Re: Random questions about 51-56's, Ultramatics and A/C

Posted by HH56 On 2018/3/9 16:37:22

Believe the 55-6 AC was engineered by Packard in house and was really an accomplishment when you consider they did it in a way so as not to require any major changes to the car. Other thru dash systems at the time were comparatively bulky and new firewall stampings would most likely have been needed had they adapted the Harrison or even the Nash system. All Packard had to do to the stock firewall and dash was cut 4 relatively small holes in the existing sheetmetal and bolt the system in. Dealers could install a system in the field. Of course you can forget about accessing anything easily when working under the dash when AC was in the car. For anyone curious on the AC unit details there is a dealer field install manual on site.https://www.packardinfo.com/xoops/html/downloads/55-56ACInstall.pdf

The system worked very well. When AC was turned on the compressor energized and stayed on. The only operator adjustment was the blower speed. Temp regulation was fixed using the hot gas bypass method controlled by the modulator valve. The modulator valve was adjustable but not by the operator and was usually set to keep the evaporator in a range right around 40 degrees. It is a huge evaporator coil and ice cold air would come from the dash top vents and could also come out the floor opening if the heater door was opened. Heated air could also come out the dash vents in winter if desired so in effect it was a true bi-level system. On high there was a decent amount of air flow from the dash vents that does skim the roof line and reach the back seats -- although by the time it gets there it is obviously more of a small disturbance than a real feeling of air blowing. The vent angle can raise or lower slightly to somewhat direct air up/down and there was a lever operated set of louvers in the vents to direct side to side. When it got too cold you could turn the blower speed down and you could even start the heater and have it run at the same time mixing hot and cold air if you wanted more temp variation.

Return air uses the Left side knee air vent. The vent control knob is modified so the air flapper on the left can then go three positions like the right heater side. By varying the knob you can close or admit outside air to the AC system as well as recirculate inside air or not.