ABC's of 80's Cooling Part III - Press Switch (3 Viewers)

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Ok, my question here is can you wire up the relay WITH the pressure switch and also manually controll the fan ON and OFF also with a 2 way switch by grounding or powering pin 85 or 86. I got all the parts however after reading through the threads im starting to brain fart. So essentially i can interrupt the ground and controll it via switch to manually turn it on and off?

Below is taken from Sumotoys thread.

3) Since this is a ground circuit, the wires have no 'polarity'. Take one of the leads and attach it to pin 86 (activation ground) on the relay. Take the other lead and attach it to chassis ground.

4) For manual override, you can piggyback another wire to pin 86 to switch in cab, then to ground.

5) Done
 
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sure, obviously there are a few ways of doing this. I just ran a second wire from the CDS circuit ground and stashed it behind the DS kick panel until i figured out what switch i wanted to use. this will turn the fan on when grounded. to turn it off i figure i can all ways pull the CDS fuse.

The pressure switch has two wires, one to ground and the other to the ground side of the CDS control relay. Add a second wire to the ground side of the control relay and add a manual switch to ground. or in my case, leave that wire in the kick panel for later switch install or emergencies.

After a summer with this mod i love the after run, blows cold much faster after short stops and works great at traffic lights. I even used the above mentioned wire once when my truck was running hot, pulled it out and wrapped it around a door pin. Not sure it did much but couldn't have hurt. Great mod in my opinion, put in the OEM relay and fuse bits, I did. Heck its all ready labeled for it:cheers:
 
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Just finished doing this to my 80. Works like a champ. I used a '90s 4runner fan. For being so small, it moves a lot of air. It's supposed to be back in the 90s later this week. I will report back on a/c performance then. My goal is to improve a/c cooling in heavy traffic (ie idling along in stop and go traffic).
 
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Success. Sitting at a long light, ambient temp was 95f and the AC was holding at 40f. Before it would creep up to 45ish and start cutting the compressor out because the high side switch was maxing out. I have it wired so that I can control the fan manually. I would flip it on when my road speed was less that 35mph. I will go back once I get some wire terminals and wire it into the pressure switch so that it's automatic.
 
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Around here, this is a well proven way to kill batteries. When setting in the sun or even in a garage, the heat drives the pressure up, fan comes on, repeat. Almost went crazy attempting to find the draw, finally figured it out. Easy fix, simply hook the trigger to the clutch, the fan comes on with the A/C, works great, no more issue. Better yet, properly tune the clutch, in most cases, makes the electric thingy redundant, useless. :hillbilly:
 
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Around here, this is a well proven way to kill batteries. When setting in the sun or even in a garage, the heat drives the pressure up, fan comes on, repeat. Almost went crazy attempting to find the draw, finally figured it out. Easy fix, simply hook the trigger to the clutch, the fan comes on with the A/C, works great, no more issue. Better yet, properly tune the clutch, in most cases, makes the electric thingy redundant, useless. :hillbilly:

Wire it to a keyed source.
 

Will Van

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Here is a wiring diagram for the electrically inept, like me.

Auxiliary_Fan_Pressure_Switch_Wiring_Diagram.jpg
 
Joined
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Ivins UT
Curious if this works on a 91 3FE FJ80. Is this the pressure switch mentioned in the op?

IMG_5387.jpeg


EDIT: Yes, this is the pressure switch noted in the OP. Described in the FSM:

IMG_5401.jpeg
 
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1993 Land Cruiser
Does anyone know what the part number for the CDS relay that fits in the relay box that is under the hood? I would love to put the relay there for a super clean install. Thanks!!!

View attachment 1940483

Looks like its 90987-02004, and my relay box lists it as a 20Amp fuse.

Located on this parts diagram:

 
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I think I liked @NLXTACY thread better :flipoff2:

Supposed to be 95* today here, keep those 80's cool ;)

Trying to track down a PN for a 9098702004 4 pin denso relay connector (or Socket terminal?).

Screen Shot 2020-06-22 at 1.22.23 PM.png


Also, is there an OEM PN for a fuse connector plug/lead? that would be the other piece of the puzzle.

UPDATE:
Fusebox Blade Fuse Contacts - 82998-12140
Fusebox Relay Contacts - 82998-12060

via:

 
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FWIW I just did this a took a few pics. Hopefully it helps.

Here is the sensor location behind the drivers headlight.
View attachment 2393875

The connector on the harness has provisions for 4 pins, but only two are used. The sensor has 4 pins. Two are blocked with rubber plugs. In order to install the new terminals, the white retainer needs to be popped straight up. It doesn’t come out.
View attachment 2393878

I have an old wiring harness that i scavenged the terminals from, but now you can wire the relay to the sensor.
View attachment 2393876

On the relay, pin 30 and pin 85 are tied together and go to a fused always on battery source. Pin 87 goes to the positive fan lead, and pin 86 goes to one of the new pressure sensor pins you wired in. It doesn’t matter which one.
Now you tie the other pressure sensor wire and the negative fan lead together and ground to chassis.
 
