A/C Refresh – Making a Meat Locker
Please subscribe to the YouTube channel if you have not already. Also, find us on Facebook and Instagram as Purist Motorsports. Don’t forget to like and share our content.
Author: Michael Yount
Set about to recharge the A/C on the Corolla. It was working, but only “coolish” temps. It seemed to hold pressure fine. Weirdness – only 1 R134 fitting on the low side of the compressor with a “high” (red) cap on it. Based on that and the way it’s behaving, I think there’s a chance that it never had a vacuum pulled; damned likely that it never had a gauge set on it. Looks like someone might have put just put one fitting on and then tried adding the freon.
Anyhow, picked up a fitting set, removed the Schraeder on the high side and installed without incident.
Pulled a vacuum down to 29″ (only took about 10 minutes – a good sign) and left it overnight – still 29″ in the morning. Quickly replaced filter/drier, added 1oz PAG to replace that left in the old filter/drier, then pulled vacuum for an hour (30″) and charged using the gauges as a go by.
Didn’t use a scale because I had no weight spec for the bastard system in the car – I ‘think’ it came out of an ’81 Corolla – but not certain. Had it been the dealer-installed Nippondenso unit back in ’73 it would have had the big York 2-cylinder compressor – and this has a nice, compact Denso rotary compressor. Smooth and quiet. Anyhow, I got to 20-25 psig suction, 200 psig discharge and around 40F vent temps (inside of the car glass was fogging on a humid morning – daddy happy!). I’m guessing 15-17 ozs was all it took. Little car sat and idled at 1100 rpm for about 50 minutes – never missed a beat, temps sat right on 200-205F. Maybe my makeshift cardboard ducting and box fans helped — but the DCC-controlled cooling fan was doing its work just fine.
Now, when I went for a ride – I damn near turned the inside of the car into a freezer. I left the temp gauge in place. With more revs and more air moving across the condenser I saw 21F on the temp gauge within 5 minutes of leaving the house…. I AM NOT KIDDING. The compressor wasn’t cycling off. Didn’t get to play with the temp setting as much as I’d like — I’m guessing the expansion valve control isn’t working like it should. And it’s an old system with no high/low pressure switch. It will freeze your ass out of the car. 1973. Who’d’a thunk? Of course, those temps are a problem as it would have pretty quickly turned the evaporator coil into a block of ice.
For the time being, I’m going to put a switch in the compressor clutch wire – so I can manually cycle the compressor from inside the car. That’ll let me attend cruise-ins and such in cool comfort. Meanwhile looking to see if I can find replacement expansion valve and add a high/low switch. There’s a threaded spot for a switch on the filter/drier. I’ll have to pull the system down again to add it — but now that I know what I’m doing with it — a piece of cake + $15 of 134. The other alternative is to spend $300-400 and buy a completely new under-dash unit (that’s what’s in the car) with a contemporary control system. I think the compressor and evaporator are working fine. 21F temps and all…. Charge must be close – get over full or under full and warm air shows up. This is anything but warm. So I’m calling it a win – that needs a bit more adjustment.