[DeTomaso] A/C final chapter

[Tom Shinrock]

I thought I give a final update on my A/C project.  

It's been almost a month since I reported that I had received the wrong size condenser from Classic.  I called them up and told them I had received the smaller condenser for an early Pantera and needed the larger condenser for my' 73 car.  They were very good to work with and said they would send out the larger unit and include a prepaid shipping label to send the smaller one back.  After two weeks of not receiving the new condenser I gave them a call.  They looked into it and reported back that UPS had apparently lost the shipment (how does that happen?) and they would send out a second unit and a shipping label, which I received in four days.

I had the new condenser installed and the system recharged.  To summarize my system I'm running R12 refrigerant with the sanden SD-508 rotary compressor, stock evaporator valve, stock hoses with flare fittings, four row rear mounted condenser with stock fan/shroud, and new drier with a high pressure cut out switch.  I have heater hose shut off valves and, based on advise I have received by many, I leave the trunk tub in the car now (instead of sitting in its 26 year old spot in the basement).

It looked like I would get some good conditions to test the system since the forecast was for several days in the 90s following the installation.  However, the weatherman got it wrong (again) and we had overcast conditions so the temps only got into the mid 80s. The first test was on a day that was overcast with a temperature of 84 deg (can't remember what the humidity was but it was on the high side).  The heater hose shut off valves were closed and the trunk tub was in the car.  I took the car out and was seeing vent temps as low as 30 deg driving in town.   I went out to a highway and saw 36 deg vent air at 55 - 60 mph.  I then went out to the interstate and saw 39 - 40 degree air at 75 - 80 mph.  I drove about 40 miles during the test and the vent air never got above 40 deg air.  It was so cool that I only ran the fan on low.

The second test was similar conditions (temp was 85 with overcast conditions and high humidity).   Drove 40 miles on interstate and saw the same results with the fan on low.   I figured if I could get 40 deg air at interstate speeds I would be a happy camper.

Took the car to a show yesterday.  Conditions were clear skies and 86 deg with lower humidity.   Drove west to the show around mid afternoon with the sun shining through the windshield.  The coolest air I could get out of the vents was 50 deg.  WTF?  The temps were very similar to the prior tests when I consistently saw 40 deg air so I was disappointed and was seeing more $ signs thinking I had a leak somewhere.  With the fan on high it still felt cool but was not cold.  Left the show a couple of hours later with outside temps around 87 deg.  Driving back home the early evening sun was at my back and I was again seeing 39 - 40 degree air out of the vent.  This made me feel a little better and I can only surmise that the system gets taxed by the added heat load through the windshield since that was the major difference from the drive to the show and the prior tests.  As I understand it, the A/C absorbs heat so I assume there is more heat than the system can keep up with.

For comparison, I took a vent air reading from my '86 Porsche 944T which has one of the coldest A/C systems I owned.  It originally was an R12 system but I replaced the compressor/drier and converted to R134 four years ago.   I saw 40 deg air at the vents but it has 300% more vent area and a four speed fan which moves a lot of air.  I usually only run the fan on low and sometimes have to move the thermostat up a little to stay comfortable.  With the Pantera only having two vents (one of which is greatly misaligned from the hole in the air box)  and two fan speeds the A/C performance is compromised even though it puts out the same or cooler air.

So it appears I can't achieve the "Pantera nirvana" that Mike Dailey was able to get to (temps in the mid 30s at speed) but at least I think I have decent A/C.  I think I could be comfortable on long drives in the summer heat but it remains to be seen if the A/C can make the car bearable in the kind of heat I saw on my drive back and forth to Phoenix.  Fortunately we don't see that kind of heat very much in Iowa.

Happy 4th to everyone.

Tom
#5186