High Speed Fan Override

[bsan63]

A long time ago there was a link to the High Speed fan override and the use of a monetary switch and a set of relays. The relays were wired in such a way as to allow the monentary switch to be hit to turn on and off the fans. This also allowed the fans to turn off and not come back on once the car was started.

Does anyone have the wiring diagram for the relays?

Thanks.

[RJolly87]

This one?

The problem isn't turning the fan on, or turning it off.

The fan mod is done by grounding the same wire as the pcm to the high speed fan relay on the car. Any switch will do and work fine. Some of us forgetful people see our temps lowered and don't turn the switch off. So far no problem, car is turned off and fans turn off. Upon the next restart the fans turn on and the pcm diagnostic sees the fan on. The service engine soon light comes on to tell you there's a DTC code to help you troubleshoot not turning the switch off to your fan override.

Here's the part, yes a single relay latching itself from momentary switch would work. I'm into options, I want to be able to turn it off and on from a single switch. And a single relay can not do that.

I wanted a latching on/off system and chose to pick up some relays at the junkyard. (Cost: Free) Hook then together properly according to the latching/unlatching setup. I hook the power to ignition power and it automatically resets when the car is turned off.

Diagrams can be found here. 4th or 5th will do a postive output. Add one relay to output ground.
http://www.the12volt.com/relays/page5.asp
Or it could be done via circuitry using an IC flip flop chip
http://www.imagineeringezine.com/PDF-FI ... eshots.PDF
I was unable to appropriate a flip flop yet and therefore haven't finished that part of my project.

[bsan63]

That's it, thank you. Now to get busy making it.

[Mad Myche]

Another circuit that could do this would be to utilize an SCR. An SCR will conduct electricity one the trigger is momentarily charged until their is no current flow. This configuration would only require one other relay. Adding a second relay would allow a configuration that would add in the ability to utilize that same momentary switch to also deactivate the circuit.

Unfortunately I am on my way out the door in a few moments otherwise I would find diagrams for you