EITHER thermo fan switch OR manual fan switch

[Bren]

So, the RF wiring manual says that it's wired for running the cooling fan for "both" a thermostatic switch and a manual switch. What they mean to say is that it's wired for either one, but not both.

I just finished wiring the dash and was testing everything when I found this out. I have a dash switch mounted and wired to the orange fan wire that supplies power to the under dash relay AND a thermo switch on the motor that grounds the relay (blue). So, to turn the fan on, the switch must be on, and the thermo switch on/grounded/at temperature. Obviously, I want either the dash switch or the thermo switch to run the fan.

What's the best way to accomplish this? Is there a way to re-do the wires in the fuse panel that go to the relay? I thought I'd ask here first before ripping out wires in the fuse panel and damaging the plastic so that nothing will fit right again.

[Jeff Kleiner]

Look back st some of your earlier posts. I'm pretty sure that I posted my instructions for using a Painless thermo switch in parallel with the dash toggle in response to a similar question you asked recently (don't recall if it was here or on FFCars). It doesn't require any reconfiguring of wiring at the relay at the fuse panel

Jeff

[Feen]

Do it the way Jeff posted, you do not need to re-work the fuse panel or relays. If I remember right, you will need to ground the green "thermo switch feed" in the RF harness

[jakester888]

This sounds like a familiar problem! Wow, thanks.

[Bren]

I ended up fixing the problem by turning the switch on the dash into a ground switch instead of a power switch. Basically, I spliced the green wire that goes from the relay to the thermostatic switch and ran the spliced wire to the dash switch that went to ground. It's working so far.

I like this solution better than Jeff's (no offense, just personal preference) because I wanted to use the thermo switch I already bought and I didn't want to run another wire to the engine. Whether it's a ground switch or a power switch, electrically it does not matter.

[jakester888]

Jeff or Bren, I am not comprehending your solution. Can you sketch it out?

[Bren]

Jeff or Bren, I am not comprehending your solution. Can you sketch it out?

32801

[jakester888]

32801

Bren : thanks for the drawing but I still don't get it. Please excuse me in advance for being a dipstick.

According to the Ron Francis manual, there are 2 wires that connect to the fan switch in the dash. The Brown "Fan Switch Feed" on Lead 1 and the Orange "Cooling Fan" which comes from the relay on Lead 2. I think you're saying forget about Orange & Brown. Instead I think you're suggesting to connect the Green "Thermo Switch" wire (which is in the engine bay and normally destined for thermo switch on the lower intake) to Lead 1 and the Black "Ground" wire to Lead 2 of the fan switch in the dash.

Or are you saying connect both Orange & Green to Lead 1 & Ground to Lead 2 and forget about brown? See below for pics:

Ron Francis Method:
32842

Bren Method 1 (my interpretation):
32841

Bren Method 2 (my interpretation):
32843

Am I close?

[Avalanche325]

To make it simple, all you are doing is completing the ground circuit on the control side of the fan relay.
The thermo switch does it. The dash switch does it.
Parallel circuits.

[Bren]

Use "Bren Method 1." The wire you labeled "Green Thermo Switch" should be spliced with the wire that goes to the thermo switch in the engine. This can be done in the fuse panel. Also, the orange and brown RF wires behind the dash need to be connected. If I remember right, the brown wire connector has two wires in it, and the orange has only one. I cut off the connector on the end of the orange wire with only one wire in the connector and put a male blade connector on it instead. Then, I plugged the orange wire into the brown wire.

[jakester888]

Use "Bren Method 1." The wire you labeled "Green Thermo Switch" should be spliced with the wire that goes to the thermo switch in the engine. This can be done in the fuse panel. Also, the orange and brown RF wires behind the dash need to be connected. If I remember right, the brown wire connector has two wires in it, and the orange has only one. I cut off the connector on the end of the orange wire with only one wire in the connector and put a male blade connector on it instead. Then, I plugged the orange wire into the brown wire.

Makes sense. I'll try it out and report back. Thanks again.

[Avalanche325]

Just remember that what the switch (either the thermo or dash) does is complete the ground on the control side of the relay.

They are a parallel circuit.

[CraigS]

Bren that is the way I always wire it. One theory says that this way you keep all the power wires in the engine compartment and therefore as short as possible. Less volt drop and less chance of damage. The longest wire is to the dash switch. The advantage here is that, if that wire were to be damaged and grounded, all that would happen is the fan would come on. Current cars are running so many ecu circuits that it's not as obvious as it used to be. But every circuit that was possible was wired this way and still is. A large percentage of switches of all types control the ground of the circuit.

[jakester888]

Makes sense. I'll try it out and report back. Thanks again.

Bren : it works, thank you.

[Bren]

Bren : it works, thank you.

Glad I could help.