Ok, I have an 86 Firebird with the 2.8 V6 and an auto trans. The AC system was dry for some time, so it was recharged with R134a. My issue is this. If I pull off the plug on the low pressure switch and jump the contacts in the plug, the compressor will not engage. However, if I attach a test light to ground and probe a wire on the AC control relay, the compressor kicks in and will run until I remove the ground. I used the test light to verify power going to the low pressure switch and there is. No power to the compressor until I ground the relay. The relay will then click and engage the compressor. There is 24 oz of R134 in the system now. This should be enough to cycle the compressor but to no avail. I am lost as to what the problem could be as I have heard simply jumping the low pressure switch will make the compressor energize and it does not. If the relay was bad, it would not click and engage when grounded. What else could it be?
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Re: AC compressor will not energize
First thing you should check is all your grounds, on the body and your battery connections. Also double checked to make sure you have the air conditioning on with the fan on. If this is good the next thing to do is to get a wiring diagram. Verify that there's power going into the switching and coming out of the switch. Next find the compressor relay verify that there's power going two it. If this is good use your tests light to ground out the relay. If this works find out where the ground wire goes to the computer or the wide open relay. Good luck.
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The system has to make the low pressure limit switch before it energizes the system. If you have 12v at the low pressure switch and verify that there is enough refrigerant in the system to make the switch, try jumping out the switch. If the compressor energizes the coil you are looking at a bad switch. If the compressor clutch does not energize I would look to the AC relay or maybe a bad switch at the control head.
WARNING: CHECK TO ENSURE THAT THE TRANSMISSION IS IN THE PARK/NEUTRAL POSITION WITH THE PARKING BRAKE APPLIED.
The starter relay is located in the Power Distribution Center (PDC) in the engine compartment. Refer to the PDC label for relay identification and location.
Remove the starter relay from the PDC as described to perform the following tests:
A relay in the de-energized position should have continuity between terminals 87A and 30, and no continuity between terminals 87 and 30. If OK, go to Step 2. If not OK, replace the faulty relay.
Resistance between terminals 85 and 86 (electromagnet) should be 75 ±5 ohms . If OK, go to Step 3. If not OK, replace the faulty relay.
Connect a battery B+ lead to terminals 86 and a ground lead to terminal 85 to energize the relay. The relay should click. Also test for continuity between terminals 30 and 87, and no continuity between terminals 87A and 30. If OK, refer to Relay Circuit Test procedure. If not OK, replace the faulty relay.
RELAY CIRCUIT TEST
The relay common feed terminal cavity (30) is connected to battery voltage and should be hot at all times. If OK, go to Step 2. If not OK, repair the open circuit to the PDC fuse as required.
The relay normally closed terminal (87A) is connected to terminal 30 in the de-energized position, but is not used for this application. Go to Step 3.
The relay normally open terminal (87) is connected to the common feed terminal (30) in the energized position. This terminal supplies battery voltage to the starter solenoid field coils. There should be continuity between the cavity for relay terminal 87 and the starter solenoid terminal at all times. If OK, go to Step 4. If not OK, repair the open circuit to the starter solenoid as required.
The coil battery terminal (86) is connected to the electromagnet in the relay. It is energized when the ignition switch is held in the Start position and the clutch pedal is depressed (manual trans). Check for battery voltage at the cavity for relay terminal 86 with the ignition switch in the Start position and the clutch pedal is depressed (manual trans), and no voltage when the ignition switch is released to the ON position. If OK, go to Step 5. If not OK, check for an open or short circuit to the ignition switch and repair, if required. If the circuit to the ignition switch is OK, see the Ignition Switch Test procedure.
The coil ground terminal (85) is connected to the electromagnet in the relay. It is grounded through the transmission range sensor only when the gearshift selector lever is in the Park or Neutral positions. Check for continuity to ground at the cavity for relay terminal 85. If not OK with an automatic transmission, check for an open or short circuit to the transmission range sensor and repair. It is grounded by the PCM if the conditions are right to start the car. For automatic trans. cars the PCM must see Park Neutral switch and near zero engine rpm. For manual trans. cars the PCM only needs to see near zero engine rpm. To diagnose the Park Neutral switch of the trans range sensor refer to the transaxle section for more information. Check for continuity to ground while the ignition switch is in the start position. If not OK and the vehicle has an automatic trans. verify Park Neutral switch operation. If that checks OK check for continuity between PCM and the terminal 85. Repair open circuit as required. If OK, the PCM may be defective
The AC compressor may need recharged, or repaired / replaced. A lot of times what happens is through the winter AC units aren't ran so the seals recieve no oil and dry out letting coolant escape. Sometimes you can get lucky and a recharge (which contains oil essential for your seals) will do it - if they are too dry however, you will need a new compressor. You can have your AC unit recharged at nearly any dealership except in the state of California. Hope this helps.
The very 1st thing you do is see if the AC system has lost its charge of refrigerant. If the system is low on charge then the relay will not engage because it receives no signal from Compressor cycling switch which in most Fords is located in the low side AC line from the compressor, the low pressure line is the larger of the 2 lines from the AC compressor..
There are 4 main issues to the AC on a car (not including wiring or more advanced troubleshooting)
1 Recharge (Cheap do it your self Recharge kit from auto shop)
2 The belt that it drives it (Least expensive Replace Belt)
3 The clutch on the compressor (Expensive because you have to puge the system R/R the compressor check the evaporator for damge repressurize system and test.
4 The compressor went bad (Most expensive Usually when a compressor fails it will send metal shavings throughout the system that will cause the system to fail again the soulation is the same as 3 but now you need to replace the evaporator and flush all the AC lines out.
Do you hear the air conditioning compressor switch on (with the engine
running) when you turn on the air conditioning from inside the car. Get a
friend to turn on and off the air conditioning while you listen with
the hood open engine running you should hear a clicking sound on and off
each time the a/c is cycled on and off or the a/c clutch is not locking
up the compressor. This may be due to many things (bad clutch, bad
compressor, no power to controls or compressor clutch) but it could be a
sign of low charge the system has a low pressure switch which prevents
the system from being energized if the system has low refrigerant
charge. By protecting itself it prevent catastrophic failure of the
compressor and ensuing damage to the rest of the a/c system if the
system looses it charge. You will need to have the system checked out by
someone experienced in air conditioning work who will attach pressure
gauges to your car and see if the refrigerant pressures are OK. The
system naturally looses some refrigerant over time but if the system
constantly looses charge then it has a leak that must be investigated
and repaired before just recharging the system
Hi, oK ASSUMING THERE IS THE PROPER AMOUNT OF FREON IN THE SYSTEM (2.0 LBS) THE SYSTEM IS PROBABLY LOGIC LOCKED.THIS CAN HAPPEN WHEN THE CADILLACS HVAC CLIMATE CONTROL HEAD GETS CONFUSED,USUALLY AFTER A RECHARGE.HERES WHAT U CAN TRY.REMOVE THE NEG BATTERY CABKE FOR 1 MINUTE,THEN RECONECT IT,START THE CAR AND PUT THE AC ON (60 DEGREES FULL FAN) THAT SHOULD DO THE TRICK HOPEFULLY. THAMKS RAY.
the problem you will have is the trans for the v6 will have less friction material in it so it will havea very short life in a v8 car.. so no its not the same trans internally but as for the fit if the v6 is a 4.3 yes a direct fit for the v8 ..