Hey folks, I've been chatting with a few people and decided to see what the majority has to say here!

I am going to put one of those Mark 8 fans on my truck, a two speed one. I think I know how i want to wire this, but basically I want the low speed to be used for temp control and the high speed to be used with the A/C compressor.

I know these fans draw a large amperage on start up (close to 100A one said) and then when running use approx 30-35amps.

Any tips for me? Also I plan to follow this diagram, but in order to do this, because this is a two speed fan, I am going to have to disable the low speed temp relay in order to use the high speed A/C relay. SO I'd have to install a switch somewhere in the low speed circuit.

http://www.geocities.com/smithmonte/Auto/FanControl.jpg

Tips, hints, new views?

Thank you!

 

You could put another relay with a normally closed set of contacts to energize when a/c is turned on, too drop out the low seed circuit.

 

Have a wiring skematic for that Barry or anyone?

 

Try this:

JMC




EDIT: The wire going to pin 86 on the drawn in relay has to go around the ground and not spliced to it as the pic shows. Sorry about that.

 

Thank you sir! Also on the drawn relay there, 87a and 30 got spliced to my ign. on right? And on the draw relay 87 gets left unconnected correct?

Also, does anyone know the color wire for the A/C control i need to tap into and where to find it?

THANKS!!!!

 

On the drawn relay; 30 goes to the ignition hot when on. 87a goes to 86 on the lo speed relay. 86 goes to the A/C clutch. 85 goes to ground and 87 is left alone.


Find the AC clutch and tap into that wire. There is only one wire going to it. The clutch is only engaged when the A/C is on so it will power your relay.



JMC

 

Alright JMC, Thank you so very much! Does this count in the winter too when I turn to other selections since the compressor kicks on in heating too???

 

No only the blower will kick on when its in panel or floor or defrost.

 

Really? Well thats good then. So all other modes the compressor is active?

 

The compressor is active above 45°F give or take a few degrees. It is active in all positions except PANEL - OFF - FLOOR.

JMC

 

Oh so in winter the temp. difference doesn't allow it to run then.

 

Yup.


JMC

 

panel doesnt use the compressor, its the fan blower that you change the speeds with..... floor is the same thing as panel, and depending on where you have the temp, it wont use the compressor

 

OK thanks guys, was confused on that!

 

The limiting factor on weather A/C clutch engages in the A/C positions is the A/C cycling switch not where the temp control is set. If it is 100° out and you set the selector switch to DEFROST the A/C clutch will engage. All the temp **** does is control the blend doors to discharge the selected temperature, Hot or Cold.


The A/C cycling switch monitors the low pressure side of the system. 30psi corresponds to an operating temp of about 32°F. As condensing water drops on the Evaporator core will freeze at this temp the switch is set to open before the freezing occurs. So when the outside temp is about 45° the pressure of the vapor in the evaporator is low enough to cause the switch to open the circuit and disable the A/C compressor.

JMC