Part III - Pressure Switch Activation of Aux Fan for better A/C Condenser Cooling.
In Part II, you will find the relay trigger options for wiring the pusher Aux fan for maximizing A/C condenser efficiency. In Part III, I will detail the procedure for wiring the Aux Fan to come on using the A/C Condenser Pressure switch. Luckily for the Toyota purists this uses only 10 dollars worth of Toyota Parts.
By now, you should have the Aux pusher Fan mounted in front of the A/C condenser, a relay mounted, and your Battery Feed (with appropriate Fan Fuse please!) to pin 30, and the Fan Positive Wire to Pin 87, Fan negative wire grounded to chassis. You can hook pin 85 (12+ relay trigger - low amp) to either switched power or directly to battery power (what I prefer for after-run). That should leave only Pin 86 (relay activation ground) not connected.
rinthe Aux Fan for Maximum Performance
To recap Part I& II I identified the need for some low rpm/low vehicle speed condenser cooling, and installed an aux fan. Now for fan activation... Most folks that have done this modification have tapped into the compressor 12v+ line. The problem I see with that is when the A/C compressor is shut off from an overheat situation (108C - 226F engine temps) you also lose the aux fan cooling when you need it the most. It can also lead to a massive drop in idle rpm (stall even), since you are adding compressor *and* fan amp load at the same instant. Thankfully Toyota made the solution cheap and easy. There is an unused pressure circuit already in the A/C high pressure switch.
When I replaced my factory hi/lo pressure switch 886450-01080, I noticed both the old and new had 4 pins, and the plug only had 2 wires. The FSM lists 2 pressure circuits for this switch: Hi/low in series, and a Medium Pressure switch. But, they only use the hi and the lo series circuit, which leaves a great Factory aux fan activation circuit ready to install.
The Pressure Switch works as follows:
Hi Pressure circuit - off - no continuity = 412psi (A/C Compressor off)(Aux Fan = on)
Hi pressure circuit - on - continuity = 327psi (A/C Compressor on)(Aux Fan = on)
Lo pressure circuit - off - no continuity = 30psi (A/C Compressor off)(Aux Fan = off)
Lo pressure circuit - on - continuity= 33psi (A/C Compressor on)(Aux Fan = on)
MED pressure circuit - on - conitnuity = 192psi (Aux Fan on)
MED pressure circuit - off - no continuity = 156 (Aux Fan off)
continuity = completed circuit
no continuity = interrupted circuit
So, tapping aux fan relay ground into the unused medium pressure will allow aux fan activation at 192psi>. Which means exactly that if high pressure cutout switch is triggered, the fan is still running. It also means when A/C is switched off all together, the fan will drop the condenser down to 156psi, and shut off.
This also acts as an afterrun cooling circuit, since you can use battery power to the relay, not any other switched power. Run the truck to the store, shut it down, the fan runs until the high presssure is down to 156psi, then shuts off (10seconds - 3 minutes depending on how hot the condenser is). Come back out, start the truck, turn on the A/C, instant cold. Ok, now the skinny on the procedure for pin 86 routing (this is a ground circuit!)
1) You need only 2 parts from the dealer (mine had them in stock)
QTY 2 x 82998-12270 Terminal = 10.oo for the pair
These are 2 precrimped and short lead terminals with weather plugs attached that will plug into the unused Med pressure ports in the hi/low pressure switch plug at near the site glass.
2)Remove the switch plug. On the back you will see two wires going into the switch plug. On the 2 unused round holes you will see two black rubber plugs, remove those (I pushed them from the terminal side out the wire side with a small piece of wire), they are just pressed in.
2) Now from the back of the plug, you will insert the 2 leads into the holes in the plug. STOP. Make sure that the retaining clip divot (the indentation about half way down the silver terminal) is located to the ouside of the switch plug. That's where the retaining clips for the terminal is molded into the switch plug. Push these into the clip and make sure the orange water plug on the terminal is sealed into the back of the switch plug. Plug the switch plug back into the high pressure switch.
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
This will activate the Aux Fan on A/C startup after the condenser has reached 192psi and will stay on until condenser pressure reaches 156psi (130F and 115F respectively)
I have been running mine with the afterrun feature to reduce the temps on shutdown, and the fan runs about 1-2min after engine turns off, then shuts off.
