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Its almost like getting no signal to the relay no power to compressor or pressure switch when jumped from relay pins works great any suggestions

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  • Master
  • 549 Answers

This is a symptom of a bad relay. It could be burned relay contacts or the electromagnetic coil inside of the relay may be burned out.

Posted on May 15, 2014

  • 1 more comment 
  • John Barnett May 15, 2014

    Hmm I tried the horn relay in its place same relay still to relay no power wondering what sends signal

  • Hjalmer Lamminen
    Hjalmer Lamminen May 16, 2014

    That sounds like a problem with the air conditioner controls on the dash.

  • John Barnett May 16, 2014

    thank you sir I will check that the ac light comes on but that don't mean it works

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check the crankshaft sensor

Posted on Aug 14, 2008

SOURCE: volkswagen vanagon air conditioning system

Most of the control relays for the vanagon AC can be found on the drivers side D pillar under the plastic or in the cabinet if you have a cabinet. Best to buy a 'Bentley' factory service manual to help out. Cane Rattler...1989 Vanagon

Posted on Aug 29, 2008

ftw1952
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SOURCE: 99 Suburban A/C Not working

The A/C pressue switch may be bad as well. Also the mode switch on the control head inside the vehicle. There are many other exsisting problems pertaining to a/c. I suggest a manual from Auto Zone for many faults can be noted especially wiring can be at fault

Posted on May 23, 2009

  • 1348 Answers

SOURCE: 1996 lincoln towncar. No a/c compressor engagement unless jumped

the control unit is no good.i had a similar situation with a 98 tracker,and installed a switch to give it a ground for the compressor relay that comes from the a/c computer module.
it works good and goes on and off with the a/c switch.

Posted on Jul 18, 2009

  • 9 Answers

SOURCE: My ac is not working on my 2000 mustang 3.8L. I'm

You were close! Most Fords have a CCRM (Continuous Control Relay Module) thats on the passenger side fenderwell. It has 4 relays: one for the AC compressor cluth, one for the fuel pump, and two for the electric fan (high- and low-speed.) The AC is the one that fails the most. You can replace the CCRM by removing the intake air filter box and working through the fenderwell openings. If it gets to difficult you must remove the wheel and splash cover to replace it from the wheel opening.

Posted on Sep 21, 2009

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1 Answer

A/c clutch wont engage. the compressor and clutch are good i jumped the pins on the pressure switch,didnt work. i checked the relay.i jumped the pins where the relay goes and got it to engage.


there are two pressure switches in an ac system
one switch prevents the compressor from running if there is too much gas
the second is to prevent the compressor from running if there is insufficient gas
from what you describe , one of those switches ( most likely no gas) is the switch
check for oil dust around the fittings , condenser or have an ac specialist check for leaks and regas

Sep 29, 2016 | 1999 Honda Civic

1 Answer

Compressor clutch engages when I jump the relay, and I already bought a new relay. What could be preventing the compressor from recording power.


The compressor from recording power ? First off what make , model an year vehicle ? When you jump the pins where the relay plugs into , By the way that should be pin's 30 & 87 .look on the bottom of the relay .Besides 30 & 87 you will also see pin's 85 & 86 ! 85 ,86 are the control side . When you push the A/C button on the control head ,depending on make , model an year vehicle , the control head sends a turn on request to the BCM - body control module or right to the PCM - engine computer .The PCM will then energize the compressor clutch relay ! Is there control from PCM ? Before the the relay will be energized the PCM looks for a signal from high an low pressure cut out switches . Your best bet would be to take your vehicle to a qualified repair shop .

Aug 05, 2016 | Cars & Trucks

1 Answer

2003 no power to compressor


defective harness... low pressure switch (mounted on low side or on accumulator) relay or control switch.. try the low pressure switch on suction line... in screws on to a shrader valve. the pins on the harness to the switch can be jumped with a paper clip momentarily to check to see if compressor comes on..

Oct 09, 2013 | 2003 Chevrolet Silverado 1500

1 Answer

What energizes ac relay on 2005 freestar


The low side pressure switch in the AC low pressure line signals the PCM (computer control) to close the AC compressor relay and raise the idle speed. If the system is low on refrigerant charge the relay will not allow the system to engage the compressor, this is because the oil that lubricates all the works is suspended in the AC refrigerant, if that is low then the system gets no lubrication and will quickly seize up..

Mar 23, 2012 | 2005 Ford Freestar

1 Answer

Jumped the relay and compressor came on and system charged it was blowing cold. When I put relay back in the compressor will not come on. I swapped relays and still nothing. But every time I jump it it...


