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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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Posted on Jan 02, 2017

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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

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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

  • 44 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
did you have the ac system checked for leaks before gassing it or replacing the ac compressor
lastly some systems have a relay that controls the ac and that can fail

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Where is low pressure switch to recharge freon for a/c

What year an model Oldsmobile ? Relay switch , low pressure switch . You would hook up the refrigerant to the low pressure side of the A/C system . This still confuses me , relay switch . Back in the day ,at the dealer we would use a jumper wire to by pass the low pressure switch to kick in the compressor clutch to draw in the refrigerant . Is this what you want know where it is or the low pressure side fitting where you hook up the refrigerant charge to . If you have not done this before I suggest you take it to a shop that does A/C testing . Your vehicle may need more then a recharge .

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Ac compressor will not kick in unless i ground the green wire to the low pressure switch when i do this it kicks in and works great

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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Replaced a/c compressor on 1994 chevrolet truck c1500 5.7L. Added refrigerant and pag oil (32/8) -compressor tries to kick in but can't seem to stay on and mist appears to be leaking out somewhere....

unless you can verify what the pressures are you will need to have a shop check it for you. Low pressure will give the symptoms you stated. Also if you did not vacuum all the air out before you added the stuff then a shop will have to perform a a vac and recharge. Plan on paying the piper if you did not do this yet. You can only accurately charge a system after a vacuum has been put on the system and then held there for a time to see if the vacuum stays.

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Need to jump compressor on to recharge refrigerant

You should not have to jump compressor to recharge a/c system, when adding freon low pressure switch will kick compr on, if it's not kicking on or it read low freon on your dash, replace both low pressure switch's, both sit along fire wall from left to right on a thin a/c line, when replacing these switch's make sure what ever freon in system is recover.

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The system is likley low on gas,causing the low pressure switch to dis-able the compressor clutch.
Check the low gas pressure switch by briefly looping the switch out of circuit.
If the compressor clutch now engages normally it confirms low system gas (Don't run for long like that or it will ruin the compressor).
Get the system re-gassed and checked for leaks.

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Several- The system should hold freon for years without leaking. There are pressure switches and they cut off the compressor with an undercharge and an overcharge. You need guages to measure the charge. There are testers the A/C shops have called "sniffers" which can detect a leak. If you have no leak then you need a technician to add or remove freon to get the concentration right. Or you need guages.

Jun 12, 2009 | 1997 Oldsmobile Aurora

1 Answer

AC low pressure switch leaking

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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