We had under dash in our Pontiac wagon when I was little, it would blow ice pellets if it was humid. It was a 9 passenger Safari, setting in the back was still hot!
When I talk to people who have done in dash air & underdash air most say the old underdash units work better.
I had an underdash unit and condensor from a full size 66 Mercury in my 65 F100.. would freeze you out I am going to install a unit from the rear of a van that has a/c and heat combined hidden under the dash It has the a/c and heating pointing towards the passenger side tucked up close to the rear of the unit 3 speeds and blows strong, has 4 round outlets in the front, 2 of them will go to the windshield vents on top of the dash Ricky.
Interesting observation. For sure, most under dash units from what I’ve seen are physically smaller. Smaller evaporator coil and smaller blower. The advantage of the under dash units is that the air exiting is directly off the coil, whereas in dash units will have ducting with the associated outlet vents. The cooled air travelling though this ducting will undoubtedly pick up heat along the way, so it will likely be a bit warmer than tbe air from an under dash unit, and folks will then says it works better, but overall cooling capacity is dictated by evaporator coil and blower size assuming the rest of the AC system components are sized accordingly.
All closed cars are horrible for heat gain, compared even to a badly-designed building. New cars are worse: their roofs are postage stamps bounded by windows, which are huge despite being glued on over odd-shaped porthole openings, and moreover far closer to horizontal on aggregate than even a lot of '50s stuff. Earlier cars with smaller and more vertical windows offer better insulation options. I've seen what happens with heat gain. I've had enough people wanting me to run thermal calcs on trendy neomodernist Barcelona-Pavilion-by-the-Sea and expecting me to magic the heat gain within the limits. I don't need to enter a single dimension to see that it literally won't have a snowball's hope in Cape Town in February, never mind hell. I run the calcs to be able to tell them whether they need to change 80% of the glass to masonry, or just 70%. If the underdash units work better, could it be because the exposed units themselves get cold, and act as radiant cooling?
On another AC auto forum guy who worked for John Mitchell, makes the Mark IV. He said the original allegro was rated at 20,000 btu and the repop isn’t as big it would be closer to their monitor version back in the day. I think what I hear from people is cooling is lost through duct work on after market in dash units or cable controls are often finicky, set them once per season. One of my mechanic friends put a va in his car and the electric controller was bad out of the box.
We made some crude (all steel box) evap units when I worked for Mobile Climate control similar to those pictured above, but they were mostly used in ambulances, limos, small construction and forestry equipment. The automotive AC aftermarket was not our focus. When we moved up to designing and building larger bus AC systems, I quickly realized that the capacity claims of our competitors were exaggerated by up to 25% based on our software program and actual testing. The same can be said for the smaller units. It’s all a sales gimmick to gain market share. I doubt any of the units above are close to 20,000 BTU/hr actual capacity. Probably closer to 12,000 - 15,000 BTU/hr.
Another thing to add to Ziggsters'& Nedds' comments; is that in the 50's/60's, underdash units besides having a very short exit length(not running thru the dash picking up all various components' heat), a lot of the coolant valves would actually shut off the coolant flow. So *one* reason htr cores would partially plug up inside w/sediment. While I'm not sure just when the constant-flow htr-core flow valves came out & were used everywhere - & I'm too lazy to search on the web - I can tell you the a/c picks up a *lot* of heat from them. In the bus-level systems, the heat was rated at least twice the capacity of the a/c. So, a seeping coolant valve gasket would negate any useful a/c, esp @ ~ 90*F+. & it doesn't take much... The valves for the main core(s) would actually shut the flow off entirely, but the ones used for the drivers were exactly like standard automotive types, allowing constant flow(no matter how they were adjusted). So when the designers decided to be "trick" & run the fresh air thru the htr core, like they have for decades, you get the extra heat added to the ambient temps as a free bonus. Fun stuff in ~95*F w/80%+ humidity. Unless you put a hard-shut-off-valve inline w/the htr core, it will *always* put out heat. Look inside the std htr valve - it's a barrel valve & also has a long slot that allows flow thru 100% of the time, at what, 15+psi & ~200*F? So you get to cool that, also. Now, if you run the a/c simultaneously w/the defrost, well, that's a good useful idea - but then, that's planned for. Point being, is you can use a smaller evap core & get very good cooling. But the details can get you. Marcus...
Hey, Budget; AFAIK, it's still available out of Mexico, in 30lb containers only. A "loophole" when R-12 was "phased-out" in favor of the ozone-saving R-134, & now even newer blends(that have a lot of *cough, cough, hack! troubles/expenses* - uhm, I mean: benefits). Apparently, doing it this way, all the ozone was saved, & DuPonts' (among others) market stranglehold profits were never a factor. (Ignore the sarchasm). [Misspelled on purpose.]. From which particular supplier, I don't know, as I haven't searched. Also, iirc, when R-134 1st came out, you didn't need a License to get the small 1lb cans for "topping off" your car/truck. Last I heard, from a friend a couple years ago, Licenses now needed, although I haven't tried to buy it. Marcus...
Just bought some 134 the other day and no problem in getting it but the price has doubled since I last bought it.
Thanks, I'm in mn, don't need any for now. When I was doing hvac, was for a bus co, & I had nothing to do w/the purchasing, other than to tell them what I needed. & keeping track of what I used, into what. Now I'm thinking maybe I should have some on the shelf... , it's slightly less hassle(for now) than using propane. Marcus...
I’ve heard this with older evaporators. I don’t recognize yours what brand? What size condenser do you have?
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