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Technical Discussion Forum For the discussion of technical questions about Professional Cars and their repair and maintenance. Posting in this forum is limited to PCS Members and / or Site Supporters. We encourage all website users to become members of the Professional Car Society and / or become Site Supporter. |
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#1
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My ambulance has 2 switches for the ac, one turns on the fans and the other Im not sure beacuse nothing happens. Its a 76 S&S Professional. Does anyone have a basic layout on how the rear ac works? Is there a compressor of some sort in the unit?
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#2
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The front ac has to be on. The unit is just anothef evaporater. So if the ac in the car works and the fan comes on you should have ac in the rear unless someone removed the lines.
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#3
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So speaking of S&S A/C the compressor doesn’t kick on unless you jump it in my 74. Is there a relay or something that might not be working. It does have that dial thermostat in the front...
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Current owned: 1974 Sayers and Scovill Professional Ambulance Previously owned: 1973 Miller Meteor Lifeliner Ambulance Future ownership: 1971-1973 Wayne Sentinel Suburban Ambulance |
#4
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Try recharging it.the low pressure switch will not let the compressor come on when you jump it ther is enough pressure t o keep it closed.
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drop in for coffee anytime |
#5
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Ok did a leak detection and none noted. The system was charged as doing the change from R12 to current standard juice.
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Current owned: 1974 Sayers and Scovill Professional Ambulance Previously owned: 1973 Miller Meteor Lifeliner Ambulance Future ownership: 1971-1973 Wayne Sentinel Suburban Ambulance |
#6
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If your compressor isn't starting, then check to see if it has the thermal overload protection device somewhere in the electrical line. If this is bad, then the system will not start. I suggest that you check your factory service manual for location and testing procedure. |
#7
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How was the leak detection done? If they used an electrical probe, it doesn't always locate the leak. Best method is to install a can or two of Freon with black light dye or yellow dye. Your car has a very large system, and a leak can be anywhere in the system, including the rear evaporator which is difficult to do a leak detection on. On large systems, I pull a vacuum for a couple of hours, and then add a two cans of Freon with dye, and then pressurize the system with nitrogen, to push the dye to all points of the system. Sometimes even that doesn't work, and you have to start breaking the system apart and install all new seals, and assume that is the problem. If that doesn't cure the problem, then you have to put the full charge of nitrogen into the system, and using a special soap mixture, start spraying the hoses, and hope that you will find the leak. It is time consuming, and you use up quite a bit of expensive supplies before you can find the leak.
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#8
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The ac in the front compartment works fine, Im just not getting any cooling in the back. I was thinking the line might be stopped up somehere, because all the hoses are hooked up.
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#9
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The valve in the rear evaporator may be bad.the 134a is what you charged it with? Most of them of have seen were a cobble of factory hoses hooked togeather. One may want to change them to new hose. They could be broken down inside.
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drop in for coffee anytime |
#10
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If the hoses were "stopped up", whatever was in the hoses, would have killed the front air conditioning system. Most likely, the expansion valve has failed. It can't be fixed without draining the system of Freon, and tearing into it. I suggest that you have a professional air conditioning service person take a look at the system.
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