Radiator Cooling Fan Switch Question

[SCFFR]

To control the radiator cooling fan, I'm using a thermostat sensor installed in the intake manifold. According to the Ron Francis wiring manual, you can either use a simple ON-OFF switch to manually control the fan or use a sensor. If you decide on the sensor, the instructions state to connect the switch wires together (to close the circuit).

I've read a couple of posts where the owner decided to use both with the thinking that it would be good to have the ability to override the thermostat sensor. Sounds like a good idea so was considering the same but wouldn't the switch have to stay on all the time to close the circuit so the thermostat sensor could work when the temps reached the operating range of the sensor? Also, if you forgot to cut the switch on, the thermostat sensor couldn't work at all. If the sensor went bad, would the manual switch still work?

Thanks for your feedback.

Ron

[Jeff Kleiner]

Wire it with the manual dash switch using the brown "fan switch feed" wire for power in and the orange "cooling fan" wire that carries a switch signal to the relay. You'll find both of these wires are in the dash harness. If you want an indicator light (I like to use an amber one to show when it is on) tap one side of the lamp into the orange and take the other side to ground. Now, for automatic operation pick up a Painless thermostat switch. It is a true, normally open thermostatic switch with two female spade connections, not a grounding switch like the FFR supplied one. Wire it in parallel with the manual dashboard toggle; i.e. one side to the brown feed wire the other to the orange load wire. Screw it into a coolant port in the intake or thermostat housing and you're done; no reconfiguring of the relay as would be necessary with the FFR grounding switch and the entire circuit is still protected by the 30 amp "cooling fan" fuse. Simple as that--- you will now have automatic operation even when the dash switch is off as well as manual fan control via the dash switch and an indicator light to let you know anytime the fan is running! Painless switch #30111 turns on at 185* and off at 170* (perfect for a 180* stat) but there are others available with different on/off setpoints.

Painless Wiring 30111 - Painless Performance Temperature Sending Units - Overview - SummitRacing.com (http://www.summitracing.com/parts/PRF-30111/)

Hope that helps and good luck!

Jeff

[CraigS]

I preferr to use both the temp sensor and the dash switch to ground the relay coil. I especially like this for the long run to the dash switch. If there were ever any damage to that wire all that would happen is that the fan would turn on.

[SCFFR]

Jeff - thanks for the information. Just to be sure I understand correctly, I have the Painless thermostat sensor (#30111) in the intake manifold and connected to the green thermo switch wire on the Ron Francis harness (plus a ground). Is this correct or is the wiring configured for a different type sensor supplied by FFR? Are you saying that the wires to the Painless sensor should be the brown and orange ones?

Ron

[mike w]

To control the radiator cooling fan, I'm using a thermostat sensor installed in the intake manifold. According to the Ron Francis wiring manual, you can either use a simple ON-OFF switch to manually control the fan or use a sensor. If you decide on the sensor, the instructions state to connect the switch wires together (to close the circuit).

I've read a couple of posts where the owner decided to use both with the thinking that it would be good to have the ability to override the thermostat sensor. Sounds like a good idea so was considering the same but wouldn't the switch have to stay on all the time to close the circuit so the thermostat sensor could work when the temps reached the operating range of the sensor? Also, if you forgot to cut the switch on, the thermostat sensor couldn't work at all. If the sensor went bad, would the manual switch still work?

Thanks for your feedback.

Ron

The dash switch works to ground the thermostat sensor switch before the temperature rises to do it automatically. So when your dash switch is off, there is no ground to the thermostat switch (except when it closes automatically). When you turn your switch on, you are grounding the thermostat switch causing the fan to turn on.

[Jeff Kleiner]

Jeff - thanks for the information. Just to be sure I understand correctly, I have the Painless thermostat sensor (#30111) in the intake manifold and connected to the green thermo switch wire on the Ron Francis harness (plus a ground). Is this correct or is the wiring configured for a different type sensor supplied by FFR? Are you saying that the wires to the Painless sensor should be the brown and orange ones?

