Grounding Fan Relays with a 2 Position Switch
09-04-22, 03:25 PM
#1
Grounding Fan Relays with a 2 Position Switch
So...I toggle the AC on low, to kick the fans on when I'm cruising. But, I'd rather just flip a switch to kick in some extra cooling. If I patch a few/couple of the fan relays to ground via a switch, will it work? I also have the cooling recall harness and am digging around for the test "switch" behind the ecu.
I believe patching the relays is how the old-school fan controllers work, in part. RE-A used to list a sub harness for this purpose, but I don't see it on RHD japan.
Just thought I'd see what y'all think of it. Has anyone done similar.
calling @DaleClark the fan master
I believe patching the relays is how the old-school fan controllers work, in part. RE-A used to list a sub harness for this purpose, but I don't see it on RHD japan.
Just thought I'd see what y'all think of it. Has anyone done similar.
calling @DaleClark the fan master
09-04-22, 03:47 PM
#2
RX-7 Bad Ass
iTrader: (55)
Yeah that would be easy to do. Each fan relay should have a ground input to kick the relay on, you just have to short that pin to ground and ta da, fans are running on 1 speed.
Dale
Dale
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Narfle (09-04-22)
09-04-22, 03:53 PM
#3
I’ve just been through the whole fan troubleshooting so it is pretty fresh.
If you put a switch on the ground signal on relay #1 (the one that looks different) that controls the AC fan that should work. It is the violet wire. The black/yellow always has ignition 12v so if you ground the violet wire it will turn the fan on and you will have manual fan control.
There is probably a few ways to do this so I’m curious to see what others suggest.
If you put a switch on the ground signal on relay #1 (the one that looks different) that controls the AC fan that should work. It is the violet wire. The black/yellow always has ignition 12v so if you ground the violet wire it will turn the fan on and you will have manual fan control.
There is probably a few ways to do this so I’m curious to see what others suggest.
09-04-22, 11:24 PM
#4
I agree hijacking the Relay #1 trigger would be a good way to do it, without preventing the ECU fan control from working. A clean way to do it would be using a single pole dual throw switch (SPDT), connect the center pin of the switch to the relay side of the trigger wire (service manual shows this as violet with a pink stripe), connect the normally-closed pin of the switch back to the original violet/pink trigger signal from the HVAC controls, and connect normally-open pin to chassis ground (run a new wire). When the switch is in the 'off' position, the system will work like normal. When the switch is in the 'on' position, the normally-open pin will connect to the center pin and the relay side of the violet/pink wire should connect to ground and trigger both fans to run at low speed. If the ECU is also trying to trigger the fans, they should run at medium high speed. And if the thermoswitch and ECU trigger and your switch are all active, the fans will run at high speed.
The hard part will be grabbing the violet/pink wire at the right location, according to page Z-70 of the 1994 wiring diagram it branches off to a few different places in the harness. It should be safe to grab it in the Front harness, but not in the Dash harness. That might be tricky, since there's not a lot of space to work with those wires under the dash.
The hard part will be grabbing the violet/pink wire at the right location, according to page Z-70 of the 1994 wiring diagram it branches off to a few different places in the harness. It should be safe to grab it in the Front harness, but not in the Dash harness. That might be tricky, since there's not a lot of space to work with those wires under the dash.
09-04-22, 11:44 PM
#5
I agree hijacking the Relay #1 trigger would be a good way to do it, without preventing the ECU fan control from working. A clean way to do it would be using a single pole dual throw switch (SPDT), connect the center pin of the switch to the relay side of the trigger wire (service manual shows this as violet with a pink stripe), connect the normally-closed pin of the switch back to the original violet/pink trigger signal from the HVAC controls, and connect normally-open pin to chassis ground (run a new wire). When the switch is in the 'off' position, the system will work like normal. When the switch is in the 'on' position, the normally-open pin will connect to the center pin and the relay side of the violet/pink wire should connect to ground and trigger both fans to run at low speed. If the ECU is also trying to trigger the fans, they should run at medium high speed. And if the thermoswitch and ECU trigger and your switch are all active, the fans will run at high speed.
The hard part will be grabbing the violet/pink wire at the right location, according to page Z-70 of the 1994 wiring diagram it branches off to a few different places in the harness. It should be safe to grab it in the Front harness, but not in the Dash harness. That might be tricky, since there's not a lot of space to work with those wires under the dash.
The hard part will be grabbing the violet/pink wire at the right location, according to page Z-70 of the 1994 wiring diagram it branches off to a few different places in the harness. It should be safe to grab it in the Front harness, but not in the Dash harness. That might be tricky, since there's not a lot of space to work with those wires under the dash.
09-05-22, 02:06 AM
#6
Don't just tap onto the violet/pink wire, that appears to connect to the AC request switch on the dash so grounding it might make the ECU think you want the AC to run.
Intercepting the violet/pink wire near the relay would work also. There's more room to work in the engine bay, but you'll need to worry about weatherproofing your splices. I like uninsulated crimps (you can probably find them in the electrical section at Ace Hardware) and SCL heat shrink (I don't know of any type of stores that stock it, unfortunately). The heat shrink isn't too expensive but can be tricky to guess the right size. I took some measurements on my car, the trigger wires are about 1.6mm OD (including the insulation), my guess is about 20-22 AWG stranded wire.
