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Old 08-29-2009, 06:30 PM   #1
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2000 31' Land Yacht
Central , Florida
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Improving dash A/C in a Class A for Southern Climates

I posted this on the RV.net group for a larger base for answers:
Replaced compressor, tech said it was the best they could do, "never will cool area, too big" he explained when on max, a/c uses cooled cabin air that is not cooled enough. Best temp at closest vent was 58 degrees on a 90 degree day. Cab was not cool.
Has anybody solved this problem?
Thinking about hanging a curtain behind front seats?
Another option would be reflective window film on side windows. Front already has it above line of vision.
Anything else, don't really want to run genset and house air for travel.
__________________________________________________ ___

Seems like from answers I got back running house A/C's while under way is common.

Here are some of the other replies.

1.If you have a heater shutoff valve leaking (Bypassing hot coolant to the heater) you will never get full benefit of your AC.
2.And even the slightest air leak from a doghouse cover will also kill cooling.
3.Also to help the AC you could wrap your AC hoses etc with some pipe insulation.
4.Removed the tube from the thermostat that goes into the evaporator fins. This will let the compressor run all the time but it may ice up on you.
Only when it's really hot out do I put up my windshield screen between the front slide outs to decrease the area cooled.
5.Before I stop for lunch I'll crank the generator (I leave the AC on so it will start when I start the generator) and run it until the dash AC is working well before shutting off.(not good idea, generator should be running smooth and warmed up before adding load)
6.We added a latch to the hall way door to keep it closed and now only cool the front half of the rig. We also added 2-8" diameter 120 volt fans (quieter and move more air than the old 12 volt fans)that we run with the inverter.

7.If you go the curtain route, you can get a number of different curtain traks styles at Curtain-Tracks.com
8. Add insulation under floor.
I can add things I have done.
I have already added insulation between dash and firewall, rerouted vent tubes, bypassed heat to a/c.

_______________________________________________
I am still looking for site with side window sunshades, did see a nice mesh rollup for a car window, white outside and black inside, but it was only 14 inches wide and I need 24 wide and about 30 long. Anybody here have any improvements not mentioned?
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Old 08-29-2009, 07:50 PM   #2
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Hi, basically you cannot make the dash A/C work any better than it's original design. But you can make it work better "if" it has problems. 28 to 40 degrees from dash vents should be expected. [varies by vehicle design] Sealing and insulation around the dog house is necessary. An A/C / heater blend door not closing properly will effect this. Some vehicles depend on the blend door to stop the heat from the heater core and some use a water valve. [some use both] Water valves have a built in leak to keep the coolant flowing. This helps extend the life of the heater core, but make your A/C work harder. I would add a positive closing water valve; You don't need the heater in summer. The dash air was designed to cool the driver and the cab, not the entire vehicle, so a closure or curtain would help a lot. Generator run roof airs work good while in motion too. Most generators are air cooled and don't need very long to warm up. [few minutes] Hope this helps.
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Old 08-30-2009, 09:25 AM   #3
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Bob,
A/c people said the best they could do was 48 degrees at the first vent. You are right as designed unit was for regular cab space, not a house. Problem with house a/c and genset running while underway is cost. Last trip was 2500 miles and driving time added up to about 80 hours, that would increase cost of fuel by 10% for main engine and about .5 gal/hr running genset. 25+40=65X2.50=162.50 more for fuel
Doghouse is well insulated by noise reduction but I will test temperature levels with ir thermometer for the entire cab once the curtains are up.

Right now I feel the tech's response to problem was hot air in the recycle mode will make the most difference for the investment of fix, two things will reduce temp of air returning to a/c : curtain and side window shades.
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Old 08-30-2009, 05:46 PM   #4
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Hi, for a short time in my carreer I was an A/C installer and repairman. [automotive] Some systems have an adjustable thermostat; we would set them at 28 to 32 degrees. [the thermostat is to stop it from freezing] This is the point where the A/C compressor cycles off and on. If your fan is on high, sometimes it won't get cold enough to cycle. Best test is to have your fan speed on low and watch a thermometer inside of register. The lowest temperature will be when it cycles. You can do this at higher fan speeds as long as the compressor cycles. At a high fan speed the warm air is doesn't allow the evaporator to cool down to this point. Use vise grips or buy a heater hose pincher to stop all coolant flow though your heater core and make the same tests; In most cases it will help. Systems that run constantly and don't cycle the compressor seem to run at 40 degrees at best. [suction throttling valve] Also is your condensor clean/clear and are your engine cooling fans working properly?
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2005 Safari 25-B
"Le Petit Chateau Argent"
[ Small Silver Castle ]
2000 Navigator / 2014 F-150 Eco-Boost / Equal-i-zer / P-3
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Old 09-02-2009, 08:32 AM   #5
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1990 36' Land Yacht
Bradenton , Florida
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[QUOTE=DaveFL;741415]I posted this on the RV.net group for a larger base for answers:
Replaced compressor, tech said it was the best they could do, "never will cool area, too big" he explained when on max, a/c uses cooled cabin air that is not cooled enough. Best temp at closest vent was 58 degrees on a 90 degree day. Cab was not cool.
Has anybody solved this problem?
Thinking about hanging a curtain behind front seats?
Another option would be reflective window film on side windows. Front already has it above line of vision.
Anything else, don't really want to run genset and house air for travel.
__________________________________________________ ___

Seems like from answers I got back running house A/C's while under way is common.

