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Old 08-17-2017, 01:54 PM   #1
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BB A/C q

2000 BB TC1000 w/2 Carriers. Compressors are hung on the bottom of the engine, run off two separate belts.

Rear comp. is not getting 12v. I can feed 12v to it and runs fine. I guess the pressure sensor is not sensing the 134a is a bit low but not much.... maybe enough to cause this.

Problem: I can't find the sensor. Thought I'd ask first if anyone knows, otherwise I will tear into the loom and trace the wire. I need a tone thingy but.... All the A/C plumbing is under the bus. I guess it would be on the hard high pressure line somewhere?
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Old 08-17-2017, 04:03 PM   #2
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Sure sounds like low pressure on the freon. Maybe just get it recharged as the sensor is supposed to keep it from starting under low pressure. All a/c's loose pressure at some point in their lifetime. Have them check for leaks if you can't do this where you are.

John
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Old 08-17-2017, 08:05 PM   #3
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the most common place for the pressure sensor is up in the evaporator cabinet itself.. it may be in the liquid line or the suction line.. if its in the liquid line the unit typically wont start up at all after the freon leaks down to a certain point. if its in the suction line, you'll get excessive cycling of the compressor as the freon leaks down.. ands youll notice the vent temperatures going cool-cold-cool-cold .. most of these units also have a relay board either under the bus or up in the evaporator cabinet which is where the compressor power is fed from.. if one of the relays is bad or the fusae blows your compressor wont run..

the most common configuration is a Trinary switch in the liquid line.. it will have 3 wires.. and senses both low and high pressure.. and cuts power to the compressor if either condition is true.
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Old 08-17-2017, 11:10 PM   #4
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Thanks all, great info. Soon I will see what I can find.
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Old 08-18-2017, 01:41 PM   #5
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OK, the problem is the freeze up switch. Carrier PN AC201-501. Not that critical but I will try to locate one.

Thanks guyz


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Old 08-18-2017, 03:22 PM   #6
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did the pressure leak out of that little copper line? ironically there is freon inside that copper tube.. and then a spring attached to the knob.. as the freon cools off the pressure drops and opens the circuit.... you dont need a carrier specific product. any adjustable freeze protection switch will work..

along the lines of Danhard, vintage air, etc are some more common companies that likely have them. an adjustable one allows you to adjust how cold of air you want coming from the vents before it turns off the compressor..

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Old 08-18-2017, 04:42 PM   #7
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The tube looks intact and dry.

Thanks.
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