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Old 05-02-2011, 08:26 PM
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Need Some Wiring Help Please

Hey guys I just switched over to an electric fan and ive figured out how to wire it all up but cant figure something out.

As most fans are it has 2 wires coming out, 1 positive, 1 negative. What I want to happen is have the fan turn on whenever the temp sensor tells it to and ALSO have it run ALWAYS when the a/c is on.

If anyone has a schematic that would be awesome. Thanks a million.
-Steve

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Old 05-02-2011, 10:42 PM
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what kind of car we talking about?

Use a relay to supply power to the fan. Connect the negative side of the relay coil to temp sensor. When the engine temp reaches the sensors closing temp, it will provide the ground to complete the circuit through the relay coil energizing the relay, turning the fan on.

For AC request, find the wire on the control side of the AC high pressure switch. On some GMs it's on the dryer/accumulator. Tap into this wire to another relay to provide the ground for the above relay. Make sure you are on the control side of the AC high pressure switch or the fans will cycle with the compressor, which is what you don't want.
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Old 05-02-2011, 11:55 PM
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after much research this is what I was able to compile for my project. This is a 59 chevy truck and I am trying to put the electric fan on it.

RELAY:
pin 86-toggle switch in car AND temp switch
pin 87-positive of fan motor
pin 87a-not used
pin 85-ignition power (only on when key is on)
pin 30-constant power from battery

for some reason one diagram I found had 85-30 tied together to constant battery power...anyone know why that is? Is the above setup I have correct? As for the a/c this is a sure-fit vintage air kit. Youre saying I should tap into the negative wire on the pressure switch and connect that to pin 86 as well?

If this is not correct any schematic or pin diagram similar to above would be perfect.

Last edited by chevyrestore; 05-03-2011 at 12:02 AM.
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Old 05-03-2011, 05:50 AM
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DeRale makes a fan relay kit that has the relays, a thermostat probe and adjustable thermostatic control, A/C input, and an input for a manual 'on' switch, about $40.
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Old 05-03-2011, 06:38 AM
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Quote:
Originally Posted by chevyrestore
after much research this is what I was able to compile for my project. This is a 59 chevy truck and I am trying to put the electric fan on it.

RELAY:
pin 86-toggle switch in car AND temp switch
pin 87-positive of fan motor
pin 87a-not used
pin 85-ignition power (only on when key is on)
pin 30-constant power from battery

for some reason one diagram I found had 85-30 tied together to constant battery power...anyone know why that is? Is the above setup I have correct? As for the a/c this is a sure-fit vintage air kit. Youre saying I should tap into the negative wire on the pressure switch and connect that to pin 86 as well?

If this is not correct any schematic or pin diagram similar to above would be perfect.
Not sure what you are doing with the toggle switch on 86, but yes that will work. Connecting 85&30 to constant battery power will allow your fans to run when the key is off till the sensor cools down and opens. I personally would not do it that way, but suit yourself.

I don't know how Vintage air wires their stuff, but it may be a 12V+ wire going to the pressure switch. Check it, if it's 12V+ you will need to use another relay as I posted above.

Several companies make fan controllers as Cucumber has posted. Two relays and a bit of wiring is way cheaper, but the fan controllers are easy.

I have attached a schematic of how I did one on our S10. I used a fixed sensor for one fan and an adjustable fan controller for the other fan. It works well, probably overkill, but trouble free fan operation.
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Old 05-03-2011, 08:58 AM
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Here's another option that is simpler, but a bit more expensive. You can replace your pressure switch with a trinary switch, which does everything the pressure switch does plus has a separate switch in it that that triggers the rad fan to come on at a certain refrigerant pressure. Here's a diagram of how I usually do it:



Note: Some radiator fans draw more amps than others. This diagram applies to common fans (such as Spal) that draws less than 20 amps. Fans that draw more would require a bigger circuit breaker, larger wires, and higher rated relays (sometimes dual relays).


