ABC's of 80's Cooling Part III - Press Switch (1 Viewer)

[Ebag333]

I'm planning to wire this up using the rear heater switch (which already has the little fan icon and everything).

It is a 3 position switch and I want it to function as follows
left alone (middle)= auto... turns on/off w/ the AC pressure switch
left (lo)= fan forced on, to cool the truck w/ AC off
right (hi)=fan off (for water xing or parked in hot sun on hot day)

That's an interesting idea, but IMHO you're making it too complex.

If you wire the fan into the pressure switch, then your AC switch already controls the fan. It's then much simpler to wire in a bypass switch to always have the fan on for the rare case (for me at least) where you want the AC off but the fan on.

If you wanted the fan off, just turn off the AC system and wait a minute or so for the system pressure to drop, and the fan turns off.

If you want the AC off and the fan on, flip on your bypass switch.

If you want it operated automatically by the AC system pressure, turn on your AC and have the bypass switch off.

Just my two cents, but in the case of electrical and wiring I very much operate on the KISS principle, and prefer to use as much of Mr. T's wiring/setup as possible.

 

[sandcruiser]

Ebag333: There are two very important things that I don't like about using the AC-on to turn the fan on. #1: after-run. It's hot here. I like the idea of cooling the condenser and radiator after the Cruiser is turned off. #2 (most important): the stock AC will turn off as the car approaches overheating, which would also turn off the fan, which would lead to more heating. That's when I want the fan the most.

Here is what I did. It works.

I found the Fan relay in the under-hood relay/fuse block. For whatever reason, I had a relay in there already... which is what made me continue, but I'm sure that one could find a toyota relay or an aftermarket that would fit the holder.

I jumped 12ga wire from an unused fuse position (also marked "fan" on my fuse box) and added a 20amp fuse.

This is an always-on +12v source. From there I put +12v to 2 positions on the relay -1 and 3, I think but it isn't critical which ones... just so that 1 is the coil and 1 is the switched power.

I then ran 12ga wire forward to the fan from the relay box.
Then grounded the fan to one of the bolts that mounts the horns.

From the last relay pin I ran 2 wires. Green goes forward to the pressure switch, then back to the relay box. White (and the green mentioned before) then go from the relay box to the firewall, below the steering, over to the stock rear heater switch.

At the rear heater switch wiring I cut the Black/Blue wire and the Blue/Yellow wires.
I attached the green wire (from the pressure switch) to the Black/Blue wire. I attached the white wire (directly from the relay) to the Blue/Yellow wire.

Done.

I also spent some time cleaning up PO wiring curiosities. But that's a different story.

The fan now operates exactly as I want.
With the heater switch in the LOW position: The green light on the switch comes on, then when the AC starts up and gets going, a few moments later, the fan kicks in. The fan goes on/off independent of the AC compressor cycles... which makes me think that there might be some (very small) benefit to the motor in that the electrical load is not simultaneous with the AC compressor load.

With the switch in the same position- if I turn the truck off, the green light goes out but the fan will continue to run for a little while. Sitting in full sun this afternoon, it ran for less than 30 seconds after idling w/ AC for 10 minutes or so. Not a great test... but it shows that it does after-run and also stop running. Good.

With the switch in the middle position, the fan doesn't run and no lights are on.

With the switch set to HI, the amber lights up on the switch, the fan runs with the motor running or without, with the AC on, or without. ---- this is the one "danger" setting as it could easily run the battery down if left on. If I get really worried about it, I could install another relay that cuts power to through the green wire whenever the the key is out of the IGN. Or I could just remember to turn it off in the rare instances when I put the fan to "ON" position.

In hot conditions and a slow trail, or when stuck in downtown traffic, I'll plan to leave the fan running pretty much full-time, except when winching, at which point I'll be happy to be able to turn the fan off completely.

The only non-toyota parts used on this mod were about 3 feet of 12ga from the relay to the fan (there might even be wires there in a stock harness), also 3 inches of 12ga from the fuse to the relay. And a few feet (8? 10?) of wire that go from the relay to the px switch, then back to relay, then forward into the cab and over to the stock rear heater switch. And the fuse. Not stock either, but close enough.

Now I just have to re-label the switch, or at least remove the word "rear heater" and "Lo" and "Hi". Anyone know of an icon/two letter symbol for "auto" (ON would be the other label)

Finally: I'm planning to tap into stock rear heater switch wires to potentially control other stuff using rear heater switches.... like reverse lights, for example. As long as you are switching grounds, the system is very easy to modify. And I prefer to switch grounds on relays anyway as it can reduce the number of wires to/from the relay sometimes.

ps: if you find a junked 80, get the rear heater switch. They are pretty versatile. Could also be used to wire driving lights such that they are Off, On, and On with hi-beams. Easy. Or could be used to wire fogs/off/driving for example.

