Nickelplate Posted August 9, 2022 Author Share Posted August 9, 2022 Larry - Can you post a pic of the high-side switch? I have an FS10 system from a 1990 F250 in Big Blue and it doesn't appear to have that switch in it. Or maybe I'm missing it? Hey, Gary. I figured I would post a pic of mine in case it was different in any way. Link to comment Share on other sites More sharing options...
Nickelplate Posted August 9, 2022 Author Share Posted August 9, 2022 I hope I'm not getting out of sequence here as I have not fully read the thread. I'm just reading a little to wind down from a ten-hour drive. anyway, the systems did not need a high-pressure switch for very many years but then things changed. we retro fit but we are compromising! the fs10 is far more efficient than the fs6 all while using a refrigerant that will happily spike in pressure. that said there is likely an operational reason for the pressure spike. low air flow across the condenser being extremely common. most often from a failing fan clutch. another common issue is a clogged orifice tube from debris coming out of an old condenser/compressor. another is as simple as air in the system (non-condensable) easily introduced into a clean system by the gauges themselves from going from one step to the other. I set up all at once so to maintain the seal between the vac pump, 134a bottle and vehicle. this does require a couple extra hoses. Heya, Mat! Thanks for the info and suggestions. I did definitely check those things. I have my dual electric fans set to turn on 100% when the AC is turned on, so airflow shouldn't be an issue. Orifice tube is new, as are all other components. The oldest thing in the system is the condenser, which is a couple of years old, but with not much use on it. And I did end up using a full manifold gauge set with a filler hose from the r-134a can (I purged the hose using the schrader valve before filling). Adding the high-side pressure switch has definitely alleviated my issue. IF anyone else is going to wire one in, here are the parts I bought. https://www.ebay.com/itm/144634827521 and the switch was labeled "Ford F5TZ-19D594-AA Pressure Switch for A/C Compressor OEM NOS" Remove the two unused leads on the pigtail, then just put the switch in line with the low-side switch on the same lead. Link to comment Share on other sites More sharing options...
mat in tn Posted August 9, 2022 Share Posted August 9, 2022 Heya, Mat! Thanks for the info and suggestions. I did definitely check those things. I have my dual electric fans set to turn on 100% when the AC is turned on, so airflow shouldn't be an issue. Orifice tube is new, as are all other components. The oldest thing in the system is the condenser, which is a couple of years old, but with not much use on it. And I did end up using a full manifold gauge set with a filler hose from the r-134a can (I purged the hose using the schrader valve before filling). Adding the high-side pressure switch has definitely alleviated my issue. IF anyone else is going to wire one in, here are the parts I bought. https://www.ebay.com/itm/144634827521 and the switch was labeled "Ford F5TZ-19D594-AA Pressure Switch for A/C Compressor OEM NOS" Remove the two unused leads on the pigtail, then just put the switch in line with the low-side switch on the same lead. good. certainly, wire this switch in series with the low cycle switch. it becomes a redundant switch but so long as either one can cause protection for their own reasons then it works the same. Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 9, 2022 Share Posted August 9, 2022 I hope I'm not getting out of sequence here as I have not fully read the thread. I'm just reading a little to wind down from a ten-hour drive. anyway, the systems did not need a high-pressure switch for very many years but then things changed. we retro fit but we are compromising! the fs10 is far more efficient than the fs6 all while using a refrigerant that will happily spike in pressure. that said there is likely an operational reason for the pressure spike. low air flow across the condenser being extremely common. most often from a failing fan clutch. another common issue is a clogged orifice tube from debris coming out of an old condenser/compressor. another is as simple as air in the system (non-condensable) easily introduced into a clean system by the gauges themselves from going from one step to the other. I set up all at once so to maintain the seal between the vac pump, 134a bottle and vehicle. this does require a couple extra hoses. Mat, a number of years ago the company my son was working for hosted a seminar on R134 conversions. Part of the requirement the EPA wanted was a "refrigerant containment" system involving replacing the high pressure relief valve with a high pressure shut-off switch. This would, in theory, kill the compressor power and release the clutch. Only problem, like most items, mechanical or electronic, it wasn't fool proof. On the older York or Tecumseh twins and Chrysler V-twins, the clutch bearing is on the crankshaft and a seized bearing results in a continuous compressor run. I personally have had an FS10 on my 1994 Taurus, weld the clutch together due to an internal compressor failure on the highway which it spun long enough to weld itself, then snapped the serpentine belt. I have also had a Chrysler C171 explode the high side discharge hose when the expansion valve stuck shut just as it was starting to balance everything, and this was with R12. Pressure spiked so fast I couldn't even unplug the wires in time. Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 9, 2022 Share Posted August 9, 2022 Hey, Gary. I figured I would post a pic of mine in case it was different in any way. Thanks for the pic. But Big Blue's manifold doesn't have a place for that switch. I have a complete 1990 system on BB, including a brand new manifold. So I'm sure there wasn't one from the factory as the old manifold didn't have it either. Link to comment Share on other sites More sharing options...
Nickelplate Posted August 9, 2022 Author Share Posted August 9, 2022 Thanks for the pic. But Big Blue's manifold doesn't have a place for that switch. I have a complete 1990 system on BB, including a brand new manifold. So I'm sure there wasn't one from the factory as the old manifold didn't have it either. According to my research (looking at the same part for each year on rockauto and seeing when the style changed), ford trucks with a small-block did not get the refrigerant line with the pressure switch port until 1994. Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 9, 2022 Share Posted August 9, 2022 According to my research (looking at the same part for each year on rockauto and seeing when the style changed), ford trucks with a small-block did not get the refrigerant line with the pressure switch port until 1994. Could you check for the 460? Maybe it is the same, which would explain why I don't have it. Link to comment Share on other sites More sharing options...
mat in tn Posted August 9, 2022 Share Posted August 9, 2022 Mat, a number of years ago the company my son was working for hosted a seminar on R134 conversions. Part of the requirement the EPA wanted was a "refrigerant containment" system involving replacing the high pressure relief valve with a high pressure shut-off switch. This would, in theory, kill the compressor power and release the clutch. Only problem, like most items, mechanical or electronic, it wasn't fool proof. On the older York or Tecumseh twins and Chrysler V-twins, the clutch bearing is on the crankshaft and a seized bearing results in a continuous compressor run. I personally have had an FS10 on my 1994 Taurus, weld the clutch together due to an internal compressor failure on the highway which it spun long enough to weld itself, then snapped the serpentine belt. I have also had a Chrysler C171 explode the high side discharge hose when the expansion valve stuck shut just as it was starting to balance everything, and this was with R12. Pressure spiked so fast I couldn't even unplug the wires in time. everything works perfectly when working perfectly. then life happens! Link to comment Share on other sites More sharing options...
Nickelplate Posted August 9, 2022 Author Share Posted August 9, 2022 Could you check for the 460? Maybe it is the same, which would explain why I don't have it. Yep! Looks like it changed after 93 for the 460 too. 1994 1993 Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 9, 2022 Share Posted August 9, 2022 Yep! Looks like it changed after 93 for the 460 too. 1994 1993 Yep! That '93 manifold is exactly what BB's looks like. Thanks! Link to comment Share on other sites More sharing options...
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