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A/C only works when I jump relay?

Tiny
HARDY PANCHAL
  • MEMBER
  • 2008 ACURA RDX
  • 2.3L
  • 4 CYL
  • TURBO
  • 4WD
  • AUTOMATIC
  • 144,000 MILES
So, A/C wasn't working, there was less than 10PSI in it, I jumped the relay to get 30PSI in it. Now when I install the relay, I still have no A/C clutch engagement but when I jump the relay A/C works fine and blows cold. When I tested with power probe, I have power on the 2 prongs but no ground from ECM->ACrelay which if I power probe the relay with ground while the relay is just half installed, everything works fine. Also, when the condenser fan turned on, it rapidly clicks after running for a minute or 2 and then fans stop and after another 30seconds the pressure relief valve blows out some of the refrigerant. I believe the condenser fan control is the problem. What controls the condenser fan relay?
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Friday, July 7th, 2023 AT 3:37 PM

8 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
At 30 PSI that is not enough to trigger the pressure witch to turn the system on. With the system off connect the recharge can and open it until the pressure comes up to about 60 PSI and let it sit that way for about a minute. Then start the engine and turn the system on full cold and continue to charge the system, these two guides should help us fix it:

https://www.2carpros.com/articles/air-conditioner-how-to-add-freon

and

https://youtu.be/4EqdrBVb0sY

Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.
.
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Saturday, July 8th, 2023 AT 12:06 PM
Tiny
HARDY PANCHAL
  • MEMBER
  • 5 POSTS
Pressure at 30psi while clutch is engaged and everything's working, ambient temperature numbers pressure when it's not. Problem is it cuts out while working fine, and the clutch cuts out with the fan simultaneously but repeatedly after 4mins of good operation and perfectly cold AC! I'll change the pressure switch for tomorrow and report back. But it works fine randomly after few minutes of breaks but after about 3-4mins of good operation, it cuts out. And no power at the clutch after. Also no power 2 the fans after when it cuts out. Tried jumping the pressure switch between the power and signal wire but it didnt kick the clutch or the fan on. From what I hear, the ECU doesn't want read 5v. It wants to read between 3.5-4.7v from the signal wire of the pressure switch, is that true?
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Sunday, July 9th, 2023 AT 2:02 AM
Tiny
HARDY PANCHAL
  • MEMBER
  • 5 POSTS
No luck changing the pressure switch. What else controls the signal from ecu to relays that would make it not work randomly?
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Sunday, July 9th, 2023 AT 1:02 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Yep, that sounds correct. I wonder what the high side reading is when it cuts out? Please check out this guide can well, and I have included the A/C system wiring diagrams so you can see how the system works.

https://youtu.be/4EqdrBVb0sY

Check out the images (below). Please let us know how it goes.
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Monday, July 10th, 2023 AT 9:55 AM
Tiny
HARDY PANCHAL
  • MEMBER
  • 5 POSTS
Display shows me pressing the A/C button on and off, but the ECU is not reporting to the Snap-On versus that the A/C switch is commanded on or off. Can anyone look at the diagram and tell what could be faulty here? I revised all the pressures and vacuumed the system and refilled it with the right charge, new relays and new pressure switch.
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Monday, July 10th, 2023 AT 12:20 PM
Tiny
KEN L
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I would check the IG2 power inputs (green wire) on both the drivers and passengers side control switches.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Please check with the key on. Let me know what you find.
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Tuesday, July 11th, 2023 AT 10:10 AM
Tiny
HARDY PANCHAL
  • MEMBER
  • 5 POSTS
Also, I'd like to note that. This car's climate control inputs go through a canbus module. It's getting power since dash says A/C is on. And the compressor even turns on and shuts off.
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Tuesday, July 11th, 2023 AT 3:41 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
You might have a bad MICU, we should perform a CAN scan, you can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

Please go over these guides and get back to us.
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Thursday, July 13th, 2023 AT 9:13 AM

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