How to: AC Pressure Switch Delete

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How to: AC Pressure Switch Delete

Postby Corey » Thu May 07, 2015 4:05 pm

Edit: Rather than create a new thread, I've edited this one to create a How to:

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Original Post

I removed my AC a while back so I have the AC pressure switch shorted with a paper clip to keep the radiator fan working properly.

Since then, I've always thought it would be neat to re purpose the AC / ECON switch in the HVAC as a switch to manually activate the radiator fan when sitting in traffic.

I was thinking one way to do this was with the now disused AC pressure switch. But I'm not sure where the switch is connected. I took a look at the wiring diagrams and I THINK it goes the the radiator fan relay?

Anyone know any better or could help me track this down?

Thanks

Corey
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20 Gauge wire (closest colours I could find were blue and black). Can see the wire extensions crimped on and heat shrunk.
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Once the extensions were crimped on, I covered the new wires with plastic split coil and fed them through the firewall along with the engine harness. From there, I fed it under the airbox, behind the glove box, behind the radio, and then over the lower air duct toward the switch. The route doesn't really matter, and I may end up changing it down the road.

I do plan on acquiring some oem Toyota 2-wire connectors from Dr. Tweak which I'll solder in-line near the ECU so that I can easily disconnect this new harness without having to get at the switch on the driver's side.

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The factory switch. Im going to have some decals printed to cover the original text to match the new purpose of the switch.
Also, due to the nature of the Rad fan relay, I decided to install the switch upside down, otherwise the switch action would have been backwards.

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I rewrapped the harness using a combination of 3M electrical tape and "X-treme Tape". I used the 3M tape in the same areas as OEM to help bundle the wires together. The X-treme tape I used overall to wrap the sections of old electrical tape I removed. It's supposed to be good from -50C to +260C and something like 8000V. Time will tell how long it will hold up for. This was my first attempt at wrapping an engine harness.

X-Treme Tape
https://www.youtube.com/watch?v=CCtnNWtC3iA
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Last edited by Corey on Sun May 10, 2015 3:13 am, edited 4 times in total.
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Re: AC Pressure switch - What is it connected to?

Postby Corey » Thu May 07, 2015 5:05 pm

I found the diagram to figure it out.

The two pins which we short on the AC Pressure switch plug to keep the fan system working properly are the two which run between the W3 Water Temp switch and the Rad Fan relay in the engine bay Junction box next to the battery.

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Looks like I can unwrap the portion of the main engine harness next to the AC pressure switch where it runs into the firewall, solder extensions onto those two wires and run them through the fire wall. If I ever get around to this project I'll be sure to post pictures.
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Re: AC Pressure switch - What is it connected to?

Postby underscore » Thu May 07, 2015 5:45 pm

Interesting idea, is the AC button in the cabin maintained or momentary? It's been so long I can't remember.
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Re: AC Pressure switch - What is it connected to?

Postby Corey » Thu May 07, 2015 5:50 pm

Hmm, that's actually a pretty important point. I think its momentary. Not sure how that would work with my scheme. I was going to get a second switch unit from the wrecker and do some artistic modification to the button(s) so it looks like it would control the rad fan, and not the AC.


Here is a picture of the AC switch unit. Its actually two buttons. I was thinking of replacing it with a button like the defrost switch above it.

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Re: AC Pressure switch - What is it connected to?

Postby underscore » Thu May 07, 2015 7:58 pm

Presumably something it's tied to is held (which causes the LED to come on), if you connect to that you should be good to go. I would assume it leads to some of the wiring for the compressor in the engine bay, so you may just need to bridge wires between two plugs in the bay to make this work.
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Re: AC Pressure switch - What is it connected to?

Postby Corey » Fri May 08, 2015 10:56 pm

I have a new, simpler plan for this - I'll make a blocking plate for these two AC buttons and remove the switch assembly. Instead, the car has a disused keyless entry rocker switch on the lower dash. I'll repurpose that for the fan switch.

If I'm feeling ambitious, I may just try this tomorrow.
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Re: How to: AC Pressure Switch Delete

Postby Corey » Sun May 10, 2015 2:59 am

First post of thread updated with the How-to.
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Re: How to: AC Pressure Switch Delete

Postby underscore » Sun May 10, 2015 4:12 am

Nicely done, what's the original function of that switch?
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Re: How to: AC Pressure Switch Delete

Postby Corey » Sun May 10, 2015 4:35 am

From what I have read, it used to switch the keyless entry on and off. When I got the car 8 years ago, I tried to get the keyless entry to work (replaced battery in key, looked up methods to reset etc) but I couldn't figure it out.

When I went on my weight saving binge a few years ago I ended up deleting the keyless entry computer and it's antenna along with the ABS computer (they are next to each other behind the right side door).

So this switch has been sitting in the dash ever since with no purpose.

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Re: How to: AC Pressure Switch Delete

Postby captaingowa » Tue Aug 30, 2016 1:07 am

Corey wrote:When I went on my weight saving binge a few years ago I ended up deleting the keyless entry computer and it's antenna along with the ABS computer (they are next to each other behind the right side door).


So did you remove the ABS pump as well or did you leave that in place?
Because that weighs probably 40 or 50 times the weight of that computer..
Which you would essentially have made the pump dead weight by removing the computer.
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Re: How to: AC Pressure Switch Delete

Postby Corey » Tue Aug 30, 2016 1:51 am

Yep, indeed, an eagle eyed reader would have seen in the engine bay pick above that the pump is indeed removed :wink: . I also removed all the associated wiring from the drivers kick panel all the way to the back of the car. Still need to remove the ABS wiring to the nose of the car.
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Re: How to: AC Pressure Switch Delete

Postby underscore » Tue Aug 30, 2016 5:23 am

On a related note, where did you get that blank plug for where the AC lines used to pass through the firewall?
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Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
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Re: How to: AC Pressure Switch Delete

Postby captaingowa » Tue Aug 30, 2016 2:23 pm

I missed out on the picture because I was looking at your pic of Japanese magazine which lost me..
Now that I am looking, is your air filter tube supporting the fuse box?
The bracket fabrication and welds look really good.
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Re: How to: AC Pressure Switch Delete

Postby Corey » Tue Aug 30, 2016 7:58 pm

underscore wrote:On a related note, where did you get that blank plug for where the AC lines used to pass through the firewall?


Hey, its factory Toyota: part number is 90950-01189

captaingowa wrote:I missed out on the picture because I was looking at your pic of Japanese magazine which lost me..
Now that I am looking, is your air filter tube supporting the fuse box?
The bracket fabrication and welds look really good.


No worries. Yea that japanese book is actually the factory owners manual, pretty cool how its all manga.

Thanks - I designed and cut out the pieces for the bracket/tube, but I had a professional weld it for me.
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