| Author | Message | ||
     Randy Roberson Grand Master Username: wascator Post Number: 424 Registered: 5-2009 |
Gents, I got the R134A refrigerant topped up to the approximate amount of 34 ounces as recommended in the Factory bulletin, available on this Forum. The compressor is very smooth and quiet; the suction lines sweat, condensate drips down under yonder. The temperature at the round outlets, traveling at 50 MPH, at an ambient of 80F, is 60 degrees F. Approximately the same performance with the Car stationary in my drive, with a good fan directed toward the Majestic Grille. Frankly I was hoping for outlet temps to be colder. Here in the South in summertime this level of performance would be complained about by the average motorist: it would not really keep a vehicle comfortable most of the time, even with the fan on high constantly. Any comments? | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1363 Registered: 6-2009 |
Randy, What is the position of your temperature dials? Oops, failed to notice this is about your 1970. I would be surprised if you cannot achieve greater than a 20-degree temperature drop from ambient. I don't know how similar the one series cars are to the two series as far as taking the air down to as low a temperature as can be achieved for dehumidification and then is heated to modulate the final temperature. If that principle is used you might want to check what's going on at your heater tap and whether it cuts off flow completely for maximum cooling at the outset. Brian | ||
| Randy Roberson Grand Master Username: wascator Post Number: 425 Registered: 5-2009 |
The Shadow I system is much more simple than the Shadow II system: just a basic system, really. it is possible the heater valve could leak and add heat, and I haven't found this to be the case but I will look more closely this weekend. I had a similar experience with an S-Class Mercedes-Benz: the unit just would not get as cold with R134A. Some blamed it on condenser efficiency, but it seemed to me that, if that were the case, performance might be weaker at idle, but at 60 MPH there is a lot of air though that condenser. Plus, I turned the water hose on it and it made no noticeable difference in outlet temp. Seems to me also that, if the refrigerant liquefies in the condenser, and the pressure in the evaporator is right, it should be cold. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1365 Registered: 6-2009 |
Randy, All I can tell you is that SRH33576 is running R134a and it can crank out air that's cold enough to freeze off your {insert appendage of choice here}. Not that you don't already suspect this, but something must be "off." Brian | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 750 Registered: 5-2012 |
Randy I'm in Florida, so the ambient temperatures are similar to yours in Louisiana. My 1974 SY1 (SRX18501) copes very well. I have never measured the temp at the outlet, but it feels ice cold and keeps the car cool. It may be my 74 has seen some upgrades. Here's a picture of the compressor.  Is yours the same? One problem I have is there was obviously some work carried out on my aircon by a previous owner. The flexible pipe from the compressor is too short, so not only does it snag against the oil filler cap, it also pulls tight against the front suspension turret, which means the sound of the compressor can be heard inside the car. It is quite obtrusive and annoying. yet another little job for me sometime in the future. Geoff | ||
| Randy Roberson Grand Master Username: wascator Post Number: 426 Registered: 5-2009 |
Geoff, mine is like yours. My Car still has the suction throttling valve. As far as I can tell it works and doesn't leak. Brian, I am also working on the '77 Wraith II's air, and it should I hope have similar performance to yours when I get it going. Do you still have the POV or is it converted to cycle the compressor on-off? I sent my POV to Florida to have it overhauled and tested. My Shadow I still has the suction throttling valve. It doesn't leak refrigerant, however I don't know if it could have failed somehow and be causing the higher than desired temperature. I know the positioner motor works as intended. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1366 Registered: 6-2009 |
Randy, I believe I have the POV since the compressor never cycles. In fact, I had never had a car where the compressor didn't cycle, and that worried me quite a bit when I discovered this driving cross country in 2007. My partner and I suffered some awfully hot days because I was afraid to use the A/C until "I find out what went wrong." It's part of the charm. I will add, though, that when I thought I was having an issue with my heater tap I put a cut-off valve in the line to the heater core. If I turn this off during the summer months I can get meat-locker like temperatures in the car (without the system freezing up - but when you live in beautiful humid Virginia [yes, I know, Louisiana and Florida are both far worse] that's not a surprise). Brian | ||
