no high pressure rv2 help!
The thing is cycling on the low pressure switch. You can bypass it for testing, but I would not run it for more than a minute in that condition.
Here's the 72 manual download:
http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download
It's the "72 Plymouth" shop manual
TXV is "thermostatic expansion valve"
I guess I was mistaken, the A series cars evidently don't use an evap pressure regulator.
In the download posted, page 24- on, and again, page 24-31 they say
Onwards through the pages, 24-28, in "charging" they mention RPM, and 24-30, performance tests, they refer you back to that RPM (refer to test 4)
Notice that they speak of watching the sight glass. I've never been big on depending on the sight glass, as on very hot days, it can show foam and still be properly charged, thus leading you to incorrectly add refrigerant. Many newer systems don't even HAVE a sight glass.
I prefer to use SUPERHEAT which is a method by which you insure that the compressor is not being "slugged" by liquid refrigerant. There will be some argument as to just what the proper superheat should be, but I'd say NOT LESS than 10*F and NOT MORE than 25*F
To do that, all you need is the temp. scale on your low pressure gauge, or a pressure-temp chart for R-12, and a good thermometer. Strap a thermometer near the compressor on the suction line and away from engine hot spots as best you can. Insulate the area of the temp. probe, and you usually want the probe to be on the lower 3/4 of the tube, IE about 3-4 oclock or so.
This of course will be after you get the system working enough to finalize the charge, and should be done on a warm day as in the book with doors and windows open. Run the system to get it stable, with a good big fan into the engine. Even better would be a road test, and of course I realize this is difficult if not impossible.
In any case after the system is stable, you read the temp at the suction line and compare it to the temp on the low pressure gauge. The temp difference, 10-20 degrees or so, is your "superheat."
Some of the main things that affect system pressure:
HEAT LOAD. More heat in the passenger compartment, hot day, humidity, sun load, raises evap temp and raises head and suction pressures. Too much refrigerant will raise at least head pressure, and probably suction as well. A TXV (as opposed to an orifice system) and a nice big receiver gives you a little leeway in that dept.
Not enough blower at the evap, plugged/ iced evap, or cold temps lowers it, along with low refrigerant.
Typically, a bad compressor (leaky valves) will give you reduced head but higher than normal suction
AND IS IT POSSIBLE that there is some foreign plug in the system? That is a dust plug over the compressor outlets or something else in the hoses, / fittings?
The thing is cycling on the low pressure switch. You can bypass it for testing, but I would not run it for more than a minute in that condition.
Here's the 72 manual download:
http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download
It's the "72 Plymouth" shop manual
TXV is "thermostatic expansion valve"
I guess I was mistaken, the A series cars evidently don't use an evap pressure regulator.
In the download posted, page 24- on, and again, page 24-31 they say
Onwards through the pages, 24-28, in "charging" they mention RPM, and 24-30, performance tests, they refer you back to that RPM (refer to test 4)
Notice that they speak of watching the sight glass. I've never been big on depending on the sight glass, as on very hot days, it can show foam and still be properly charged, thus leading you to incorrectly add refrigerant. Many newer systems don't even HAVE a sight glass.
I prefer to use SUPERHEAT which is a method by which you insure that the compressor is not being "slugged" by liquid refrigerant. There will be some argument as to just what the proper superheat should be, but I'd say NOT LESS than 10*F and NOT MORE than 25*F
To do that, all you need is the temp. scale on your low pressure gauge, or a pressure-temp chart for R-12, and a good thermometer. Strap a thermometer near the compressor on the suction line and away from engine hot spots as best you can. Insulate the area of the temp. probe, and you usually want the probe to be on the lower 3/4 of the tube, IE about 3-4 oclock or so.
This of course will be after you get the system working enough to finalize the charge, and should be done on a warm day as in the book with doors and windows open. Run the system to get it stable, with a good big fan into the engine. Even better would be a road test, and of course I realize this is difficult if not impossible.
In any case after the system is stable, you read the temp at the suction line and compare it to the temp on the low pressure gauge. The temp difference, 10-20 degrees or so, is your "superheat."
Some of the main things that affect system pressure:
HEAT LOAD. More heat in the passenger compartment, hot day, humidity, sun load, raises evap temp and raises head and suction pressures. Too much refrigerant will raise at least head pressure, and probably suction as well. A TXV (as opposed to an orifice system) and a nice big receiver gives you a little leeway in that dept.
Not enough blower at the evap, plugged/ iced evap, or cold temps lowers it, along with low refrigerant.
Typically, a bad compressor (leaky valves) will give you reduced head but higher than normal suction
AND IS IT POSSIBLE that there is some foreign plug in the system? That is a dust plug over the compressor outlets or something else in the hoses, / fittings?
