Electric fan question

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The switch method is not a very good idea. To many things to go wrong with forgettting to turn on/off. If you definately are going that route, you will need:
1. 3G upgrade.
2. 10 AWG wire.
3. 30-40A relay.
4. 30A fuse.
5. Switch.

I would not do it that way. I would add some type of controller:
6. Fan controller / if you are good with electronics you can make an adjustable one for ~$30 (which I would say you are not or you wouldn't be asking this question so you should look for one through summit or somewhere ~$80)).

Do a search and you should find everything you need.
 
If you don't have a high current alternator, you can forget about using an electric fan. The stock 65 amp alternator on 86-93 Model Mustangs isn't big enough to run the fan and the rest of the car.

Switching a fan on and off manually is a bad idea. Too many guys have been distracted (hot girl kissing on their neck, too much to drink, dog tired and not thinking clearly) and cooked things because they forgot to flip the switch. An equal number have forgotten to turn the switch off for the same reasons and run down their battery.

The best fan controller available today is a DC Control unit. Now serving. Cost is about $110. Be prepared to wait 4 weeks or more to receive your controller once you have sent in your payment. The controllers are custom made in small lots and lead times can stretch out.

Next best is a SPAL controller - $70-$90 See http://www.spalusa.com/fans/automated/accessories/fanpwm.html. Ebay will have the controllers for the $70: do a google search and see what you find.

At the bottom are the Hayden or Imperial controllers available through Advance Discount Auto Parts and AutoZone. The non adjustable one is about $30 ( Hayden 226206) and the adjustable one is about $60 (Hayden 226204). I recommend you do a Google search on Hayden and the part number for more info.

Do not use a simple on/off switch without using a relay. The current load can burn up the typical cheap automotive switch very quickly. The fan draws 30+amps and you need to use #10 wire on the fan power and ground wiring.

If you are good with electrical stuff (90% of the people here aren't), build your own controller. The numbers on the diagram (#86, #87, etc) refer to the numbers on the bottom of a typical automotive relay.

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Note that the thermostat switch in the diagram isn’t really suited for the job. You’ll have to do a Google search and find your own.

This version of the fan controller will continue to run the fan after the ignition switch is turned off, just like most new cars.
To allow the ignition switch to control the fan so that it does not run when the ignition is off, connect the relay contact #86 to the red/green wire on the ignition coil or to the red/yellow wire on the coolant level sensor.

If you are an experienced electronics tech or electrical engineer, email me and I will send you the prototype drawings of a fan controller that is probably as good as the DC Control unit. It is a build it, troubleshoot it yourself item. I will not build or troubleshoot units, so it is not suitable for anyone who isn't really good with electronics.

Alternate placement for a temp gauge sender or temp switch/temp sensor for an electric fan. Use the heater feed that comes off the intake manifold. Cut the rubber hose that connects the manifold water feed to the heater and splice in a tee adapter for the temp gauge sender. Be sure to use the same water feed line as the ECT sensor. That way you will get the most accurate temp readings.

Tee adapter info:
Make a pilgrimage to your local hardware or home supply center and get some copper pipe and a tee that fits the temp gauge sender. Solder two pieces of copper pipe onto a copper pipe tee with threads in the tee part. Find the correct brass fitting to match the temp sender threads to the tee fitting.

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Hey jrichker, couldn't you use tap the t-stat housing for that temp fitting? There's a dimple on it for just that reason...been meaning to do that for a loooong time now.


Something i thought about doing for the on-off switch method is wiring up a door dinger style buzzer so that if you turn the car off it starts dinging like it would if you left your keys in...just to try to keep from forgetting. Mine is hooked up with a temp switch right now but a write up using a dinger might help someone else.
 
Hey jrichker, couldn't you use tap the t-stat housing for that temp fitting? There's a dimple on it for just that reason...been meaning to do that for a loooong time now.

I Remeber correctly, the boss cast into the thermostat housing is placed after the thermostat. That means the gauge only accurately reads the coolant temp after the thermostat opens.

Use the red/green wire for the ignition coil to power the fan relay. Put the temp switch in ground side of the relay circuit. That way, when you turn off the ignition swich, the fan shuts off.

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