sanden compressor, which is usually used in the ft motorhomes and other. I think this is the best information about ac systems I have ever found. It contradicts what many ac service professionals have told me about oil capacity, how to add it and how to determine exact amount needed. It's also a component test procedure like I've found no where else. https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.sanden.com/productlibrary/manuals/SD_Service_Guide_Rev_2.pdf&ved=2ahUKEwjV34L7hMjyAhUIXM0KHWcUCJIQFnoECAgQAQ&usg=AOvVaw1tI8v08Sc1MbnalbjuYz2w
Let me know what you all think.
Outstanding information. Would be nice if we had manuals for everything like this.
Scott
Followed y'all's suggestions of 5 pounds and it works great for my 96 U270 36'
We are in north Texas and it's 100 degrees everyday now. Did evacuate the system first and purchased 7 12oz cans. It will take 6.6 cans. Cools great but just wish the air flow from evaporator was better. Also looking to add some dash mounted fans to circulate air more on hot afternoon drives. Also had to replace the condenser fan relay. Relay would engage but contact burned.
My dash air never worked after purchasing a coach 3 years ago. Yesterday guy came late in the day to diagnose and fix it. First he vacuumed the system down although there was no freon left in the system and was able to hold vacuum for five minutes without changing. He next put in 5 lb of freon based on what I've read in the forms. There was no tag or anything anywhere to tell him. Cost me about $330. At the conclusion I had 40 degree air coming out of the register at the dash. They also put in an UltraViolet dye so if there is a leak I'll be able to find it with a UV light. I'm hoping this fixes my dash air problem because driving down the road without it in the summer is no fun
I thought about buying all the tools and equipment necessary to do it myself but really I don't have a whole lot of knowledge when it comes to this stuff otherwise I've done my reading and figured it would be better to just have somebody that knows what they're doing do it. I make come to regret that decision if this stuff leaks down again and I have to pay another three hundred bucks to refill but hopefully if there is a leak it will be found.
I still have a problem with my temperature control switch. There's seven wires on the back of that and nobody knows why. At least nobody that I've been able to talk to. I'm told that almost all of them have only three wires. When I was at fot couple years ago they told me they didn't have any more of those switches and the soldered wires directly to the back since there was a broken connector but the switch doesn't work as it's supposed to not sure why and I don't know how to find a replacement.
Still looking.
Vacuuming down the system is necessary it the system is empty to remove any
moisture. I have changed all the fittings in the rear of my coach as they where all
corroded. The original fittings were all aluminum and now the are steel. I will be filling
up my system in the next couple of days. I can fill my system but I don't have a vacuum
pump and my cousin has one and I will be there tonight.
Bob, that switch with 7 wires also controls the dash heater and that valve is only accessible from under the front of the coach. Look for the heater hoses going in and out of a plastic valve. and multiple wires going in it. Just to the center of the coach from the right above the headlights.
Thanks Chuck good to know. Any idea of where they get that's switch from? Instead of stopping n2n Mine just goes round and round and round sometimes I can get it to adjust temperature and other times it doesn't seem like it does anything at all.
Next time I go on to the coach so I'll look for that fitting you're talking about.
Need to rebuild my front six-pack soon.
That's why I did the headlight change when I did so I could get at the valve.
I was able to fix the valve but I can't remember what the problem with it was.
Just changed the condenser and dryer and replace the hose going from the dryer to the condenser there was oil dripping out of the old hose green I did some research on the forum and what I read I should be add some oil about 3 to 3 1/2 ounces I also had someone tell me not to add any but what I read I would lose about 1 oz in the old dryer and about 2 ozs in the old condenser I have two questions if someone can help
Can I pour the oil in to the new hose before connecting it to the dryer or should I vacuum it in on the high side and what type of oil and grade? 10 or 20 For this older couch (I read what type but have to look it back up)it's the grade I'm Concerned with it 10 or 20
This repair job has been going on for a couple of weeks waiting for parts so the system has been open to the atmosphere so how long do I vacuum it to get the boil the moisture out so I can add the Freon 134a about 5lbs 80 ounces I understand
I've read and Watch videos but can't find the answers
I used PAG 100 it is the medium viscosity. PAG is the required oil for R134
Takes 30 minutes of vacuum to get all water out. Better to get a can of oil and let the system suck it in then charge with the freon. Hopefully your new dryer hasn't been open to the air for a week. Depending on the humidity where you are could be bad.
Larry
It has Larry I installed the dryer on the frame and had trouble with the old hose so had to wait for a hose and I guess I didn't know better and it's open in a garage no humidity but probably damp with the rain we been having but open on one end to the atmosphere for about a week just got the hose today do you think I should order a new one
The last coach i charged was contaminated by the dryer being old and was decomposing and had also plugged the expansion valve. You mentioned changing the condenser was that for corrosion? Follow the compressor recommendations for charging oil type if you changed it. Having a Freon servicing machine that you can recover with is real nice. R134a went up in price a bunch the last time I ordered some. Ordered two 30lbs cans thinking the price would be around $130 each and was billed for $350 each. So some of the low turn over suppliers may still have at the lower price. Worth checking IMO.
