NEED HELP AC compressor clutch allways engaged
- Thread starter yazan
- Start date
I would start with the basics first. Have you tried a different relay? Maybe something inside the relay is stuck. Next would be to check the control panel. Maybe a switch or button is stuck.
To engage the compressor clutch the PCM grounds one side of the relay coil. The other side of the relay coil is powered through the ignition switch. So if the wire going from the A/C relay to the PCM gets worn somewhere and grounds out then the compressor will run continously.
It is also possible for the relay to fail and get stuck I suppose. I just haven't seen that happen on these low power relays.
Swap out the A/C relay for the high beam headlights and see if the headlights stay on.
Mooseman
Moderator
And just something to be aware of, if you have it set to defrost or defrost/floor, the A/C compressor will run to remove moisture from the air. There is no way to turn it off, even if you push the A/C button. In any other setting it can be turned off.
Turning the whole system off (auto HVAC) or the fan off (manual HVAC) should turn off the compressor. If replacing the relay doesn't solve it, check to see if the PCM is sending the ground signal to the relay. If so, something is falsely telling the PCM that A/C is being requested. Look at the schematics to follow the wiring.
Turning the whole system off (auto HVAC) or the fan off (manual HVAC) should turn off the compressor. If replacing the relay doesn't solve it, check to see if the PCM is sending the ground signal to the relay. If so, something is falsely telling the PCM that A/C is being requested. Look at the schematics to follow the wiring.
- Jul 11, 2013
- 183
i did , i replaced the relay with a new one -spare - and also swapped it with similar ,
it's engaged even with engine off ! and i checked the buttons its not active , also i disconnected the rear hvac control unit to see what will happen
yes the auto ac have some weird problems i have many in my old tb , but my new ev is manual
now ,, what is driving me crazy is how that could happen if the the whole vehicle is off and engine is off and even the key is removed from the cylinder ? , its suppose to be every thing is off when engine is off !
so maybe the controllers and pcm is out of concerns ,
i will start with wiring .......... maybe short or open circut!?!?!
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Let me restate somethings to get the situation clear in my mind:
(1) Remove the relay and the clutch releases.
(2) Turn off and remove the key and the relay remains engaged.
Query: Can we assume ALL wiring in the truck is as it was when it rolled off the factory floor? NO changes to audio, no added lighting, no added remote starts, security, NOTHING altered?
The relay coil that should only have power when the key is at RUN or START would have to be getting power from somewhere and at the same time the control wire from the relay coil to the PCM would have to be grounded out somewhere. Seems unlikely for both of these failures to occur.
Mooseman
Moderator
Like @TJBaker57 said. With key off, there should be no power able to get to the relay and clutch. It is possible that the PCM for that circuit is a normally closed contact and sends ground by default, which would explain why they would have a switched + on the other side of the relay. To confirm this, put the relay in and turn on the ignition (not running) and see if the clutch disengages.
With key off and relay in, check if there is power at fuse 22 (IGN E), if there is, pull that fuse and see if the clutch disengages. If it does, then something is feeding that fuse when it shouldn't. If it doesn't (relay still powered), then something between the fuse and relay is feeding that circuit. Test and report your findings.
PS: Do not run the compressor in this state as it is a cycling clutch system and if the PCM is unable to shut off the compressor, it can either freeze up the evaporator or, worse, overpressure the high side and explode.
With key off and relay in, check if there is power at fuse 22 (IGN E), if there is, pull that fuse and see if the clutch disengages. If it does, then something is feeding that fuse when it shouldn't. If it doesn't (relay still powered), then something between the fuse and relay is feeding that circuit. Test and report your findings.
PS: Do not run the compressor in this state as it is a cycling clutch system and if the PCM is unable to shut off the compressor, it can either freeze up the evaporator or, worse, overpressure the high side and explode.
In my tests the PCM is either open to ground or a high resistance to ground depending on orientation of the test leads. (I got like 27k one way and open circuit the other)
- Jul 11, 2013
- 183
i tapped a wire at the ac compressor socket to a testing lamp with long wire and i put that lamp on the front glass to monitor while I'am testing and following the diagrams under hood and inside the car at front and rear hvac
i think the pre owner did something to the rear hvac , near the blower motor , i saw a wires that dont look like oem work > tomorrow I will remove that plastic covers and I think I had to remove the 3rd row seat for a full access to the unit
until now 2 relays worn out "stuck engaged" , i don't know how and why ! only the relay get damaged , and the ac fuse is still ok , so i make a simple test and touched the ac clutch wires to see if the fuse will blown or no , and it does , blowned !
i noticed that the relay bottom right pin is hard to seat .( that feeds the ac clutch as described in @TJBaker57 post )
tomorrow i will keep testing , and I will keep updating the post
BTW thanks for the reminder about not turning the ac on as long it will not disengage at all and will damage the system , also your advised "in another post" scan app "scan gauge pro" and car gauge pro , detected a P0530 A/C Refrigerant Pressure Sensor A Circuit Malfunction , witch not detected by torque pro app and that code lead to that point you talked about , the switch is trying to disengage the clutch but no response
Thanks for that app advise
and thaaaaaanks all @Mooseman @TJBaker57 @Mektek @c good for the very helpfull info
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- Jul 11, 2013
- 183
Ok. The first Update .I believe he had a problems with the rear hvac control unit , so he disconnected the rear controler and make the rear fan control (that near the shifter ) operates with direct wires to the rear fan . and guess what? Where he take the source that feed the fan 1/2/3 speed signal from?
Hot 12v? No
Accessories wire? No
Rear cegar lighter ? No
Ign1 or ign2?no for sure no
He had to smarter than this and tap it to the dome light wire. That controller by the dome in headlights switch!
That feed the dash and buttons bulbs. So if its sunny outhere or the dash lights was of so there is no power to the rear hvac.
I hope I describe it clear
Hot 12v? No
Accessories wire? No
Rear cegar lighter ? No
Ign1 or ign2?no for sure no
He had to smarter than this and tap it to the dome light wire. That controller by the dome in headlights switch!
That feed the dash and buttons bulbs. So if its sunny outhere or the dash lights was of so there is no power to the rear hvac.
I hope I describe it clear
Attachments
Mooseman
Moderator
I hate bad hackery like this instead of actually fixing the problem. Good on you for finding it.
flyboy2610
Member
One of those things that make you shake your head and ask: Why did they DO this??!!
A fun YouTube channel that is full of such things is https://www.youtube.com/c/JustRolledIn/videos
A fun YouTube channel that is full of such things is https://www.youtube.com/c/JustRolledIn/videos
- Jul 11, 2013
- 183
