no power to a/c low pressure switch


royrokit

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2003 Ranger 4.0 Automatic. Have no power from (or to a/c off/on switch), out to low pressure switch, to high pressure switch and ultimately to Compressor. Have checked relay under hood and fuses under hood and passenger compartment and none blown. Kinda stumped here. Just not powered. Have not pulled Climate Control Panel to check for power there, but nothing unusual has happened to really warrant no power to control panel. Heater works fine, blower, everything but turning on a/c.
 


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adsm08

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If you haven't pulled the climate head and tested back there how do you know there is no power to the AC on/off switch?
 

royrokit

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Well the reason i haven't pulled the panel yet, is like I said , I've had no unusual occurances to think that anything could have arbitrarily just gone wrong back there, but you're right, I do need to find out if the plug is hot to the control, but as I said, everything else works except there is no power at the low pressure switch and I assume that is next in line from the off/on switch. I appreciate your response.
 

adsm08

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Well the reason i haven't pulled the panel yet, is like I said , I've had no unusual occurances to think that anything could have arbitrarily just gone wrong back there, but you're right, I do need to find out if the plug is hot to the control, but as I said, everything else works except there is no power at the low pressure switch and I assume that is next in line from the off/on switch. I appreciate your response.
And just exactly what kind of "unusual occurrence" are you expecting to precipitate, or indicate, than an electrical switch has failed, aside of course, from the item it controls to not work?
 

royrokit

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Ok. Since the connector to the a/c control usually plugs in and locks in by snaps, (acording to online searches) I'm sure there should be no reason for it to come unplugged. Everything else still works. No blown fuses, relays in outside fuse box have been tested and no problems. I am basically seeking information as to why it would just suddenly have no power. Do you have any other suggestions? Could it actually be the off/on switch itself? Is that a normal failure over time? The vehicle is never abused, the dash has never been diassembled for any reason. Everything on the dash panel works as normal as day one except, the a/c mode on the switch. Neither a/c or Max a/c works. Blows air through the proper vents, everything but feed power out to the system. Switch on the contol panel bad? I tested the relay, it's good and has good resistance of around .73, mynute resistance across 30 to 87 poles with 12v applied and good voltage, opens and closes. Tested fuse and fuse socket, there is power there . There is no power at the low pressure switch, the high pressure switch or the compressor.
 

adsm08

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Ok. Since the connector to the a/c control usually plugs in and locks in by snaps, (acording to online searches) I'm sure there should be no reason for it to come unplugged. Everything else still works. No blown fuses, relays in outside fuse box have been tested and no problems. I am basically seeking information as to why it would just suddenly have no power. Do you have any other suggestions? Could it actually be the off/on switch itself? Is that a normal failure over time? The vehicle is never abused, the dash has never been diassembled for any reason. Everything on the dash panel works as normal as day one except, the a/c mode on the switch. Neither a/c or Max a/c works. Blows air through the proper vents, everything but feed power out to the system. Switch on the contol panel bad? I tested the relay, it's good and has good resistance of around .73, minute resistance across 30 to 87 poles with 12v applied and good voltage, opens and closes. Tested fuse and fuse socket, there is power there . There is no power at the low pressure switch, the high pressure switch or the compressor.

The switch can just fail like that. It has contacts that take wear every time the switch is moved. If just the post that powers the AC system is worn out it would cause this.

I don't have the diagrams for that truck on hand, so I don't know if the AC pole gets its power from somewhere different than the rest of the system or not.
 

royrokit

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Ok. Thanks for you help with this. I will pull out that Control panel and check power to it and replace the switch if necessary. Will post the results to you. Thanks again
 


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