Scott
Dryer might be ok just do one hour vacuum instead of 30 minutes to be sure. I've seen body guys leave them open in a dirty shop and they still worked, just better to always to keep sealed till hoses are on.
Larry
Book will probably say to change it. I keep sealed till I'm ready to install. Last dryers I purchased had a desiccant indicator on one of the plugs. Nice touch. Anyone's guess
Amazon.com: Universal Air Conditioner RD 8214C A/C Receiver Drier : Automotive (https://www.amazon.com/gp/product/B003R4TBDS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)
If the receiver/drier has been left open for any significant length of time then I think it would be best to replace it. At least that's what I would do.
Scott I change the condenser because the Finns had swelled out from rot and stopped the fan from turning , had it checked on the road this summer so they vacuum it out for me because I didn't have a recovery machine at home , I ordered a complete unit condenser ,fan,and dryer from Foretravel and had it shipped to Canada. Installed it myself but the dryer was mounted up on the frame of the coach, so for it to fit to the long hose coming from the evaporator I had to remount it on the frame . I am a newby at refrigeration and didn't realized that the dryer had to be kept sealed as much as possible.which I went to automotive school in the 70s I am a red seal auto mechanic here in Canada and they probably taught me that in school but Ac wasn't my field and that was many years ago in the pass It's been open to the atmosphere for a good week now in an enclosed garage if you think it's ruined it maybe a good idea to change it if I vacuum it for a hole day would it dry it out
I would still use the drier and pull a vacuum which would remove any moisture. Couple of hours should dry it out but a longer vacuum wouldn't hurt anything. Recommended to keep the drier sealed until ready to install to keep trash and moisture out.My dash ac blows 32 degree air consistently in the desert and have seen it dip below that on occasion. I need the colder air because in 96 and older the systems volume of air was less. I keep a produce probe thermometer in my vent and when it doesn't blow in the 30's I tweak. I check periodically with an infrared thermometer..Having as many units as I've had over the years I know that to have one this old to blow this cold is unusual but no complaints from me as it gets mighty hot in my part of the country and points southwest where I frequent.
You can get compressor oil in pressurize cans.
Proper measurement of evacuation of an AC system requires a Micron gauge. A standard set of AC gauges is not sensitive enough to measure success. Micron gauges usually start at 20,000 and measure down to 200. ASHRAE recommends evacuation to below 1000 microns for moisture removal and below 500 microns after replacing a compressor. Some equipment manufacturers call for evacuation to 400 microns to ensure that harmful water vapor is removed from the system. Asking how long you should evacuate the system is like asking how low it takes to pump the water out of your basement. That depends on how big the basement is and how much water is in it.
Incomplete evacuation causes sub-optimum performance and premature system failures. There are plenty of examples cited where proper methods were not used and yet the system ran mostly well for some years, just like there are plenty of people who run 15 year old tires on their RVs. However, That doesn't mean old tires are the standard. I could go into the physics about this but most peoples eyes glaze over when I start...... LOL!
There is more than enough info on the internet that is certainly wrong on this subject. The paper cited from Sanden is simply wrong on evacuation. I am sure they know what they are speaking about CONCERNING THEIR PRODUCT but should have consulted someone else on evacuation.
If you are going to do your own work, buy a micron gauge and use it.
TOM
Rick- Just my $.02 FWIW
Buy another receiver/drier and log the experience as another "lesson learned". Evacuating your questionable drier does nothing; baking it does little to renew it either.
When you evacuate your system for recharge you may want to do what the "better" shops do; namely, use the "triple evacuation" method. Even with my 2-stage pump with 75 micron capability, I used this method. It was what I told my DIYer friends to do ..... especially when they were (often) using a rented vacuum pump.
1. Evacuate the system
2. Break the vacuum to approx 1 atm with refrigerant
3. Repeat (1) and (2)
4. Evacuate the system again and charge to specs.
Good luck on the fix, and safe travels to ya.
Ed Sievers,
Rinky-dink SOB owner
Denver, CO
X2
Ive tried baking desiccant and leaving in a good vacuum and my results were never to my expectations .
Ed and Scott I ordered a new dryer it was only $40 will be here in a couple of days it was a inexpensive lesson and cheaper then contaminating the new Freon and running into trouble I look at it this way by trying to do the work myself Im saving big dollars than having some shop do and in joying it the cost of replacing the condenser assembly and hose It was rusted all the bolts pretty well broke had too re-drill all the holes thanks for all the Advise everyone . It was a good thing that I asked these questions and it was pointed out There a lot of experience on this form and everyone has a good point hope to run into all of use on this forum love hearing all the knowledge and advice
Where did you get the condenser? Mine appears to be leaking and is on my short list of repairs.
Keith
Hi Keith I order it from Brad LangFord parts manager 936 564 8367 ext 173 at Foretravel Texas it was a complete assembly condenser electric fan and dryer all in one unit I believe it was around $650.00 not sure would have to check bill of sale best way is to email him partsvendors.texas@foretravel.com he'll give you a quote he's very good at getting back to just give him time just give him all the information on coach and what you need
I am not home today when I get home I can look up the bill of sale for the part number
Rick