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View Full Version : Radiator fan Hooked to AC button?



BlueDragon
06-29-2010, 04:46 PM
Wondering if anyone has done or thought of using the AC switch to turn on a radiator fan? I have removed the AC and my wiring or something has shorted for my fan. Just wondering if anyone knows what wire would be hot when the AC button is turned on or if it even works like that... Just wondering... seems like a cool mod and it would keep me from adding another tacky looking toggle switch.

Tecker184
06-29-2010, 05:22 PM
I was thinking the same thing but for my heat exchanger fans. I too would like to know if this would work.

pinoyGT4
06-29-2010, 08:31 PM
it could..

my uncle wired two rad fans to his rear windshield wiper switch on the lever on the steering column.. :D

anyway thats a custom made jeep.. but yeah, i guess its doable.. :D

BlueDragon
06-29-2010, 08:46 PM
would we need to just use it to trigger a relay or would it provide the amps we need to run a stock fan? anyone have experience?

Hipster Lawrence
06-29-2010, 11:50 PM
This is a terrible idea. What's wrong with doing it the right way?

Wiring the cooling fans to a switch is a great way to blow a head gasket. If you must hack up the factory system just wire them to be on all the time just be prepared to replace the fans when they burn up.

Hookecho
06-30-2010, 01:04 AM
as long as you monitor the temp gauge and turn the fans on when in stop and go traffic you'll be fine. it's only a stupid idea if you yourself are stupid and don't pay attention to your gauges.

their should be a harness that used to plug into your a/c compressor. one of those wires should be the 12v one for tha a/c switch. there should also be a ground wire.

85gtsblackman
06-30-2010, 05:02 AM
i know on the 5th gens i had i just unplugged the fan thermostat sensor on the bottom of the radiator and the fans ran constant, never had em die in 3+ years worth of time, just sayin....


or you could get an aftermarket fan wiring set up with an adjustible thermostat and the sensor is a probe that sticks in the radiator

pinoyGT4
06-30-2010, 08:11 AM
This is a terrible idea. What's wrong with doing it the right way?

Wiring the cooling fans to a switch is a great way to blow a head gasket. If you must hack up the factory system just wire them to be on all the time just be prepared to replace the fans when they burn up.

true..

my thermoswitch was busted for sometime and i had the fan on all the time..

i blew my head gasket when i overheated while on a highway coz the fan motor burned..:nopity:

85gtsblackman
06-30-2010, 09:21 AM
shoulda ran the heater

klapa
06-30-2010, 02:27 PM
As far as I can tell - from the wiring diagram for my fifth gen - the radiator fan relay coil path to ground does go through a normally closed contact of the A/C pressure switch.

I would think if A/C has been removed - you could just jump that connection around the A/C pressure switch and still use the water temp sensor and the rest of the circuitry for radiator fan control.

As far as I can tell - from the wiring diagram for my fifth gen - the radiator fan relay coil path to ground does go through a normally closed contact of the A/C pressure switch.

I would think if A/C has been removed - you could just jump that connection around the A/C pressure switch and still use the water temp sensor and the rest of the circuitry for radiator fan control.

Hipster Lawrence
06-30-2010, 05:16 PM
it's only a stupid idea if you yourself are stupid and don't pay attention to your gauges.




Well you just described 99% of the people in the world.

I myself pay attention to the road not my gauges. Idiot lights are there for a reason, gauges are cool and all but most people won't notice a pegged gauge until it's too late. Thats why you don't see a bunch of gauges on an f1 car or most other all out race cars you see idiot lights. If there are gauges they will almost always be combined with a light.


Edit,

On most cars the coolant temp sensor is located in a water outlet somewhere near the head and the fan switch is in or close to the radiator. This is because the thermostat regulates the engine temp and the fans just take heat away from the radiator. So if you are just looking at the gauge on the dash you may be being misled a bit as to the temperature in the radiator.

Tecker184
06-30-2010, 05:17 PM
So what would have to be jumped? I want to do this for my W2A heat exchanger fans. I tried to figure it out but those wire diagrams give me a head ache.