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Did this today. Took a few hours, and a bunch of electrical parts/tools, plus the oem stuff.

summary of my build:

oem fan
oem fuse box install with oem relay
triggered on ground side of relay to high pressure ac switch.
Cabin switch override (can turn on, but can’t turn off if ac pressure is high. Figured it would be nice to be able to push more air if desired).

everything works, except the ac pressure high switch isn’t turning off after drive 2 miles.

ambient temp today is 110 in s.utah and looking at numbers it looks like threshold for the pressure switch is about 115? Yeah this thing isn’t going to turn off for a long while.

i let it run for 10 mins then pulled the fuse. Looks like I need to maybe switch the high pressure switch instead of a force on switch.

throwing the fuse back in after and hour and the thing is still on. Granted, fan wasn’t running, but who knows how long it would take. Engine is hot and it’s sitting out in the sun.

So I guess the plan now is to run the high pressure switch in series instead of parallel with the cabin switch. That way I can override the afterrun fan if it’s hot as hell out, but leave it on in normal temperatures.

A couple of other notes:

- Relay gets too hot to touch. Normal? 20A fuse.
- The led on the switch isn’t turning on. Maybe it’s designed to hoop up the other way.
- high pressure switch started off today. But just a short time brining the car up to temp, I’m getting zero shutoff on a hot day in the sun.
- the electric fan does push a lot of air.
- gonna look into the fan clutch mod
- hood vents would be cool too.
 
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Oh. One last thing:

PO mentioned they recharged the ac system relatively recently. Didn’t say what kind of gas or who did it, but I wouldn’t be surprised if it was a can from the local parts store.

could the PO refilling the system with the wrong pressure or amount of refrigerant affect the behavior of the pressure switch? I imagine so.

thinking it would be worth ensuring a professional recharge the system correctly.
 

flintknapper

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Oh. One last thing:

PO mentioned they recharged the ac system relatively recently. Didn’t say what kind of gas or who did it, but I wouldn’t be surprised if it was a can from the local parts store.

could the PO refilling the system with the wrong pressure or amount of refrigerant affect the behavior of the pressure switch? I imagine so.

thinking it would be worth ensuring a professional recharge the system correctly.

Overcharging the system could result in higher than normal pressures, but this would not affect the operation of the Binary/Trinary switch, it will still cut in and out at the designed pressures if that is your question.

For peace of mind....you might want to have the system evacuated and the proper amount of refrigerant 'weighed in'.
This insures you don't have too much or too little. You can use a set of manifold gauges to check the high and low side pressures (relative to the ambient temp) but....it will only show you IF the pressures are within an acceptable 'window'.

The trouble with that method however is that moisture, air or too much oil can create an artificially high pressure reading, resulting in diminished A/C performance despite being what you think is the correct pressure. Anytime you purchase a used vehicle you can expect the health of the A/C system to virtually be an unknown (lacking full service records).
 
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Another 100+F hot day, but only drove around the block (~5 mins) with the AC on for a couple mins. The medium pressure switch kicks on immediately when you turn the AC on and seems to just stay on for a long time, way longer than the 30 seconds to 5 minutes people are reporting here. Running a 91 that I believe was converted to the newer gas years ago.

Curious to try in colder weather but then also you dont need AC in colder weather.

The mod I did today was to run the pressure switch in series with a cabin switch. The switch illuminates when the pressure switch is active (indicator if the fan will run in on mode or not), and the switch as an on/off override for the fan, since the after run isn't working the way I wish it were.

Worst case scenario, I can just take the pressure switch out and have a cabin controlled fan.
 

KennyBob

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Another 100+F hot day, but only drove around the block (~5 mins) with the AC on for a couple mins. The medium pressure switch kicks on immediately when you turn the AC on and seems to just stay on for a long time, way longer than the 30 seconds to 5 minutes people are reporting here. Running a 91 that I believe was converted to the newer gas years ago.

Curious to try in colder weather but then also you dont need AC in colder weather.

The mod I did today was to run the pressure switch in series with a cabin switch. The switch illuminates when the pressure switch is active (indicator if the fan will run in on mode or not), and the switch as an on/off override for the fan, since the after run isn't working the way I wish it were.

Worst case scenario, I can just take the pressure switch out and have a cabin controlled fan.

Interesting. I'm definitely experiencing the short run duration after I shut my engine off. I believe my setup is the same minus the manual switch.
 

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