The 13.5 A/C will not cool rear bedroom on DP. What to do?

[jloftin60]

I live in South Louisiana where the summer time is very long, hot and humid.
My problem is after traveling, the rear A/C can not cool the rear bedroom. The heat from the diesel engine adds to the problem along with the 100* degree outside temperature.
I like a cold bedroom at bedtime. I have tried a fan, but no help.
Would it be worth installing a larger rear A/C 13.5 to a 1500 BTU?
The front A/C seems to cool ok.
What other ideas would work?

[wa8yxm]

Several things can be done to improve cooling, FIRST is a full preventavie maintenance run This includes removing both outer and inner covers on the condenser and cleaning it.. This in fact may be enough to fix your problem.

Also clean filters (inside) and if needed the evaporator (Do the filters first and inspect the evaporator once filters are removed)

Second. if you are on 30 amps with 2 A/Cs there are several methods to power both A/C's by using the 20 amp outlet, The standard cheater box will NOT work in modern campgrounds but might if the CG is old enough.

My method was to basically install a "Break out" for the rear A/C, I disconnected the power lead (Mine is a direct line from the circuit breaker to the A/C, yours may be different) and extended it to the outside, (A compartment) also ran a line from the original 20 amp breaker to the same compartment, an outlet on the "Breaker" side and a plug on the "A/C" side works like this.

A/C plugged in to the companion outlet. Standard as delivered operation.

A/C plugged into a 12 ga Extension cord Plugged into parks' 20 amp breaker = Operation of both A/Cs on 30 amp sites (in most cases)

NOTE: all added wires are 12ga in keeping with the 20 amp breaker. Note also, 12 ga extension cord recommended.

[CJW8]

Outside temp doesn't matter. Need to know the delta T between the AC inlet and outlet.

[dougrainer]

jloftin60 wrote:
I did check the temp coming from the vent, The outside temp was 96* and the inside vent temp was 74* with very little air volume coming from the vent.

Outside temp has nothing to do with the inside cold air output. What you want is the Temp Difference between the inside AIR return (filter) and the nearest to AC cold air output. Should be 18 to 22 degrees difference. Air return lets say is 95 input at filter. after a minimum of 30 minutes running the nearest cold air output should be 73 to 77 degrees. IF the inside of your RV was at least 85 degrees when you got 74 output, the AC is not cooling correctly. Volume may also be a problem. Have you had any work done on the AC units in the past? At this point, you NEED a Amp check of the Rear AC compressor. That will tell you if the system is charged and pumping correctly. Doug

[jloftin60]

I did check the temp coming from the vent, The outside temp was 96* and the inside vent temp was 74* with very little air volume coming from the vent.

[CJW8]

You haven't answered the question so we can't help you. Is it blowing cold air? Measure it. The air coming out of the vent should be about 20 degrees cooler than the intake. If not, you have a problem with the AC unit. If it is, then you have too much heat in the MH to get rid of.

[RLS7201]

Have you ever cleaned the condenser coil? Could be dirty and not allowing proper transfer of heat from the A/C unit.
Remove the vent in the bed room and with a mirror and flashlight, look for obstructions in the duct work.
Would it be possible to add another vent to the duct?

Richard

[mkirsch]

The rear AC is NOT directly in the bedroom, correct?

There is just a little duct running to the bedroom, correct?

Did this system ever work to your satisfaction in the past? If so something has changed.

What is the temperature of the air being put out by the rear AC unit?

Need to determine if it is a problem with the AC, or insufficient airflow.

A fan blowing into the room does not circulate the air, it just pressurizes the room. Some comes out above the fan, but it just gets sucked back into the room by the fan. Very little actual circulation. A fan pulling air OUT of the room may be more effective.

[pianotuna]

As soon as you stop place a large box fan under the RV pointing it at the by now hugely hot transmission and engine. You have several hundred pounds of hot metal and coolant that needs to be cooled off as fast as you can manage it. The engine alone weights about 1150 pounds. That is a big chunk of iron to cool down.

The insulation is a good plan as well but it may become saturated with heat.

I'm in a class C and in extreme heat I'll open the hood as soon as I stop. It does make a difference.

In my old diesel class C the dog house got so hot it would burn my right knee--so I added a foam pad that had a foil lining on one side.

Try running just the rear air conditioner while traveling so that it runs more or less constantly.

[imgoin4it]

I have a 13.5 acnd in my bedroom and could use the area to store hanging meat. It will get cold. I stick a dial thermometer in the outlet and get a reading between 40 and 50 degrees. I use it and a fan to help cool off the front of the coach. I think I would be checking to make sure the acnd unit was working properly.

[midnightsadie]

start by cutting down the heat, and a 14teen yr old unit just might be dyeing, check the out let temp. .

[ccxnola]

Look at adding some good double foil quilted insulation under the bed over the engine and around the sides of the bed box.
I did that and it made a fantastic difference.

[jloftin60]

I do run the generator and both A/C'S while traveling.
2002 Fleetwood Discovery with the air ducts in the roof.
One small vent in the bedroom roof. I wish it had more air
volume blowing through it.
Maybe the 14 year old A/C's need updated.

[dougrainer]

Need a lot more info. Year/Brand/Model of motorhome. Ducted or NON ducted. Your problem is the opposite of what most RVer's have. Due to the Bedroom having to turn over less volume of hot air, the bedroom AC usually makes it quite cold in the bedroom. Are you positive that the rear AC is cooling at all? going from 13.5 to 15 will not create a greater cooling factor. Will help a little but if NOT hardly cooling with a 13.5, then the extra 1500 will not help that much more for the cost.

[sch911]

Park in the shade.
Run both roof AC's using the generator while driving.
At night run the bedroom AC to a very low setting. Then during the day it'll have a chance to keep up.