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A/c question: low pressure switch was corroded...replaced it, recharged system, seems not to have leak as pressure has stayed the same all day, compressor sounds like it switches on but no cold air blows...ideas to check next?

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SOURCE: 2000 Jeep Cherokee Air Conditioner

If compressor isn't kicking in, check the connector atop the a/c accumulator, beside the coolant recover tank, in the engine compartment. That connector is atop a black bottle, and the connector goes to the low pressure switch. These switches do fail, and you can jump a wire across the connector terminals to see if the compressor comes on (engine running). As this circuit provides part of the ground path from the compressor clutch, if the switch is open, the compressor will never turn on. If the switch is failed, it can be replaced without opening the a/c system. Just disconnect the connector, unscrew the switch, replace it, and reconnect the connector.

Posted on Aug 08, 2008

emissionwiz
  • 61249 Answers

SOURCE: 1999 GMC Sierra 1500 A/C blows warm air when idling

the low pressure port is the charging port, this port is either in the low pressure line or the accumulator that the low pressure lines to to (can shaped object), the low pressure line is the larger of the two lines from the compressor.

Posted on May 27, 2009

  • 1 Answer

SOURCE: Dodge Ram AC not blowing cold

By pass both pressure switches one at a time with small wire or a paper clip. If comperssor kicks on replace the swich that you bypassed.
if not it could be the fan clutch ot the compressor. Compressor runs about $400.00

Posted on Jun 23, 2009

  • 38 Answers

SOURCE: A/C Blows cold air at night and in the morning

My 96 accord had the same prob. if you don't have a leak you need to make sure
of that first if no leak and not over charged ( my 96 accord holds 22.9 ounces of 134 )
anyway the fan on left side of motor was bad I replaced it and it works great.
Day/Night and inbetween

Posted on Jun 28, 2009

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My 99 tahoe a/c is not working and is recharged properly. The clutch does not engage on the compressor and the compressor is new. What can the problem be


if you did the recharge then check the gas pressures as there are two main switches that control the ac operation
one is a high pressure switch which stops operation if there is excessive gas or a blockage and the other is a low pressure switch which stops operation if the gas has leaked out
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You are bypassing the safety mechanism built in to prevent compressor damage. You either have one of two conditions, You truly have a low pressure condition(menaing you need an evac and recharge(fill the system with r134a gas) or a bad pressure switch. The switches are inexpensive replacing it will cost less than the charge to diagnose it, as such i would have it evacuated change the switch then have it recharged and a UV die added in so any other potential leaks can be found

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1 Answer

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Sounds about right. The switch itself is relatively cheap -$20-40, what you are paying for is the special handling that is required to remove R12, the labor to remove the switch, vacuuming and refilling the system.

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