Next up - Getting heat out of under the hood
Scott Justusson
QSHIPQ Performance Tuning
Chicago
94 FZJ80 Supercharged
In Part II, you will find the relay trigger options for wiring the pusher Aux fan for maximizing A/C condenser efficiency. In Part III, I will detail the procedure for wiring the Aux Fan to come on using the A/C Condenser Pressure switch. Luckily for the Toyota purists this uses only 10 dollars worth of Toyota Parts.
By now, you should have the Aux pusher Fan mounted in front of the A/C condenser, a relay mounted, and your Battery Feed (with appropriate Fan Fuse please!) to pin 30, and the Fan Positive Wire to Pin 87, Fan negative wire grounded to chassis. You can hook pin 85 (12+ relay trigger - low amp) to either switched power or directly to battery power (what I prefer for after-run). That should leave only Pin 86 (relay activation ground) not connected.
rinthe Aux Fan for Maximum Performance
To recap Part I& II I identified the need for some low rpm/low vehicle speed condenser cooling, and installed an aux fan. Now for fan activation... Most folks that have done this modification have tapped into the compressor 12v+ line. The problem I see with that is when the A/C compressor is shut off from an overheat situation (108C - 226F engine temps) you also lose the aux fan cooling when you need it the most. It can also lead to a massive drop in idle rpm (stall even), since you are adding compressor *and* fan amp load at the same instant. Thankfully Toyota made the solution cheap and easy. There is an unused pressure circuit already in the A/C high pressure switch.
When I replaced my factory hi/lo pressure switch 886450-01080, I noticed both the old and new had 4 pins, and the plug only had 2 wires. The FSM lists 2 pressure circuits for this switch: Hi/low in series, and a Medium Pressure switch. But, they only use the hi and the lo series circuit, which leaves a great Factory aux fan activation circuit ready to install.
The Pressure Switch works as follows:
Hi Pressure circuit - off - no continuity = 412psi (A/C Compressor off)(Aux Fan = on)
Hi pressure circuit - on - continuity = 327psi (A/C Compressor on)(Aux Fan = on)
Lo pressure circuit - off - no continuity = 30psi (A/C Compressor off)(Aux Fan = off)
Lo pressure circuit - on - continuity= 33psi (A/C Compressor on)(Aux Fan = on)
MED pressure circuit - on - conitnuity = 192psi (Aux Fan on)
MED pressure circuit - off - no continuity = 156 (Aux Fan off)
continuity = completed circuit
no continuity = interrupted circuit
So, tapping aux fan relay ground into the unused medium pressure will allow aux fan activation at 192psi>. Which means exactly that if high pressure cutout switch is triggered, the fan is still running. It also means when A/C is switched off all together, the fan will drop the condenser down to 156psi, and shut off.
This also acts as an afterrun cooling circuit, since you can use battery power to the relay, not any other switched power. Run the truck to the store, shut it down, the fan runs until the high presssure is down to 156psi, then shuts off (10seconds - 3 minutes depending on how hot the condenser is). Come back out, start the truck, turn on the A/C, instant cold. Ok, now the skinny on the procedure for pin 86 routing (this is a ground circuit!)
1) You need only 2 parts from the dealer (mine had them in stock)
QTY 2 x 82998-12270 Terminal = 10.oo for the pair
These are 2 precrimped and short lead terminals with weather plugs attached that will plug into the unused Med pressure ports in the hi/low pressure switch plug at near the site glass.
2)Remove the switch plug. On the back you will see two wires going into the switch plug. On the 2 unused round holes you will see two black rubber plugs, remove those (I pushed them from the terminal side out the wire side with a small piece of wire), they are just pressed in.
2) Now from the back of the plug, you will insert the 2 leads into the holes in the plug. STOP. Make sure that the retaining clip divot (the indentation about half way down the silver terminal) is located to the ouside of the switch plug. That's where the retaining clips for the terminal is molded into the switch plug. Push these into the clip and make sure the orange water plug on the terminal is sealed into the back of the switch plug. Plug the switch plug back into the high pressure switch.
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
This will activate the Aux Fan on A/C startup after the condenser has reached 192psi and will stay on until condenser pressure reaches 156psi (130F and 115F respectively)
I have been running mine with the afterrun feature to reduce the temps on shutdown, and the fan runs about 1-2min after engine turns off, then shuts off.
Next up - Getting heat out of under the hood
Scott Justusson
QSHIPQ Performance Tuning
Chicago
94 FZJ80 Supercharged
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