| Robert Noel Reddington Frequent User Username: bob_uk Post Number: 82 Registered: 5-2015 |
My 1974 car. The temp from the eyeball vents is low enough to hurt my left hand. Right hand drive of course. | ||
| Randy Roberson Grand Master Username: wascator Post Number: 427 Registered: 5-2009 |
That's as it should be. I am going to investigate if the suction throttling valve is adjustable. I might be able to lower the suction pressure and thereby the temperature. | ||
| Robert Noel Reddington Frequent User Username: bob_uk Post Number: 83 Registered: 5-2015 |
My car still has the suction throttling valve. In the workshop manual is how to set the valve. Basically the servo has 4 positions. These are checked by fitting gauge to the low pressure port. There is a bit on the valve stem which screws in and out. | ||
| Randy Roberson Grand Master Username: wascator Post Number: 429 Registered: 5-2009 |
Great! I thought that would be the case. Checking... | ||
| John Kilkenny Prolific User Username: john_kilkenny Post Number: 204 Registered: 6-2005 |
My 1966 Shadow 1 has the big Frigidaire compressor.After troublesome leaking of the suction throttling valve it was replaced with a temperature switch at the evaporator to control the compressor clutch. When using R12 the system was very efficient with ice forming on the pipes. However after changing to R134A it was never as good and struggled on very hot days. At the suggestion of a local refrigeration mechanic I changed the refrigerant to MINUS 30(a blend of R600A and R290 natural gas refrigerants) which though not as good as R12 is quite cold enough. An interesting article on hydrocarbon refrigerants is here http://www.airchill.net.au/auto-motive-air-conditioning-gases.html | ||
| Randy Roberson Grand Master Username: wascator Post Number: 431 Registered: 5-2009 |
This afternoon I bought insulation and covered the pipe downstream of the suction throttling valve. It has about 6 inches which is exposed and is within a few inches of the B-bank exhaust manifold. That had to be picking up considerable heat before the liquid even got to the evaporator coil. I looked at the suction throttling valve and located the round nut which is the pressure adjustment. it requires a special pin wrench which of course I do not have. Also I noticed this: the threaded bore in the valve casting in which the nut is positioned seems to be distorted. It is oval on the end, and it appears the cast arm which supports the fulcrum has pulled on the casting and caused the distortion. Has anyone noticed this? I might be able to turn the nut some with the proper wrench, but the distortion may prevent it and so I may need a good suction throttling valve. | ||
| Randy Roberson Grand Master Username: wascator Post Number: 433 Registered: 5-2009 |
After thought I have repented of insulating this pipe: this is flow from the evaporator, and it needs to be bare to absorb heat. this prevents liquid refrigerant from entering the compressor. So, off comes the insulation. I know that the key is adjusting the STV; I have ordered the replacement, upgraded upper part from Albers', along with a repair kit. | ||
| Robert Noel Reddington Prolific User Username: bob_uk Post Number: 103 Registered: 5-2015 |
Normally the stv is disabled and gutted. Instead a sensor on the evaporator outlet is fitted. This via a relay works the comp clutch. However the stv system does work. | ||
| Randy Roberson Grand Master Username: wascator Post Number: 450 Registered: 5-2009 |
I got my STV out and dismantled it this afternoon. It is an impressive part: very robustly built except for the obviously weak upper housing which is warped by years of pull by the springs. Anyway, I ordered the improved aftermarket housing and a repair kit from a US vendor. I dismantled the valve and cleaned it up; it was in good condition in side, best I could tell. Alas! I found that when I tried to assemble the valve, the new part was not made accurately enough: the pivot support arm is not perpendicular to the centerline of the valve, and it binds up rather than move smoothly. I'll contact the vendor Monday, but it is annoying that the part is not right, especially considering the $250 it cost. Oh, well: I think it will allow me to adjust the evaporator temperature to get colder output from Her refrigeration system. It will be worth it eventually. | ||
| Randy Roberson Grand Master Username: wascator Post Number: 480 Registered: 5-2009 |
I got the STV installed, the system vacuumed and recharged, and had about the same situation as before: circa 60 to 65 F out the vents. I adjusted the STV to lower the pressure (i.e. counterclockwise) a few turns. It was controlling the suction pressure at about 35 PSI. I got tired and rigged down until later. I did turn the adjustment out another couple of turns, which should lower the suction pressure more. It might be that we need a slightly lighter spring, to get the evaporator pressure and temperature down. If the suction pressure is correct, we should see the corresponding temperature. |