Here are some of the other replies.

1.If you have a heater shutoff valve leaking (Bypassing hot coolant to the heater) you will never get full benefit of your AC.
2.And even the slightest air leak from a doghouse cover will also kill cooling.
3.Also to help the AC you could wrap your AC hoses etc with some pipe insulation.
4.Removed the tube from the thermostat that goes into the evaporator fins. This will let the compressor run all the time but it may ice up on you.
Only when it's really hot out do I put up my windshield screen between the front slide outs to decrease the area cooled.
5.Before I stop for lunch I'll crank the generator (I leave the AC on so it will start when I start the generator) and run it until the dash AC is working well before shutting off.(not good idea, generator should be running smooth and warmed up before adding load)
6.We added a latch to the hall way door to keep it closed and now only cool the front half of the rig. We also added 2-8" diameter 120 volt fans (quieter and move more air than the old 12 volt fans)that we run with the inverter.

7.If you go the curtain route, you can get a number of different curtain traks styles at Curtain-Tracks.com
8. Add insulation under floor.
I can add things I have done.
I have already added insulation between dash and firewall, rerouted vent tubes, bypassed heat to a/c.

_______________________________________________
I am still looking for site with side window sunshades, did see a nice mesh rollup for a car window, white outside and black inside, but it was only 14 inches wide and I need 24 wide and about 30 long. Anybody here have any improvements not mentioned?

For what its worth, virtually all the coaches used to have a curtain track and curtain behind the driver/passenger seats. It is by far the most efficent way to help the dash air (and yourselves). Virtually all the dash ac packages were actually designed/sized for a pickup truck cab, and as such they can't handle an entire RV. The curtain lets it think its a pickup! A couple of dash mounted fans blowing on the captain and first mate will also help them feel cooler. Incidentially, 58 degrees at the vent does however seem higher that most properly functioning systems.
Good luck!
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Old 09-02-2009, 08:39 AM   #6
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1990 36' Land Yacht
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Quote:
Originally Posted by DaveFL View Post
I posted this on the RV.net group for a larger base for answers:
Replaced compressor, tech said it was the best they could do, "never will cool area, too big" he explained when on max, a/c uses cooled cabin air that is not cooled enough. Best temp at closest vent was 58 degrees on a 90 degree day. Cab was not cool.
Has anybody solved this problem?
Thinking about hanging a curtain behind front seats?
Another option would be reflective window film on side windows. Front already has it above line of vision.
Anything else, don't really want to run genset and house air for travel.
__________________________________________________ ___

Seems like from answers I got back running house A/C's while under way is common.

Here are some of the other replies.

1.If you have a heater shutoff valve leaking (Bypassing hot coolant to the heater) you will never get full benefit of your AC.
2.And even the slightest air leak from a doghouse cover will also kill cooling.
3.Also to help the AC you could wrap your AC hoses etc with some pipe insulation.
4.Removed the tube from the thermostat that goes into the evaporator fins. This will let the compressor run all the time but it may ice up on you.
Only when it's really hot out do I put up my windshield screen between the front slide outs to decrease the area cooled.
5.Before I stop for lunch I'll crank the generator (I leave the AC on so it will start when I start the generator) and run it until the dash AC is working well before shutting off.(not good idea, generator should be running smooth and warmed up before adding load)
6.We added a latch to the hall way door to keep it closed and now only cool the front half of the rig. We also added 2-8" diameter 120 volt fans (quieter and move more air than the old 12 volt fans)that we run with the inverter.

7.If you go the curtain route, you can get a number of different curtain traks styles at Curtain-Tracks.com
8. Add insulation under floor.
I can add things I have done.
I have already added insulation between dash and firewall, rerouted vent tubes, bypassed heat to a/c.

_______________________________________________
I am still looking for site with side window sunshades, did see a nice mesh rollup for a car window, white outside and black inside, but it was only 14 inches wide and I need 24 wide and about 30 long. Anybody here have any improvements not mentioned?
The curtains behind the "bridge" will give the most bang for the buck! Most all coaches used to have them for the same reason you have found, namely, the dash AC was actually designed/sized to a pickup cab and not a RV/house. Also, a couple of inexpensive dash or windshield mounted fans directed on the "crew" can make them feel more cool and comfortable.
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Old 09-03-2009, 04:28 PM   #7
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1996 clipper gas 34'
 
Blue Springs , Missouri
Join Date: Aug 2003
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my dash ac is ice ice cold, stock r12 system, everything working and this instead of r12
Refrigerant w/ Dye Can Details and Online Ordering at Enviro-Safe, Inc

icy icy cold. Put in my old BMW as well and its better than the original r12 in that car.
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