Once again I have a question that likely has a simple solution that I can’t figure out on my own. My trusty daily driver El Camino has a great air conditioner. It will blow a lot of 40 degree air on a 100 degree day. That is as long as you are moving. Once I come to a stop at one of the many LONG red lights the cold air becomes not so cold. I added a 12 inch Spal pusher fan right in front of the condenser which sits right in front of the radiator. The water temp is not the issue it is the lack of air to the condenser. The fan makes a huge difference and the air stays cold now. All of this is because I like to tinker and make things better than GM did in the 80s. Sometimes that is not hard at all.
The point of the post is the fan is not needed at all if I am moving more than 25 MPH. The fan only runs when the compressor runs so it cycles on and off a lot under light AC loads. It starts to whistle at speeds above 40 MPH. It is not doing anything at that speed and is unnecessary. If the fan is not running it does not whistle at speed.
My goal is to figure out a way to make the fan run only when stopped or the car is moving below 10 MPH. It is not a temperature thing. The water temp is fine with the big radiator I have. The AC system is typical GM orifice tube system. I can’t see using a pressure sensor to run the fan. Right now it reads the 12 volt signal from the compressor clutch to pull a relay to start the fan. It cycles perfectly with the compressor.
There is a speed sensor on the speedometer that the fuel injection system reads but I have no idea how to tap into that signal. Throwing away that carburetor and going to fuel injection is the best thing I ever did to the Elky.
I could put in a manual toggle switch that activates the system only when needed but that is just not an elegant solution. Every time I come to a light flipping a switch instead of watching traffic just does not make sense. I can just ignore the fan noise and it does not hurt anything for it to run.
Any suggestions?