Thermostat Issues

[mhilley]

I recently had the top end of my Dometic air conditioner replaced. The bottom end (cabin) was not replaced. I won't say who did the job but I had to take it back two times for leaks. It still leaks like a sieve when it rains. My question is - is there any way to adjust the interior cold control knob? The unit will never go below 74 degrees even on a cool day. With the "cold" knob set on 10 the compressor kicks on and off at 74 degrees. Help! Thanks in advance. Wish I had the old one back

[A W Warn]

Check the difference between the air temperature going in and the air temperature coming out of the AC. If the difference is around 15-18 degrees F, that's all an RV AC is supposed to do.

If the air is being cooled in that range, the only thing to do to make it better is either get into a shady area or add more AC capacity.

[mhilley]

I guess I didn't express myself well enough! If the temp outside is 80 degrees the a/c will only cool down to 74 degrees, which is only 6 degrees! If outside is 90 it will cool to 74, etc. The low end of the thermostat is set to 74. I need to adjust it somehow.

[crestonrv]

is ac still in pan ? sounds like pan was removed and if so was ceiling sealed to air flow ? this has knobs on ceiling ? if so and is not properly sealed may be recirculating cooled air and tripping t-stat. prematurely .

[nrgtrakr]

Top end replaced?
Did they replace the refrigerant?
Was the old refrigerant still legal?
If not, did they use the correct replacement?

[lewster]

Originally Posted by A W Warn

Check the difference between the air temperature going in and the air temperature coming out of the AC. If the difference is around 15-18 degrees F, that's all an RV AC is supposed to do.

If the air is being cooled in that range, the only thing to do to make it better is either get into a shady area or add more AC capacity.

Alan,

That's not quite correct. The stated performance specifications for Dometic (and RVP/Coleman) roof mounted air conditioners is called 'Delta T', or the difference between the air temperature at the return air grill and the cold air exhaust, which should be 18ºF-22ºF after the compressor has been running continuously for 12-15 minutes.

Remember, this is strictly interior air temperatures and HAS NOTHING TO DO WITH THE OUTSIDE AMBIENT TEMPERATURES. A properly operating roof unit will attain the required delta T regardless of the outside temperatures or where you are parked.

Of course, if you have sunlight pouring into your trailer, that will continue to heat the ambient inside air and will inhibit the cooling effect by continually raising the temperature of the return air to the roof unit. Even then, the delta T of a healthy unit should fall within the specified performance range.

[lewster]

Originally Posted by nrgtrakr

Top end replaced?
Did they replace the refrigerant?
Was the old refrigerant still legal?
If not, did they use the correct replacement?

No refrigerant to replace in a 2000 year Dometic A/C unit as it is hermetically sealed at the factory. If the unit leaked refrigerant, the 'upper unit' requires replacement. I would also have replaced the 'lower unit' inside the trailer at the same time for better performance compatibility.

If the performance is not within specifications, then either there is a leak of exterior air into the A/C unit (a distinct possibility as it IS leaking water ) or the intake section has not been properly sealed and isolated from the exhaust section, causing warmer air to mix with the air from the evaporator.

In either case, the OP needs to find a better installer who really knows how to properly place a roof unit on an Airstream!!!!

[nrgtrakr]

Thanks Lewster!