Allis-Chalmers 7020 Tractor Air Conditioning Overhaul, Part 2 скачать в хорошем качестве

Allis-Chalmers 7020 Tractor Air Conditioning Overhaul, Part 2

Part two, where things are going a lot better. It's possible the system is still a little undercharged. People who have reworked the A/C system on other Allis-Chalmers 7020 tractors have reported varying amounts of refrigerant providing satisfactory performance -- from as little as two and a half pounds to slightly over three. I'm sure someone will point out that there wasn't a true 20 degree temperature difference between supply and return. You are partially correct. The cab HVAC system does pull outside air in as it operates. That's what the vent slats in the top of the cab are for. In any case, I want to see what the system does in normal use before I make any further adjustments to the refrigerant charge. Things may look very different in the beating hot sun with the side panels on, pulling an implement and the only real airflow coming from the engine cooling fan. The head (high side) pressure seemed a bit high to me. I have read that older air conditioned tractors and combine harvesters often do operate with higher head pressures than those considered "normal". I have also learned from the comments made on the previous video about this project that TXVs in MVAC systems are seemingly much more common than I would have expected. The new TXV from AP Air is rated for use with both R-12 and R-134a refrigerants according to its packaging. 0:00 - Welcome Back 0:18 - Old thermostatic expansion valve (TXV) removed and inspected. 2:40 - High quality vacuum cleaner! 3:02 - Messed up pipe threads on the evaporator suction line. 4:38 - Ouch (also the name of a hit song by Clint Black ;-) ) 4:43 - Close up look at the damaged threads. 5:31 - Tap and die set. (By the way, it turns out to actually be kind of hard to find a 7/8" die.) 6:05 - Trying to save the damaged threads. 6:36 - Did we succeed? 7:15 - New TXV Installation 7:57 - Is the new TXV bad? 8:54 - AP Air says "charge it and see"! 9:31 - 1700 micron vacuum. (Not great, but it would hold and passed a decay test.) 10:37 - Wrapping the suction line and TXV sensing element with insulation. 11:08 - Not pretty, but it is insulated. 11:30 - New refrigerant scale. 11:47 - Bosch customer service "diatribe" (your word for the day). 12:18 - PLONK! 13:10 - Refrigerant charging, attempt number two. 15:33 - First sight glass check with two pounds of refrigerant. (Interior blower fan speed set to maximum.) 15:42 - First in cab A/C air output vent temperature and humidity reading. (High humidity at the air outlet is expected. The humidity drops as the air blends with that already in the conditioned space.) 15:53 - 2.5 pounds of refrigerant. 16:08 - Outdoor air temperature and humidity. 16:13 - Second in cab A/C air output vent temperature and humidity reading. 16:23 - Second sight glass check, 2.5 pounds of refrigerant. 16:33 - Manifold gauge check. 16:43 - ~2.75 pounds of refrigerant, which is where I stopped charging. 16:51 - Second manifold gauge check. 16:56 - Second outdoor air temperature and humidity check. 17:04 - Third in cab A/C air output vent temperature and humidity reading. 17:14 - Third sight glass check, 2.75 pounds of refrigerant. 17:25 - Thermostatic expansion valve (TXV) and evaporator line temperature checks. 18:45 - In cab weather report! 19:38 - Fourth sight glass check. 19:52 - Another in-cab temperature check, taken away from the supply air vents. 20:15 - Watching the system run. 20:39 - Gauges off, protective caps installed. 21:04 - Goofing around. 21:25 - Putting the tractor away for the night. 22:11 - The condensate water drain is working. 22:31 - Closing.