Adding a second 22 AWG wire should fit in a 14-16 AWG splice, or maybe a 18-22 AWG splice. These ones are nice if you can wait for shipping time:
https://www.prowireusa.com/19205-0001 , this is the larger one that should fit but may be slightly big/loose. I would buy at least two spares so you can do practice crimps.
https://www.prowireusa.com/19207-0001 , this is the smaller one, might be too small to fit two 20AWG wires side-by-side. I would buy at least two spares so you can do practice crimps.
This 3/16" SCL heat shink should be the right size to fit around the crimp and also shrink small enough to have a chance at sealing around the wire:
https://www.prowireusa.com/p-187-3-1...ed-tubing.html
Prowire also sells nice 22 AWG wire, this is black 22AWG TXL wire. It's better quality than the original Mazda wire, reasonably priced and without the fancy Tefzel insulation found on the fancy lightweight aircraft-spec wire. Tefzel insulation is nice but so thin and strong it can be hard to work with. They also sell 20 AWG wire, but less chance that will fit in the smaller splice.
https://www.prowireusa.com/p-3091-txl-22-ga-black.html
A 1/4" ring terminal (18-22 AWG wire size) should fit well with any M6x1.0 bolt (those are the common ones in the engine bay, 10mm wrench). There are some nice ring terminals on the ProWireUSA website, but it's a pack of 100 so I might pick up just a few from the local hardware store instead.
It's possible to spend a lot of money on crimp tools, and a good idea if you're doing lots of wiring work. But you can also get decent results from inexpensive ones, especially if you buy enough spare wire and crimps to do a few practice splices beforehand. Budget crimper tools like these should work:
https://www.lowes.com/pd/Kobalt-KBLT...-In/5001674133
https://www.lowes.com/pd/IDEAL-Crimper/1083479
Personally I wouldn't bother intercepting multiple relays. Running the fans at low speed should be good enough to cool the car down when it's idling or driving slowly. If not, check that both fans are actually spinning. It's common for unsealed batteries to leak acid on the driver side fan, this can completely kill the fan motor it if you're unlucky.
Intercepting the violet/pink wire near the relay would work also. There's more room to work in the engine bay, but you'll need to worry about weatherproofing your splices. I like uninsulated crimps (you can probably find them in the electrical section at Ace Hardware) and SCL heat shrink (I don't know of any type of stores that stock it, unfortunately). The heat shrink isn't too expensive but can be tricky to guess the right size. I took some measurements on my car, the trigger wires are about 1.6mm OD (including the insulation), my guess is about 20-22 AWG stranded wire.
Adding a second 22 AWG wire should fit in a 14-16 AWG splice, or maybe a 18-22 AWG splice. These ones are nice if you can wait for shipping time:
https://www.prowireusa.com/19205-0001 , this is the larger one that should fit but may be slightly big/loose. I would buy at least two spares so you can do practice crimps.
https://www.prowireusa.com/19207-0001 , this is the smaller one, might be too small to fit two 20AWG wires side-by-side. I would buy at least two spares so you can do practice crimps.
This 3/16" SCL heat shink should be the right size to fit around the crimp and also shrink small enough to have a chance at sealing around the wire:
https://www.prowireusa.com/p-187-3-1...ed-tubing.html
Prowire also sells nice 22 AWG wire, this is black 22AWG TXL wire. It's better quality than the original Mazda wire, reasonably priced and without the fancy Tefzel insulation found on the fancy lightweight aircraft-spec wire. Tefzel insulation is nice but so thin and strong it can be hard to work with. They also sell 20 AWG wire, but less chance that will fit in the smaller splice.
https://www.prowireusa.com/p-3091-txl-22-ga-black.html
A 1/4" ring terminal (18-22 AWG wire size) should fit well with any M6x1.0 bolt (those are the common ones in the engine bay, 10mm wrench). There are some nice ring terminals on the ProWireUSA website, but it's a pack of 100 so I might pick up just a few from the local hardware store instead.
It's possible to spend a lot of money on crimp tools, and a good idea if you're doing lots of wiring work. But you can also get decent results from inexpensive ones, especially if you buy enough spare wire and crimps to do a few practice splices beforehand. Budget crimper tools like these should work:
https://www.lowes.com/pd/Kobalt-KBLT...-In/5001674133
https://www.lowes.com/pd/IDEAL-Crimper/1083479
Personally I wouldn't bother intercepting multiple relays. Running the fans at low speed should be good enough to cool the car down when it's idling or driving slowly. If not, check that both fans are actually spinning. It's common for unsealed batteries to leak acid on the driver side fan, this can completely kill the fan motor it if you're unlucky.
09-05-22, 03:27 PM
#7
There is a old school mod for this. I had done it at one time too, untill I replaced my stock ECU. Think it's called foglight switch to fan mod, just Google it for the directions. If you don't have fog lights you can use the factory fog light switch and mod it to work and fits in the center console etc. It was pretty handy as I recall.
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