I sounds like you have a system that was not properly designed in the first place so you will have to be creative to make it work for you, if you close off vents in one room you will send more air to the rest of the house but you are also effectively increasing attic space and I would imagine your the airflow in his room was not designed to handle that. The basic problem is that your controller is probably on the first floor and it is satisfying and the unit is shutting off while the upstairs still needs cooling, you can combat this by turning the fan on ON to continually circulate air even when the thermostat is satisfied (it is relatively inexpensive a fan motor does not draw that much electricity)and you can adjust the air volume to all your downstairs supply vents to not provide as much conditioned air in the space where the controller is this will cause the unit to run longer and hopefully cooling th upstairs. If the system was installed correctly there will be dampers on the each branch line as it exits the main trunk line if not you can adjust the supply grilles down but this is not as effective and it creates air noise. The proper way to do it is either have two systems or zone dampering with two individual controllers but both these options are more costly obviously Here is a link that might be useful: Air Conditioning Repair made easy

well Dave, I see that the contractor posted his findings so I wouldn't worry too much about upsetting or offending anyone. it isn't unusual for there to be conflicting opinions, but the fact is that you and he are the only ones who have seen the ductwork. his discription of your return air setup is suspect. I see he is advising you to wait out the summer to do any duct/return modifications. if you can, do. it is awfully hot to be modifying ductwork this time of year. a rushed job isn't a good job. better someone take the time to properly install and seal ducts. it kinda bothered me that no mention of duct or return sealing was mentioned. of course the discussion is pretty technical. but I find that leaky ducts/returns are often overlooked. when you talk about the kids rooms and the 3-4 temp difference, you mention west facing windows. how many & what approx size are in each room? what type of windows do you have? single pane, double pane? metal frames, vinyl frames? clear glass or low-e glass? if the temp difference is due to the west windows..and it would be here in my area, then there are a couple of things you could try. block the afternoon sun from the exterior for a day or two and see if this evens out the 3-4 degree temp difference. wouldn't have to look great, or be permanent, just stop the solar gain. if you can keep the heat from entering the house, then the a/c doesn't have the added load to temper. exterior shading is the best route. rather than interior shades & curtains. beat the heat before it gets inside. if this works then invest in solar screens. yes they are darker than normal screens, but they will minimize heat gain. if windows are double paned..you can't install window tints as it will increase heat between panes and blow the seal. awnings and bahama shutters are other options but to me..at this point solar screens would be more cost effective. right now you have more time than solutions, so give it a try. don't worry about riling those guys up..they live for that stuff. Shophound & the guys have a good handle on things, so let them talk themselves around. I have to admire your restraint & patience. you are aware that 1" pleated filters are very restrictive? for now I'd change to a less restrictive filter. at least then more air will return to the unit. hang in there. best of luck.

Contrary to convential wisdom, venting an attic does little to reduce the temperature of the exterior roofing material and therefore has virtually no effect on the useful life of the roofing. (see "Roofing Failures" by Carl G. Cash) You might ask why asphalt shingle manufacturers void warranties if the roof is not vented and the answer is "because they can" not because it makes any sense. If the temperature of the roofing was an issue the manufacturer would give a longer warranty for lighter colors. Shingle warranties are based solely on marketing strategies. If you insulate the rafters with fiberglass and vent at the eaves and ridge or insulate with spray foam with no vents, you can leave the air handler and ducts in the attic and save the energy that is now leaking into the attic. If you want your roofing to last longer in a hot sunny climate, select a lighter color or plant shade trees.

How is the exterior of the duct configured? Can you get an electrical line to it? Alternatively, can you get to the duct in the garage and add an in-line blower. Once your hood is in place and operational, you can check the outside for apparent flow rate (with some house windows open just to reduce any MUA choking). If it seems as weak as we might fear, you could consider replacing the cap with a supplemental blower or going with an inline blower. It would have to be wired back to a relay that the hood blower power energizes, or else the hood blower control would have to be upgraded to handle both motors' total power draw. This assumes that the hood uses a standard induction motor with one of the usual variable motor controls. Effectively, the exterior or in-line blower would be lowering the duct internal pressure, thereby compensating somewhat for the pressure losses in the MUA and hood baffles, duct turbulence, etc. The Broan (I think) scheme of using an air flow sensor to turn on an MUA blower won't work in this case for the supplemental blower because once flow is detected, the controlled secondary motor will keep itself on. You might be able to double the achieved flow with a supplemental blower. This should make up for using a duct of half the sectional area needed, but that will depend on both blowers' fan curves. You will possibly end up with adequate performance at the expense of another blower and perhaps a higher than desirable duct air velocity (over 2000 ft/min). In that case, insulating the duct in the garage (if the garage is unheated) will reduce grease collection in the winter. Before using insulation, check for vibration resonances and if needed cover selected duct sections with sound deadening material, such as the lead-filled [my assumption] sticky-sided plastic (maybe it is asphaltic) sheet used for automotive interior soundproofing. There is also the product here, but I have no experience with it. http://www.acoustiproducts.us/ Making the differential MUA house air pressure positive would also help the flow rate, but now house wall leakage outward will contribute to moving moisture into the walls from inside in the winter, a problem unless the house is ultra well sealed.