Ron

If you do indeed have a Painless switch (2 terminals, not one as on the FFR grounding switch) do just as I said above, running it in parallel with the dash switch which is getting power through the brown wire and sending an activation signal to the relay through the orange. So... tap an additional wire into the orange wire at the toggle switch and run it out to one side of the Painless switch. Tap an additional wire into the brown wire at the toggle and run it out to the other side of the Painless switch. That's it unless you want an indicator in which case you tap yet another wire into the orange and run it to one side of the lamp and ground the other side of the lamp. The green wire only comes into play when using a grounding switch and requires reconfiguring wires at the relay---I do not know why RF didn't set it up in that configuration to begin with.

Jeff

[SCFFR]

Thanks again for the information. I went out into the garage and tested the setup I currently have. I connected the cooling fan to the RF harness, put a jumper wire between the brown and orange wires (where the manual switch would go) and then put a jumper wire across the two terminals on top of the Painless thermostat sensor and the fan started running so I know what I have will work. As the saying goes, "if something is working, don't try to fix it" so I think I will just leave it as is and just connect the orange and brown wires together and depend on just the sensor to operate the fan. I have all of the harness nicely wrapped/routed through grommets in the firewall so I really don't want to cut into them to run more wires to the thermostat sensor.

Again, many thanks for the feedback and information.

Ron

[SCFFR]

Jeff - I think I have come up with a way to tie in a manual switch without having to cut into my engine harness and run additional wires out to the thermostat sensor. When I tested my system before, the fan came on when I jumped the terminals on the sensor. I am thinking that if I splice into the green sensor wire before it goes into the fuse panel and then run a wire up to one connector on a simple SPST ON-OFF switch. I could then run a ground wire from the second switch connector. When the switch was on, the sensor circut is grounded and the fan will come on. With the switch off, the fan will still come on when the sensor reaches its operating range. What do you think?
Thanks again,
Ron

[Jeff Kleiner]

Neither terminal on the Painless sensor goes to ground; it only opens and closes +12v. power to the relay just like an on/off switch. If you ground one of the terminals it will create a dead short (depending on which side was grounded it would either be immediately when the ignition was turned on or when the switch closes at activation temperature).

I'm afraid you've kind of lost me; what wires do you have running to the temperature switch on the engine? What are you feeding +12v. to the temp switch with and where does the output connect? If you connect the orange and brown wires together the fan will run any time the ignition is on...period...even if the Painless switch is not installed. Long story short you should be feeding into both the temperature switch and the manual toggle with the brown and outputting from both to the orange. If you do this either will control the fan (via the relay) independent of the other.

Jeff

[SCFFR]

Jeff,
Again thanks for your feedback and sorry for the confusion I'm causing. I tested the cooling fan setup again by putting a jumper wire between the brown (gauge feed) and orange (fan switch) wires. I turned the ignition switch on and then put a jumper wire across the two terminals on top of the Painless thermostat sensor and the cooling fan started (Note that with the orange and brown wires connected and the ignition on, the fan does not come on unless I jump the two terminals on the top of the Painless thermostat sensor). I took my voltmeter and measured 12.5 volts at the terminal with the green wire (the fan thermo wire on the Ron Francis harness). I assumed this was correct.....when the sensor reached operating temp, the contact would close (like I did with the jumper wire) and the fan comes on. However, I know how assumptions can come back to bite you!

You mentioned that the sensor should not be grounded but the Painless instructions that came with the fan relay kit (I mistakenly bought the entire kit instead of just the sensor) does show a ground wire on one of the sensor terminals. I used this same setup on another car several years ago and have had no issues with the cooling fan. This is how I wired my sensor - the green (fan therm switch) wire on one terminal and I added a black ground to the other terminal. I have no experience with the FFR sensor (one wire) but wondering if the threaded part provides the ground so maybe the two sensors work the same way.....the Painless sensor just has a separate ground wire. However I understand that the Painless and FFR system are probably completely different so my assumptions are likely out of line.

I'm sure that I'm making this way more complicated than it should be. My solution was to basically add a second sensor wire and connect it to a ON-OFF switch. Turn the switch ON and it grounds the circuit and the fan comes on. Although this looks like it will work, it doesn't appear to be the correct way to do it.
Thanks again for everyone's input. I can see that I am causing more confusion than solutions. Until I get the engine running and up to temperature and see exactly how the sensor reacts, I can't be sure that the setup I have will operate correctly.

Ron

[Avalanche325]

I did mine like CraigS. If you think more about how to activate the relay, than how to power the fan, it simplifies the thought process.