BlueDragon
06-30-2010, 09:36 PM
well that sounds like the answer to my problem right there... I had the engine and tranny out to do all the seals and metal head gasket removing the AC and clocking and re-routing my ic piping and the clutch etc yadda yadda... anyways I have had trouble with this not working since I put it all back in, maybe if you can tell me which wires to jump together the whole system will work again... I even bought a new temp sensor for the radiator... would be nice to have it all work stock again and maybe just run my extra radiator fan off the AC switch.
Thank you for the info and all of you for responses.

BlueDragon
07-04-2010, 05:18 PM
well I jumped the pressure switch with no result. I have looked over the wiring diagrams but I am much too novice in this area to figure out what is wrong. Also the Big Green Book does not have wiring for Alltrac only 5sfe so I am not sure if it is the same or what. Anyone else removed their AC before and had this happen??

klapa
07-04-2010, 06:51 PM
Well - I have a '91 alltrac myself - and have just been through allot of stuff with my '92 5sfe GT trying to get the AC running.

I compared allot of stuff in my alltrac while I was trying to figure some stuff out and it all really seems to be the same between the two - except the trac has the "automatic" A/C (has a thermostat on the dash) while the GT has the "manual" (just A/C on off and fan speed control).

I had mistakenly been using the "automatic" diagram for my GT because I thought it was "automatic trans" lol. So I have that right in front of me now as I printed it with my company color printer. Not sure if the term numbers will agree with your trac or not, but here's what I see:

One of the A/C condenser fan relays (there are three) and the rad fan relay coils get their ground through the A/C pressure switch and also finally the water temp switch. There is a "check" connector between the real coil negative and the water temp switch - this should have a light blue wire with black tracer. Grounding one side of this one wire connector would test your cooling fan relay.

Looking through the very "spartan" explanation of the system operation I'm trying to figure out how the A/C and cooling fan control is related - while I'm an electronic engineer I can tell you that 93celicaconv knows allot more about it than I do.

I'm interested in this - so will go through the diagram and see if I can figure it out.

I also have both a '92 GT 5sfe with the "manual A/C" and a '91 alltrac with the "automatic" A/C so can make some comparisons as to wire colors and terminal numbers, etc.

I'll wait and see if 93CelicaConv chimes in - as he might know the answer right off the top of his head.

I'm cleaning out the garage today so will check back on this from time to time during my "beer breaks".

klapa
07-05-2010, 02:31 PM
I read through the description of the "automatic" system and can't really see anything that would cause the fan NOT o come on - so long as the radiator fan relay #1 is good and the rad temp switch is good the fan should come on if you jumped the pressure switch contacts.

The rad fan can be controlled by the A/C fan relays 2 and 3 - but as far as I can tell that should only happen when you have the A/C switch on. In that case it seems that both the rad fan and condenser fan are controlled by those two relays - in one case the fans are fed in series to cause them to run at low speed and the other they are fed in parallel for high speed.

There are actually three A/C pressure switches - two are in series that go to the A/C amplifier and the other is the contact for the fan. Make sure you are jumpering the right one - for the diagram I'm looking at that should be Light Green/Black wire and Light Blue/Black wires. Pins 2 and 3 of the pressure switch connector A5.

BlueDragon
07-15-2010, 03:55 PM
Thank you for the info Klapa. I was still unable to get it to work. The condenser and fan are removed also so I am not sure if that has something to do with it all. It seems there are 3 relays and as many switches just for this one thing... its just too much for me to figure out alone, maybe when my buddy with my old AT gets back in town from Costa Rica I can try again...

But for now I just hooked up a relay to be turned on by a switch that gets power when the car is on.
I still would however like to hook up my Aux fan incase of failure or just wanting to keep it cool on a high boost drive.

So from what I can see I should try to find the 12V live wire running down to the compressor plug and use it to switch on another relay for the other fan?? I would assume I do not want to draw the current used for the fan from that wire correct?