relay for electric fan/
- Thread starter browell_66
- Start date
Look for a Bosch 75 amp automotive relay. See Google bosch 75 amp relay - Google Search for some sources.
Don't forget the diode 1N4003 to soak up the EMI pulse generated when the fan and relay turn off. That's about $1
at the local Radio Shack. You' need one for the relay and one for the fan. Or you can buy a relay with the diode inside
and save some effort. However, the fan will still need one.
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.
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.
Don't forget the diode 1N4003 to soak up the EMI pulse generated when the fan and relay turn off. That's about $1
at the local Radio Shack. You' need one for the relay and one for the fan. Or you can buy a relay with the diode inside
and save some effort. However, the fan will still need one.
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.
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.
kpack5982
Yeah, it was pretty stiff, but eventually a buddy
not to hijack, but i tried to search for a temperature switch from the diagram, but not having any luck, has anyone else found one or could give me a part # from a local napa, autozone, or oreillys?
LiquidGT
Member
I'm using a GM style switch and it uses the same 3/8 npt threads that Fords have. The fan comes on like clockwork, I love it.
I bought this one for a 180* thermo. I got part# 601-972 because it comes with the connector. C3 C4 Corvette Cooling Fan Switch 1981-1995 - Mid America Motorworks
If I drive through another winter I'd get a 195* thermo and use this 210-200 switch so I can have stock hot heat again. Low Temp Radiator Fan Switch
These are the cheapest places that you can buy these, I searched all over. The Corvette place seems to have good service, now I get Corvette catalogs in the mail, lol.
I bought this one for a 180* thermo. I got part# 601-972 because it comes with the connector. C3 C4 Corvette Cooling Fan Switch 1981-1995 - Mid America Motorworks
If I drive through another winter I'd get a 195* thermo and use this 210-200 switch so I can have stock hot heat again. Low Temp Radiator Fan Switch
These are the cheapest places that you can buy these, I searched all over. The Corvette place seems to have good service, now I get Corvette catalogs in the mail, lol.
kpack5982
Yeah, it was pretty stiff, but eventually a buddy
thanks for that link. If i don't find one at the parts stores this weekend I'll order that, looks like it'd work perfect.
Anyone know of any that may be carried at a parts store by chance?
Anyone know of any that may be carried at a parts store by chance?
LiquidGT
Member
Nope, I looked through the books behind the counter at the parts stores. There is a VW switch that works nicely, but you'll need a rare tap to make threads with.
The coolest oem GM switch is 220* and some dont even kick the fan on until 240*,
older GMs had to run hot for emissions.The switch has been very reliable so far, I've been running it since last July.
kpack5982
Yeah, it was pretty stiff, but eventually a buddy
well I looked everywhere but no one had the switch in town for the 79 to 82 vw rabbit that I was lookin for. My question is tho, I had that haynes controller for a while, but the wiring in it just isn't up to par for the mark viii. Could I splice in the push in probe and try to use that or is that temperature for one of those controlled by the controller itself, or the probe itself?
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