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Don't get ahead of yourself! (long) Posted by JerseySaab [Email]  (#666) [Profile/Gallery]
(more from JerseySaab) on Tue, 26 May 2015 10:46:35
In Reply to: Which port is low port?, Haskell60 [Profile/Gallery]
, Tue, 26 May 2015 08:31:26
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There are a number of issues here.
You really need to get a gauge set connected and see what the pressure is in the system. For this purpose the low-side gauge that comes on some recharge kits may do the trick, but a full gauge set really should be used for AC work. (Harbor Freight sells one that works OK and is not too expensive, though it is set up for R134a connectors. You would need adapters if you still have the original R12 ports, or buy a gauge set with R12 hoses.)
Rest pressure varies depending on temperature, refrigerant, and state of charge, but I think the pressure switch on the C900 will disable the AC system if it falls below maybe 15 pounds or so.
If there is no pressure at all in the system then you may well have a major leak to fix, and your system may have been exposed to atmosphere for a while meaning you need a new drier and need to evacuate air and moisture with a vacuum pump. On the other hand, if there is some residual pressure you probably just have a slow leak and a recharge may get it to work for a while.
An important issue is whether the system already been converted to either R134a or an alternative refrigerant. Given your description of the caps it sounds like it may have R134a with conversion fittings, blue would normally be the low side where refrigerant is charged in. (There may also be an "S" or "L" on the compressor itself near that fitting.) But you really need to know what refrigerant is in use, it's possible that someone filled it with, say, envirosafe and installed R134 fittings. Or you may have the original R12 fittings with color-coded caps on them.
Then of course there is also the possibility that the safety pressure switch is bad. You may also find a temperature switch in the upper radiator hose and that also might be defective. (It switches the AC system off if the engine starts to overheat.) Other possible electrical issues would include the A/C relay, the antifrost temperature switch, the diode inline with the compressor clutch (it prevents spikes from backfeeding into the circuitry), the compressor clutch itself, and the signal from the computer that engages the AC.
So you really need to do more diagnosis before taking action. It's not rocket science, the C900 has a very basic AC system, but if you do the wrong thing you may do more harm than good.
Also if you find that you do have a leak I would not use sealer to "fix" it. AC sealers work by hardening on exposure to moisture in the atmosphere. Guess what happens if you have to open up the system later to work on it? (A friend of mine found out the hard way a couple of years ago on his Toyota!)
There are a number of ways to find leaks. You can inject dye into the system and use a black light to find traces. You can use soap bubbles at connectors. For R12 or R134 an electronic detector works well and there are some fairly inexpensive ones out there. (These don't work though with hydrocarbon-based refrigerants such as Envirosafe or Duracool, at least not unless you spend some major $$$.)
ALWAYS WEAR EYE PROTECTION when working on an AC system, preferably the type of safety goggles that will keep liquid out!
->Posting last edited on Tue, 26 May 2015 11:23:59.
, Tue, 26 May 2015 07:28:37, Tue, 26 May 2015 07:35:28, Wed, 27 May 2015 13:10:12
, Wed, 27 May 2015 13:48:55, Thu, 28 May 2015 11:31:03, Wed, 27 May 2015 14:15:35, Tue, 26 May 2015 08:31:26, Tue, 26 May 2015 10:46:35 <-- Viewing This Message, Tue, 26 May 2015 11:33:09
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