 

[Ebag333]

Ebag333: There are two very important things that I don't like about using the AC-on to turn the fan on. #1: after-run. It's hot here. I like the idea of cooling the condenser and radiator after the Cruiser is turned off. #2 (most important): the stock AC will turn off as the car approaches overheating, which would also turn off the fan, which would lead to more heating. That's when I want the fan the most.

Don't get me wrong, I like your idea. It's just a little too complex for my tastes, and duplicates something that already happens.

For your point number 1....

Hooking it up via the pressure switch means that you get after run until the AC system depressurizes. I don't see how that changes one iota with the way you did it, except that you can disable after run (if you wired it the way I think you did).

For point number 2.....

A bypass switch would force the fan to be on regardless of what the AC is doing. I agree that when the system gets hot enough the AC cuts out, which would then start to depressurize the AC system. You would actually still have an after run effect which would mean that the fan will continue to run even though the AC system is off. You can mimic that simply by turning the AC switch off, and watching the fan continue to run on a hot day. You would get at least a couple of minutes of work otu of the fan.

Again, a simple bypass switch could force the fan to be on regardless of the AC setting.



I'm not trying to knock the way you did things. It's a slick setup, and there are a lot of things I like about it. My only point is that a much simpler setup can mimic everything except disabling the after run. Your setup has the advantage of a single three position switch as opposed to a pair of two position switches.

There's certainly advantages and disadvantages both ways, and your write up provides more options.

 

[sandcruiser]

I didn't think 'your' version through enough before responding

As I understand it, you're saying relay --- px --- ground
with a bypass that goes relay --- sw --- ground

when pressurized, the fan is on.
when switched, the fan is on.

it is simpler.

For me, the added complexity was worth it. But I tend to like options on electrical stuff.
And I live in a hot, humid place where engine over-heating isn't particularly rare... so I do put a premium on being able to run the fan w/o the AC engaged in order to lower the engine temps. But I've never had a problem with the hd-t, so it isn't a particularly high priority function in my real world, so far.

last argument would be: if working on the truck, nice to force-kill the fan to prevent it turning on and eating my fingers. But that is really easily solved by just pulling a fuse.

Mine's niftier ? There. That's it. Mines *niftier*.

 

[Ebag333]

Mine's niftier ? There. That's it. Mines *niftier*.

Agreed. Yours is the pimp version that everyone goes "OH THAT'S SO COOL!" and then never does it.

 

[SUMOTOY]

I didn't think 'your' version through enough before responding

As I understand it, you're saying relay --- px --- ground
with a bypass that goes relay --- sw --- ground

when pressurized, the fan is on.
when switched, the fan is on.

it is simpler.

For me, the added complexity was worth it. But I tend to like options on electrical stuff.
And I live in a hot, humid place where engine over-heating isn't particularly rare... so I do put a premium on being able to run the fan w/o the AC engaged in order to lower the engine temps. But I've never had a problem with the hd-t, so it isn't a particularly high priority function in my real world, so far.

last argument would be: if working on the truck, nice to force-kill the fan to prevent it turning on and eating my fingers. But that is really easily solved by just pulling a fuse.

Mine's niftier ? There. That's it. Mines *niftier*.

No doubt 'niftier' rules. One point to make here though to your theory of operation. The best thing about the pressure switch mod is that if the A/C shuts down from overheat, that is due to too "HIGH" pressure in the system, so the fan will stay on during that time. It didn't appear you understood that clearly.

Not that what you did would change the 'nifty', you just don't need to over-ride the fan when the system is in overheat.

HTH

Scott J
94 FZJ80 Supercharged

 

[sandcruiser]

Scott
thanks for the clarification, that's the way I understood it to work.
the override "ON" would be handy in "running warm, but not overheating" situations like this.

 

[sandcruiser]

another advantage to having an override switch in general:
recently I've found that whenever I return home and wait for the turbo to cool down I like to flip the fan "on" to help cool down the engine a little (and thus speed up the turbo's cooling, a little)

and another advantage to having a fan kill switch: while working on my AC the other day, the technician was charging it... the fan clicked on, he was understandably concerned about that (since he likes his fingers). So I just turned the fan off. All was well. Faster/safer than pulling fuses out.

The same would hold true in a water crossing.

 

[Atoyot1031]

you just don't need to over-ride the fan when the system is in overheat.

I love this mod Scott, but I have found your above statement is false.

This past weekend, when going over four mountain passes while pulling my camper and cranking the AC in ~90 degree weather, the engine got hot enough that the AC kicked out. Guess what? So did the fan.

