Air conditioning - pressure switch bad? Reply #15 – April 24, 2009, 10:00:24 PM What's the cylinder near the compressor? Just a ler? Why the foam? The replacement discharge lines don't have it...I also like the $100 97/98 condenser price on rockauto, not too bad. Quote Selected
Air conditioning - pressure switch bad? Reply #16 – June 28, 2009, 12:36:48 AM Okay, so I put the new condenser in, along with a new acspoogeulator/hose and liquid line. The compressor still gets to a point where it won't turn on anymore. It only hit ~100 psi on the high side, around 30 on the low before it quit spinning when I had the switch jumped. The compressor just comes to a screeching halt at this point and rejumping it makes it only turn on for a split second before halting again. Now it won't even engage. I hope the compressor isn't bad as it has next to no use on it - it's not a cheap autozone replacement either. Quote Selected
Air conditioning - pressure switch bad? Reply #17 – June 28, 2009, 01:44:03 AM Perhaps a weak clutch? One would think it would engage either way as long as the clutch/bearing/coil are fine. Quote Selected
Air conditioning - pressure switch bad? Reply #18 – June 29, 2009, 09:22:44 AM Have you verified that 12V is coming to the clutch? If so, and the clutch isn't engaging, you have a bad clutch or your air gap is too big. Quote Selected
Air conditioning - pressure switch bad? Reply #19 – June 29, 2009, 10:37:44 PM 12v yes - the clutch tried to engage but stops pretty quickly and won't turn anymore. I can turn the inner area of the pulley by hand easily. I'm going to just install a replacement and then take this one apart to see what is wrong with it. I've got spare parts of everything else, why not an a/c compressor also?! :hick: Quote Selected
Air conditioning - pressure switch bad? Reply #20 – June 30, 2009, 10:45:18 PM Okay, so I tested some things. Jumping the compressor from the battery works all the time. This draws 3 amps. When jumping the positive from the pressure plug and grounding to the battery, the current draw is only 100mA (13.6v - doesn't drop with the compressor connected or not). WHAT would cause my amperage to be so low?! I tried replacing the 20A fuse thinking perhaps it was old and tired but no go. Must I start testing the wire from the HVAC controls?I could hack it together with a relay but who knows how long that would last.Edit:I didn't do FULL tests earlier. I found in the end that jumping from the pressure switch straight to the clutch coil draws exactly 3A and engages the clutch. I can't seem to pinpoint some wiring diagram for this - does anyone have one? The wire is good from the pressure switch to the wire harness and the wire harness to the compressor (tested with poking a hole in the insulation right outside the harness). Quote Selected
Air conditioning - pressure switch bad? Reply #21 – June 30, 2009, 11:40:16 PM Is one of the relays on the passenger side shock tower the WOT cutoff? This could perhaps be the issue... Quote Selected
Air conditioning - pressure switch bad? Reply #22 – July 01, 2009, 12:10:02 AM problem solved - bad wot relay. Quote Selected
Air conditioning - pressure switch bad? Reply #23 – July 02, 2009, 01:13:26 AM New problem! The system holds 29" of vacuum for hours but whenever I get up to around 170psi dynamic on the high side (tried two different charges with replacing all the orings again between the two), all of a sudden it goes downhill and my gauges start reading lower and lower. I was at 80psi static until I went to add more than 24oz - the third can dropped it to 70psi static and the liquid line gets barely cold and the condenser stays cool. It holds pressure though. High side is up to ~180psi before the pressure switch turns the compressor off. It was cooler at 140psi high when it was at a static pressure of 80psi. What would be causing this?! It makes no sense!Edit:This is with an ambient of ~90 degrees Quote Selected
Air conditioning - pressure switch bad? Reply #24 – July 02, 2009, 06:12:58 AM 180psi on the high side sounds a bit low... at what low pressure is the compressor cycling? And, is the compressor cycling quickly, or slowly? If I remember correctly, on a 90* day on high fan you should be seeing high-side readings of around 250psi and your cycle switch should cut the compressor right around 32psi low-side. Shiny Side Up!Bill Quote Selected
Air conditioning - pressure switch bad? Reply #25 – July 02, 2009, 08:56:56 AM I've currently got it set to cycle off at 22psi. It takes about 30-40 seconds from when it's on for it to turn back off. It comes on at ~50psi low and off at 22. I had a hot condenser at 150psi high but it's cool at 180psi, along with the liquid line being warm. It's like it just stopped cooling completely. Quote Selected
Air conditioning - pressure switch bad? Reply #26 – July 02, 2009, 09:11:29 AM Quote from: Seek;280572I've currently got it set to cycle off at 22psi. It takes about 30-40 seconds from when it's off for it to come back on at ~50psi low and off at 22. I had a hot condenser at 150psi high but it's cool at 180psi, along with the liquid line being warm. It's like it just stopped cooling completely.22psi is way too low, the evaporator will freeze up... maybe this is what happened? With 134A you may be able to go as low as 28psi, but anything lower will put your evaporator temps below 32* and cause the formation of ice across it. This will cause the a/c to blow warm air, and may cause the inverse pressures you experienced as the system will no longer be absorbing any heat from the evaporator. No heat means no pressure, and your pressure of 22psi roughly equates to an evaporator temperature of 25*F.Shiny Side Up!Bill Quote Selected
Air conditioning - pressure switch bad? Reply #27 – July 02, 2009, 09:22:54 AM Here is a chart I found: http://www.csgnetwork.com/r134apresstempconv.htmlShiny Side Up!Bill Quote Selected
Air conditioning - pressure switch bad? Reply #28 – July 02, 2009, 11:04:45 AM Interesting - so the information I've found from numerous sources telling me to adjust the screw in the pressure switch to 21-22psi low (from 25 stock for r12) are wrong. Most information on the net is taken from the same original source anyways. To what extent should the r12 parts (with proper desiccant acspoogeulator) work with r134 refrigerant? I think my liquid line's got a standard orifice tube that lets too much refrigerant by, preventing proper 240-250psi high side pressures before it leaks past to the low side.I will give this a try. Quote Selected
Air conditioning - pressure switch bad? Reply #29 – July 02, 2009, 02:29:58 PM I have worked only on 4 AC systems (2.5 retrofits and 2 "top offs"). I have been learning alot since moving to San Antonio however (its 102*F outside right now.....kill me).I did find this chart: http://www.hvacmechanic.com/refrigerants/ptcharts.htmIf you look up R12 at 25 psi (yellow), that equates to 26*F. If you follow 26*F over to R134a (light blue) it occurs at about 23 psi. So what seek said, makes sense to me. An equivalent pressure for R12@26*F 25 psi equates to R134a@26*F 23 psi.I'm not telling you to do it, I can understand why someone would tell you to adjust the switch. If you left it at 25 the coldest R134a would get would be about 29* so you would loose about 3* of cooling capacity. I assume the system is designed to work with a minimum of some cfms of airflow across it (hence the R12 temperature being lower than 32*c). I wonder what freon temp ice begins to form. Quote Selected
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