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Lexus GX460 AC Clutch engages when relay is jumped


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Stromfu
New User

Jun 19, 2022, 12:09 PM

Post #1 of 4 (239 views)
  post locked   Lexus GX460 AC Clutch engages when relay is jumped  

I have a 2010 Lexus GX460 Base with 240k miles in which the AC clutch will not engage unless I jump the relay. Upon jumping the relay, it blows cold air.

I have replaced the relay and fuses, and checked all fuses. I have recharged the refrigerant with AC Pro, plus is blows cold when I jump the relay.

It also seems that I don't have heat, but not sure as it's the 90-100 temps around here.

I believe the GX460 only has one AC Pressure Sensor/Switch that is located near the HI pressure valve. I'm working my way backwards trying to determine what controls the AC Compressor Relay.

Is it a logical next step to replace the AC Pressure Sensor / Switch or is there something else that might be keeping the AC Comp Relay from closing to engage the clutch?

All suggestions greatly appreciated! Thanks!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 19, 2022, 1:21 PM

Post #2 of 4 (224 views)
  post locked   Re: Lexus GX460 AC Clutch engages when relay is jumped  

There are many things that will prevent the compressor from engaging. This is an Auto Temp Control system.

The compressor relay is controlled by the PCM and it looks at numerous inputs before turning it on. The system needs to be diagnosed properly, not just throw parts at it. You would need a professional scan tool to look at all the sensor values like AC pressure, coolant temp, ambient temp and commands from the control head, etc.. It also has a thermostat in the evap that can shut down the compressor.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Jun 19, 2022, 1:28 PM

Post #3 of 4 (222 views)
  post locked   Re: Lexus GX460 AC Clutch engages when relay is jumped  

Don't jump relays! Check wiring to it as best you can at least visually at that relay even back sides if you can.
Default seems OK that it can blow cool air at you doesn't mean pressure isn't too high OR perhaps enabled by a switch inside car. If that lights up it's probably OK or could you have left it off by mistake?
With A/C request fan(s) need to run or may not allow compressor pressure would be too high it would shut off.
AYOR with kits for charging A/C some may not be accurate or some used to have junk for sealer I don't see that anymore though.
In general A/C isn't so DIY friendly easy to overcharge a system but if a real 100F should run would be trouble if way over charged if cooler out doesn't take that much over!


Other: Even with the kit cans to boost systems that isn't the way to know charge is right. Only real way is from a well held vacuum then charge by exact listed weight or it's wild guessing to damaging you won't like.


Other stuff could be a well worn clutch to compressor should be about .020 by that many miles the air gap is probably larger than it likes if over .030 wouldn't usually engage but jumping things it might?
Most you can use a standard biz card if you can't measure it by a feeler gauge if you don't have one some a folded one paper isn't all the same thickness,


T



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 19, 2022, 2:55 PM

Post #4 of 4 (213 views)
  post locked   Re: Lexus GX460 AC Clutch engages when relay is jumped  

If it engages when you jump the relay, then the air gap is fine.

If you get the electrical issue resolved, then you will have to address getting the required charge level.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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