I had to jump the relay to a solid ground to get it to run constantly. When the temp/pressure dropped, the fan would run by itself again. The fuse didn't blow or anything.

IMHO, a override switch is COMPLETELY NECESSARY to this mod IF you drive in conditions that can cause an overheating situation.

 

[Tools R Us]

...
This past weekend, when going over four mountain passes while pulling my camper and cranking the AC in ~90 degree weather, the engine got hot enough that the AC kicked out. Guess what? So did the fan.

... IF you drive in conditions that can cause an overheating situation.

IMHO the best setup is one where the rig never runs in a overheating situation. With a properly setup belt driven fan and clutch this should never be a problem.

On the N/A rigs it's easy, simply increase the clutch fluid viscosity until it works for your needs. On the S/C rigs it's a bit more of a problem, most setups are crippled/wimpy compared to the N/A setup.

A couple of locals have gone to the 3FE fan, big improvement. Good fan to shroud/radiator spacing and the first time that I have see a S/C rig move air close to a N/A rig!

One just returned from a trip to Illinois and towed a big trailer full of furniture back. The highest temp he saw was climbing a pass in the desert, 206F. On that pass, in the past, most S/C rigs have had heat problems unloaded. His setup is 3FE fan and new type blue hub with 24K fluid, stock thermostat valve adjustment.

A properly setup belt driven fan will be much more powerful than any feasible/cost effective electric. Under some conditions pushers can reduce cooling efficiency, so IMHO improving the belt driven fan is a much better use of resources than playing with wimpy electric fans.

 

[Ebag333]

A couple of locals have gone to the 3FE fan, big improvement. Good fan to shroud/radiator spacing and the first time that I have see a S/C rig move air close to a N/A rig!

What about using the 3FE fan on a N/A rig?

 

[Tools R Us]

What about using the 3FE fan on a N/A rig?

No "need", IMHO the stock 1FZ fan is superior, but can't be used on the S/C rig due to spacing issues.

 

[lndcruz]

Ok, I'm a little confused. Can anyone take a image of what I wire pin 85 into?

 

[Atoyot1031]

IMHO the best setup is one where the rig never runs in a overheating situation. With a properly setup belt driven fan and clutch this should never be a problem.

On the N/A rigs it's easy, simply increase the clutch fluid viscosity until it works for your needs. On the S/C rigs it's a bit more of a problem, most setups are crippled/wimpy compared to the N/A setup.

A couple of locals have gone to the 3FE fan, big improvement. Good fan to shroud/radiator spacing and the first time that I have see a S/C rig move air close to a N/A rig!

One just returned from a trip to Illinois and towed a big trailer full of furniture back. The highest temp he saw was climbing a pass in the desert, 206F. On that pass, in the past, most S/C rigs have had heat problems unloaded. His setup is 3FE fan and new type blue hub with 24K fluid, stock thermostat valve adjustment.

A properly setup belt driven fan will be much more powerful than any feasible/cost effective electric. Under some conditions pushers can reduce cooling efficiency, so IMHO improving the belt driven fan is a much better use of resources than playing with wimpy electric fans.

Kevin, you are preaching to the choir. I have a new blue hub fan clutch that is tuned, 10k'd, and runs a 3.0 fan blade. I also have a 14" pusher fan controlled by the medium pressure switch, hood vents, "cooler" spark plugs, a lower opening temp thermostat, yada, yada, yada. All of these things help to control my temperatures.

However, with a SC'd, bored out motor running a Cruiser that's already loaded down with just about every heavy ass accessory imagineable, while pulling a trailer that weighs over a ton straight up and down the highest passes in the US, the thing gets hot.

My point in the post above is that if you run an electric pusher fan that is controlled via the medium pressure switch, the fan WILL cut out when the AC cuts out. As many people run this setup, I thought it was important to the thread.

In regards to my cooling, I'm open to any ideas. I just think I'm maxing things out, but I hope there is a different solution.

Nick

 

[96r50]

Kevin, you are preaching to the choir. I have a new blue hub fan clutch that is tuned, 10k'd, and runs a 3.0 fan blade. I also have a 14" pusher fan controlled by the medium pressure switch, hood vents, "cooler" spark plugs, a lower opening temp thermostat, yada, yada, yada. All of these things help to control my temperatures.

However, with a SC'd, bored out motor running a Cruiser that's already loaded down with just about every heavy ass accessory imagineable, while pulling a trailer that weighs over a ton straight up and down the highest passes in the US, the thing gets hot.

My point in the post above is that if you run an electric pusher fan that is controlled via the medium pressure switch, the fan WILL cut out when the AC cuts out. As many people run this setup, I thought it was important to the thread.

