2 AUX Fan - How to Turn on both using Rear Heater Swithc (1 Viewer)

[podiev]

Good day,

My rig currently has 2 AUX Fan that are power via individual relays with their own simple rocker switchs.

I happen to have a spare Rear Heater Switch so I used it by providing ignition power to the common Terminal 1 of the switch. Then I connect Terminal 2 to AUX Fan 1 and Terminal 4 to AUX Fan 2. Right now, it's working as follow: LOW powers only Aux Fan 1. Pushing HI powers on AUX Fan 2 only. Only 1 fan can be turned on a time.

However, what I want is as follows:
- Pushing LO powers only Aux Fan 1
- But pushing HI powers both Aux Fan 1 and 2.

Based on the attached diagrams, maybe you can help to configure my wiring. Do I need to add extra relays?

 

[AFinn]

a diode between the fan 1 and fan 2 turn on wires on the back of the relay would solve your dilemma. any radio shack store or like it can hook you up. they are cheap.

 

[podiev]

AFinn -thanks for the fast response. Can you help me further by indicating where specifically should I connect this diode? I searched radioshack and a diode has two ends and further googling shows diodes are unidirectional. Where should I connect End 1 and End 2? Did I get it right in my attached diagram?

Also, how many amps diode should I use? 1amp or 3amps?
3A Barrel Diodes - RadioShack.com

 

[Bjohnston115]

yes a diode will work, making sure you orient it properly so the electricity flows correctly. Use the 3 amp, it wont hurt... Its only a signal so you probably wont see much more than 1 amp.

 

[superjuice]

Put it in between the outputs from the switch. One side of the diode will have a line around it. Place the line side on the high output of the switch. Think of the line as a one way valve that blocks current coming from the opposite end.

 

[podiev]

All - thanks for your input. I got a diode yesterday, tested the configuration, and it worked. The switch now allows me to turn ON either 1 fan only or both fans.

 

[lrowe_csp]

PODLEV:
Was your second diagram correct with regard to the Diode placement, or did you have to flip the diode configuration and place the diode with the line on the diode facing fan 2?

 

[GREATCRUISER]

PODLEV:
Was your second diagram correct with regard to the Diode placement, or did you have to flip the diode configuration and place the diode with the line on the diode facing fan 2?

the diagram is correct. current flows from the anode to cathode so the side the band is closest to is the cathode.

 

[alaskacruiser]

Podiev- please post some details and pics if possible of how you have these mounted.

 

[wesayso]

Silly question - what are the fans for?

 

[40hazjo]

silly question - what are the fans for?

rear heater

 

[podiev]

These fans are auxilliary fans mounted in front of the condenser: to improve AC performance when idling - search the forum - there's a lot of discussions already on this.

Unfortunately, I don't have pics and I used only surplus Japanese fans from junk yards (I'm from the philippines) so sourcing OEM parts are quite expensive.

Anyway, attach is my post-setup wiring diagram. After learning about this diode, I figured I cannot pass on 12V to the Switch as it conflicts with the Lights On wiring. Which I need so I would know the fans are on. So I had to use Ground as input to the Switch and pass that on to the individual Relays (R1 and R2) of the Fan. When I did the original wiring of these 2 aux fans about 2 years ago, I mounted the relays on a custom fuse box in the engine bay and run wires to the firewall for the improvised dash switches. Since I don't want to fiddle anymore with the current setup, I just added 2 more relays (R3 and R4)behind the dashboard to control the passing of trigger signals to the main relays. The additional relays receive Ground signal from the Rear Heater Switch. The Setup works - no problems encountered.

Thanks for the forum for enlightening me on the use of diodes. Now I have another "control" mechanism to use for future self-wiring exercises.

i'll try to get pics this weekend of how the 2 fans were mounted.


H