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#1 |
Senior Member
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Location: kennewick, WA
Posts: 1,508
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AC compressor relay and Trinary switch wiring question
I am wiring in a stock Denso (new replacement) ac compressor, and wiring the compressor with a trinary switch. In the research I’ve gathered on this I think I’ve drawn this correctly. Since this is my first time doing this task I am hoping someone can tell me if I’ve done it right or what I’ve done wrong/you would do instead. Hoping there is people with more experience than what I have in this department before wiring it in so it’s done right the first time.
The company who went through the harness left the green/white wire labeled “AC Compressor” and a grey/black wire labeled “AC Request”. I attached a copy of how the trinary switch manufacture recommends it be installed. I basically replaced the ac thermostat switch with the compressor relay, and using the ac switch in the cab to trigger the relay. Any help is appreciated Posted via Mobile Device |
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#2 |
Registered User
Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: AC compressor relay and Trinary switch wiring question
Where is the ECM in your diagram? You want the ECM to control the compressor so that the added load on the engine is compensated for by the ECM. Usually a/c request is straight to ECM (through HP cutout switch) and the ECM output (pin 43, ground output) goes through the relay. Fan request is via the ECM as well. Why do you need a trinary switch? If you want fans on when a/c compressor is on, then just wire the fans through another relay in series to the a/c compressor relay (a/c relay triggers fan relay).
Note: Your a/c on/off wire (from control panel) IS the a/c request wire. https://lt1swap.com/99-02acwiring.gif Last edited by Davidf; 09-21-2021 at 12:00 PM. |
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#3 |
Senior Member
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Location: kennewick, WA
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Re: AC compressor relay and Trinary switch wiring question
I’m using a trinary switch because it will turn the ac compressor on and off at set pressures plus turn the electric fan on.
I think i solved my question, let me know what you guys think.
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#4 |
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Join Date: Nov 2011
Location: Idaho
Posts: 857
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Re: AC compressor relay and Trinary switch wiring question
That switch will help to keep the compressor from becoming a grenade and what he CO said.
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#5 |
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Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: AC compressor relay and Trinary switch wiring question
I still think a lot of functionality is missing. With this (above) wiring diagram, ECM control of the compressor is not present. Why not some form of:
A/C on/off from fan switch ->HP cutout on back of compressor ->ECM pin #17 (a/c request). ECM pin #43 (ground output) -> compressor relay -> compressor a/c LP cycling switch (or trinary switch, low side, I suppose) -> ECM pin #55 Condenser fans can be triggered by the compressor relay above so they come on whenever the a/c is on...good practice. Or, you can use fan 1 or 2 output from the ECM. Tell your tuner to trigger the fan output with the a/c request. Last edited by Davidf; 09-27-2021 at 05:30 PM. |
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#6 |
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Join Date: Mar 2020
Location: The Woodlands,Tx
Posts: 576
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Re: AC compressor relay and Trinary switch wiring question
going thru the same process of getting my ac working. when I got my harness back from the rebuilder he left a wire on it saying AC. I called and asked why he left it on there because I said no to ac on the build. He said they made a mistake just ignore it. Now I am wondering if he didn't do me a favor by leaving it. My question is is this wire connect to 12v or a ground or does it connect to the compressor and the compressor tell the ECM to increase rpms to handle the extra load. or connect to a relay terminal. Assume it is pin#17.
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#7 | |
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Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: AC compressor relay and Trinary switch wiring question
Quote:
On the other hand, if you let the ECM control the compressor, then the ECM anticipates the added load and compensates almost imperceptibly. And, the ECM can cut out the compressor as necessary such as during starting and full throttle, etc. For ECM control of the compressor, ECM pin #43 must control the compressor. Pin #43 is a ground output and must only be used to control a relay. Last edited by Davidf; 09-27-2021 at 05:42 PM. |
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#8 | |
Senior Member
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Location: kennewick, WA
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Re: AC compressor relay and Trinary switch wiring question
Quote:
Did he leave the factory plug for the ac compressor on your harness?
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#9 |
Senior Member
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Location: Southern California
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Re: AC compressor relay and Trinary switch wiring question
Would like control fans and AC as Davidf is pointing to. From my research this will not work with the e67 ecm.
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Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746 |
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#10 |
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Join Date: Mar 2012
Location: Woodbury, Ct.
Posts: 1,685
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Re: AC compressor relay and Trinary switch wiring question
I have a Vintage Air setup and use the trinary switch as they suggest. The fans only kick on when a set pressure is reached not just when you turn the AC on. I have never had any problems with idle. I have the AC request wire in my harness as well, but it is not being used.
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#11 |
Senior Member
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Location: kennewick, WA
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Re: AC compressor relay and Trinary switch wiring question
I am adding a low pressure cut out switch since the compressor is not cycling and freezing the evaporator. This is an updated diagram that I am asking Ls1nova71 to look at and verify. I moved the AC Request wire to terminal 87 on the compressor relay. I did that so the idle is bumped up only when the compressor clutch is on.
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#12 |
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Join Date: Dec 2009
Location: Independence Mo
Posts: 4,119
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Re: AC compressor relay and Trinary switch wiring question
That looks like it should work. The only thing I'm not positive about is the back feeding 12v to the AC request wire as I have never hooked one up that way, but I have heard it may bump the idle a bit, but again I have no first hand knowledge of it.
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My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html |
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#13 |
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Join Date: Nov 2014
Location: Austin
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I tried....
Do this, you don't need a trinary switch. Trigger the fan relay off of the compressor relay. Ignore PCM pins 33 and 11. [IMG] ![]() Photo courtesy of lt1swap.com Last edited by Davidf; 10-14-2021 at 02:17 PM. |
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#14 |
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Re: AC compressor relay and Trinary switch wiring question
Thank you
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#15 |
Senior Member
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Location: Southern California
Posts: 2,820
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Re: AC compressor relay and Trinary switch wiring question
Maybe late, I am still working on my project and still needing to address this. Fans on with compressor is not an option for me. Modern vehicles do not do that.
Found this informative thread from some time ago https://lateral-g.net/forums/showthread.php?t=40215 It is lengthy, so a long read. A lot of good info. From what I read there is zero reason to turn fans on with compressor. Gives me hope that I can use the pwm fan control with its advantages from my e67 ecm. Edit- maybe should have pointed out there is info on installing a stock gm pressure switch and connection to ecm. If you want stock type fan and a/c operation the thread is a good read if you can get though it.
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Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746 Last edited by Richard; 01-19-2022 at 02:26 AM. |
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#16 |
Registered User
Join Date: Nov 2014
Location: Austin
Posts: 749
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Re: AC compressor relay and Trinary switch wiring question
Hmm, I believe the condenser fan runs anytime the compressor is engaged on all of my BMW's. Albeit at a slow or high speed depending on need. But, it runs. Why would you NOT want the fan on when the compressor is engaged. The more the condenser is cooled, the more efficient the a/c system will be. The more efficient, the more fuel that is saved as the compressor will cycle off more often.
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#17 | |
Senior Member
![]() Join Date: Dec 1999
Location: Southern California
Posts: 2,820
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Re: AC compressor relay and Trinary switch wiring question
Quote:
Older vehicles such as the 67-72 trucks use a clutch on the fan to disengage it when not needed. It is regulated by heat. The electric sensors are just taking this a step further. There was nothing to fully engage the fan when a/c was turned on and the ac worked fine.
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Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746 |
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