In regards to my cooling, I'm open to any ideas. I just think I'm maxing things out, but I hope there is a different solution.

Nick

Nick, I'd step up to a 15K cst silicone oil in that fan clutch. I've gone from OEM 3K to 6K, 7K, 10K and now 15K in my new-style blue hub clutch on my N/A truck. I have a few bottles of 20K sitting around too, just in case I want to go higher! I have the valve tuned to about 115F and my coolant temp is pretty solid around 185F.

 

[Atoyot1031]

Heck, I may try 24k as Kevin mentioned above.

In the meantime, I need to install an override switch for the fan. I'd like to wire it so that it turns off with the ignition, but still allows the pressure switch to operate the after run.

Any ideas on how?

 

[Tools R Us]

Kevin, you are preaching to the choir. I have a new blue hub fan clutch that is tuned, 10k'd, and runs a 3.0 fan blade. ....

In our experience, cooling the S/C rig is mostly all about the fan. Under some conditions, the 3.slo ring fan can stall, put out very little air, doesn't matter what clutch. The later "nonring" 3.slo is an improvement, but is a smaller diameter and the shroud fit isn't the best, so somewhat inefficient. The 3FE fan is full diameter, is spaced towards the rear of the clutch, good space to the radiador, is the most efficient that I have seen.

I'm fully convensed that 10K isn't enough in a late type blue hub, for a rig that sees high temps and/or loads. If your running the clutch thermostat set to a lower temp, it's better to set it back close to stock and run thicker fluid. When the thermostat is cheated, you use the the "third step" valve opening for loaded cruising and lose it's use for low speed/idle where the clutch is designed to be the most powerful.

The 3FE fan with 24K fluid is very new, not much data yet, but is looking very promising. The 24K thing maybe a bit much, reported to be a tornado! Hopeing both 3FE fan equiped rig will show at the trail run this weekend, it will be a good comparison with the N/A rigs.

 

[Tools R Us]

Heck, I may try 24k as Kevin mentioned above.

In the meantime, I need to install an override switch for the fan. I'd like to wire it so that it turns off with the ignition, but still allows the pressure switch to operate the after run.

Any ideas on how?

The simple way would be to wire the switch to ground/power (which ever the circuit uses) the relay and close it. This may back feed in to the trigger circuit causing unintended results. The best way would be to run separate parallel relays, so ether/both can run the fan.

 

[Atoyot1031]

In our experience, cooling the S/C rig is mostly all about the fan. Under some conditions, the 3.slo ring fan can stall, put out very little air, doesn't matter what clutch. The later "nonring" 3.slo is an improvement, but is a smaller diameter and the shroud fit isn't the best, so somewhat inefficient. The 3FE fan is full diameter, is spaced towards the rear of the clutch, good space to the radiador, is the most efficient that I have seen.

I'm fully convensed that 10K isn't enough in a late type blue hub, for a rig that sees high temps and/or loads. If your running the clutch thermostat set to a lower temp, it's better to set it back close to stock and run thicker fluid. When the thermostat is cheated, you use the the "third step" valve opening for loaded cruising and lose it's use for low speed/idle where the clutch is designed to be the most powerful.

The 3FE fan with 24K fluid is very new, not much data yet, but is looking very promising. The 24K thing maybe a bit much, reported to be a tornado! Hopeing both 3FE fan equiped rig will show at the trail run this weekend, it will be a good comparison with the N/A rigs.

Which 3FE fan? (are all models and years the same?)

FYI, I now have no problems at all on trail rides. It's only pulling the camper at highway speeds, with the hammer down so I can maintainas much speed as possible, which the Cruiser does quite well considering the load and turning 37s.

 

[sandcruiser]

let's not forget an added benefit to the Aux fan, if installed "well"--- your fan can continue to run after you shut down the rig.

While this may or may not seem important, if you shut the rig off for a few minutes (say, to get fuel) and have after-run enabled, it seems to make for a colder AC when you start up again. I like that.

Also, my 60 used to regularly belch a little fluid if we shut it down after driving it hard. There may have been many different reasons. But I'm pretty sure that in most rigs, the radiator gets hotter right after you stop. Dumping some of that heat out can only be a good thing, in my opinion.

and moving air out from the engine compartment is probably also good for other components, like the motor, the turbo (or supercharger) and whatever else doesn't want to get over heated (brakes fluid?, I don't know...)

also: I tore the switch open a little while ago because it had minor issues with the "hi" window falling into the switch. It is easy to tear a rear heater switch apart. Just in case someone wants to do it.
I ended up using a sharpie market to black out the word "rear" on the switch, so now it just shows a fan, which is a little bit niftier than it was before.