So the relay coil is not being energized. You will need to determine why. It could be the ground signal from the PCM, which is effected by the control panel A/C switch or else it is the positive signal from the 10 amp CRUISE fuse, which must pass thru the pressure switches (high and low). First check the fuse. If the fuse is good, use a 12 volt test light to probe the relay socket to see which signal is not getting to the relay. Connect your test light clip to chassis ground, start the car, turn the A/C on, and probe the relay socket. There should be 2 hot terminals in the socket--one from the 10 amp compressor fuse, which you have been using to power the clutch, and one from the pressure switches. If you don't get this second hot terminal, try jumping each pressure switch connector one at a time to see which one is not closing. If you DO get both hot signals, the problem is the signal from the PCM. Move your test light clip to battery positive and probe the relay socket again. If the negative signal is absent from the relay socket, only the clutch terminal will show any voltage. If this is the case, you will first need to check the continuity of the wire (dark green with a white stripe) from the PMC connector 2 pin 47 to the relay socket. If the wire is good, the problem may be in the control panel. If you get this far and/or you get stuck along the way, please get back to me.

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Jul 24, 2011 | 2001 Cadillac DeVille

1 Answer

If I strap terminal 3 to 5 on the compressor relay the compressor comes on. What controls the compressor relay?


THE LOW PRESSURE SWITCH
SYSTEM IS PROBABLY LOW IN FREON
TO CONFIRM LOCATE LOW PRESSURE SWITCH AND JUMP
THE TWO PINS IF COMMPRESOR ENGAGES THR SYSTEM IS LOW
DONT LEAVE IT JUMP YOU WILL BLOW UP COMPRESSOR
NEEDS FREON TO CARRY COMRESSOR OIL TRUE OUT SYSTEM

May 07, 2011 | Chevrolet Lumina Cars & Trucks

2 Answers

A/c compressor clutch will not engage


In this case, I would suggest that the low freon pressure switch has activated and prevents the compressor from running and damaging your system in your 15 year old vehicle. To prove this, find the switch and short the switch out and see if the compressor kicks on.

How do you fix this? Get the system recharged. Also have the mechanic check for leaks. The freon escapes somehow ...

Thanks for your question today.

Mar 03, 2011 | 1996 Cadillac DeVille

1 Answer

A/c clutch relay not getting signal from wire going to pcm.jump relay works fine. repl.a/c switch in dash a year ago


Check freon pressure while running on low side. Low pressure will cause compressor not to engage.

May 15, 2010 | 1992 Pontiac Bonneville

2 Answers

1996 lincoln towncar. No a/c compressor engagement unless jumped


the control unit is no good.i had a similar situation with a 98 tracker,and installed a switch to give it a ground for the compressor relay that comes from the a/c computer module.
it works good and goes on and off with the a/c switch.

Jul 18, 2009 | Lincoln Town Car Cars & Trucks

3 Answers

A/C Compressor not kicking on


The power to run the compressor clutch coil goes from the battery, to the AC Clutch Relay, somewere in the engine compartment fuse box, then it goes to the positive side of the AC compressor clutch coil; goes thru the coil, activating the compressor, and then goes to complete the circuit through another switch (high pressure protection switch) in the back of the AC compressor and finally reaching negative or Ground.

Disconnect the AC compressor clutch connector and using a 12 V bulb with 2 wires (test lamp) check the following:

1.- connect 1 lamp wire to battery neg; with the other check both pins at connector with the AC in the RUN (AC and ignition switch on ) you should have power in one side.

2.- connect 1 lamp wire to battery positive and with the other check both pins at connector, lamp should light getting the ground from the clutch connector thru the high pressure compressor switch to ground.

On the other side what makes the relay close and let the power flow to the clutch works with the low pressure switch, (if the freon pressure is too low it opens and kills the ground to the relay coil and that kills the compressor), that low pressure switch is in the low pressure side of the freon tubing, the fat pipe that comes from inside the firewall into the accumulator/dryer, a big aluminum cylinder sitting on the right side of the engine compartment in GM cars.

To know if the low press switch is the cause you can unplug it and connect both legs with a paper clip for a minute or two, no more, you don't want to damage the compressor. anyway if jumping the switch makes the compressor come alive and kick in, you either have low freon pressure or a bad switch; it's time for the pressure gauges and check how the compressor is pumping and that is better left to a pro.

By the way you said that your system is a R-12 system, have you considered switching to R-134a the new "ozone friendly" freon? to do that you need to evacuate the system with a recycling machine and pull vacuum in your AC, if it holds the vacuum for a while, then you can be sure that there are not leaks and then dump 1.5 or 2 pound (check the labels in the engine compartment) of R-134a into your system. it will be a good idea to put some fluorescent leak detecting dye in the system to check for leaks, just in case..

Jun 13, 2009 | 1992 Oldsmobile 88

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