Hope this helps.....
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Old 05-03-2011, 09:27 AM
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if it's a vintage air unit:
you should have a trinary switch installed to protect the system from low & high pressures
it also has a lead for fan on
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Old 05-03-2011, 03:11 PM
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that last schematic is exactly what I want. I pulled up the schematic for the a/c kit and there is no Trinary switch...there is a Binary switch in line that has a wire from the a/c thermostat next to the blower motor going into the binary switch and then out of the switch to the compressor. The wire going to the compressor is 12v+ when running and 0v when not running. Since that last schematic had the a/c on the ground side am I going to need a second relay to make it work or how should I do that?
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Old 05-03-2011, 03:48 PM
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Quote:
Originally Posted by chevyrestore
that last schematic is exactly what I want. I pulled up the schematic for the a/c kit and there is no Trinary switch...there is a Binary switch in line that has a wire from the a/c thermostat next to the blower motor going into the binary switch and then out of the switch to the compressor....
The diagram I posted is assuming you use a trinary switch instead of a binary switch. A trinary does everything a binary does PLUS it also controls the radiator fan based on refrigerant pressure. A trinary switch looks like this:



Here is a link to the trinary switch wiring diagram on the Vintage Air website:
Vintage Air Trinary Switch

Quote:
....The wire going to the compressor is 12v+ when running and 0v when not running. Since that last schematic had the a/c on the ground side am I going to need a second relay to make it work or how should I do that?
If you do not use a trinary switch and just have the fan run all the time the AC is on, then yes, you would need another relay to change the positive signal from the AC thermostat to to a ground signal for the fan relay, just like Overdriv said before.

Hope this helps....
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Old 05-03-2011, 05:25 PM
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Great thanks...since the signal at the compressor will go and off should I avoid that wire and put a relay on the wire that only has power with the ac on at the blower motor speed switch? Any ideas appreciated. Can someone also display how to run that second relay in the wiring schematic above? I don't want the fans to go on and off with the magnetic clutch.
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Old 05-03-2011, 06:22 PM
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Quote:
Originally Posted by chevyrestore
Great thanks...since the signal at the compressor will go and off should I avoid that wire and put a relay on the wire that only has power with the ac on at the blower motor speed switch? Any ideas appreciated. Can someone also display how to run that second relay in the wiring schematic above? I don't want the fans to go on and off with the magnetic clutch.
You would probably want to tap into the wire between the binary switch and the AC Thermostat to trip the additional 'AC Request' relay. Like so:


(please pardon my hastily drawn diagram)

Good luck.....
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Old 05-03-2011, 06:57 PM
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Quote:
Originally Posted by chevyrestore
Great thanks...since the signal at the compressor will go and off should I avoid that wire and put a relay on the wire that only has power with the ac on at the blower motor speed switch? Any ideas appreciated. Can someone also display how to run that second relay in the wiring schematic above? I don't want the fans to go on and off with the magnetic clutch.
On the attached schematic the AC request 12V+ will be the wire from your AC controls that sends 12V+to the pressure switch, then from there it will go to the compressor clutch. If you connect to the wire that is coming from the AC controls it will be 12V+ any time AC is selected. If you use the wire from the pressure switch to the compressor, the fan will cycle with the compressor.

If you have a pressure switch which supplies a ground during AC request, then obviously you will not need the second relay.

The first schematic I posted was not meant as the way you should wire your fan, only to show you how to use a relay to provide a ground.

Hope this helps, good luck.
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Old 05-03-2011, 08:16 PM
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do I need to use a circuit breaker or could I use a 30amp fusible link? Just wondering why a circuit breaker is being recommended when they arent as common as the fusible links.
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Old 05-03-2011, 10:23 PM
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Quote:
Originally Posted by chevyrestore
do I need to use a circuit breaker or could I use a 30amp fusible link? Just wondering why a circuit breaker is being recommended when they arent as common as the fusible links.
Personally I'd rather use a circuit breaker. It will reset after the load has been removed. A fusible link uses a smaller gauge wire as a sacrificial element that once it's opened it will need to be replaced.

Use what you feel comfortable using. Both will protect your wiring and devices.
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Old 05-03-2011, 11:04 PM
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awesome thanks for the info. Ive got everything wired up minus the a/c relay setup because I ran out of wire The fans are supposed to be here tomorrow afternoon from Fedex so ill give it a go and let you guys know how it went. Thanks so far!
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