I just did some more testing with my multimeter to try figuring out what each of the four driver side factory wires are that connected to the factory fan, and here is what I've found:

• Solid Blue Wire
  • When probing this wire Key Off, reb probe to wire and black probe to negative, I get 0V. Other way around, I also get 0V
  • When probing this wire Key ON, I get 0V both ways
  • When probing this wire with the Engine Running, I get 0V both ways unless I turn on the HVAC fan. When the interior HVAC fan is on, I get 12V signal (red to wire, black to negative)
• Blue/White
  • When probing this wire Key Off, reb probe to wire and black probe to negative, I get 0V. Other way around, I also get 0V
  • When probing this wire Key ON, I get 0V both ways
  • When probing this wire with the Engine Running, I get 0V both ways
• Black/White
  • When probing this wire Key Off, red probe to wire and black probe to negative, I get 0V. Other way around, I get 12V, indicating this is in fact a ground which explains why my fans turned on when I previously connected Pin 85 to this wire with the Key On.
  • When probing this wire Key ON, I get 0V from red to wire and black to negative, but 12V when black to wire and red to positive terminal, once again confirming this is a ground.
  • When probing this wire with the Engine Running, I get 12V as a ground only.
• Solid Black
  • When probing this wire Key Off, red probe to wire and black probe to negative, I get 0V. Other way around, I get 12V, indicating this is another ground.
  • When probing this wire Key ON, I get 0V from red to wire and black to negative, but 12V when black to wire and red to positive terminal, once again confirming this is a ground.
  • When probing this wire with the Engine Running, I get 12V as a ground only.

I'm a bit confused why the Solid Blue wire only sees 12V when the interior HVAC fan is on. Does the factory radiator fan only run when the HVAC fan is selected on? I can't recall.

Your understanding of how the 2g controls the fans is not even close - it's way more complicated. The factory fans are 3 speeds each. The ECU uses voltage combinations on those 4 wires (through 4 relays) of each of those factory fans to control their speeds based on engine temp, vehicle speed, and AC on/off (https://www.dsmtuners.com/attachments/fan-operating-mode-2g-jpg.86862/).

Since you only have single speed fans, you should just use the factory fan harness wires (which already use the original factory relays) wired up as follows: https://www.dsmtuners.com/threads/fans-running-all-the-time.261629/#post-151198132.

luv2rallye said:

Your understanding of how the 2g controls the fans is not even close - it's way more complicated. The factory fans are 3 speeds each. The ECU uses voltage combinations on those 4 wires (through 4 relays) of each of those factory fans to control their speeds based on engine temp, vehicle speed, and AC on/off (https://www.dsmtuners.com/attachments/fan-operating-mode-2g-jpg.86862/).

Since you only have single speed fans, you should just use the factory fan harness wires (which already use the original factory relays) wired up as follows: https://www.dsmtuners.com/threads/fans-running-all-the-time.261629/#post-151198132.

Click to expand...

Thanks for the link. Very helpful.

I ended up getting them to work today. Perhaps not the best setup, but know I can at least command them on.

Here's what I did.

I tied the two power wires from the driver side harness as my 12V switched power for the standalone relay I had already partially installed. I then grounded my relay, and have power to the fans when I turn on the interior HVAC. Hoping the ECU temp also triggers them on, but regardless, I'll always be driving the car with the interior air on any ways since it's a summer car. So, I know they'll be on when driving.

1) From your post #4 description it's unclear which relay pins you connected to what since you never stated this. Using the correct relay pins is important. Examples: "grounded my relay" - which pin? And "I tied the two power wires from the driver side harness as my 12V switched power for the standalone relay" - which relay pin(s) and which color wires? Please specify what each relay pin is connected to. Connecting them wrong might make it work now but can be a safety issue or cause future problems.

2) (a) I wish you'd wire the fans as in my link which is the correct way (I've been working on cars for 50 years and am an electrical engineer so know what I'm talking about with electrical). For safety EACH fan should ALWAYS have its own relay which this does (the car's factory relays which are already being used - {even your way uses them but your added relay forces ALL of both fans current to go through only ONE relay which can be dangerous or over driving the relay [even though I know, the relay says its rated at 30 amps - but there are turn on and off spikes that can deteriorate/destroy a 30 amp relays contacts with time]}). (b) Also your way will only turn the fans on for the ROWS listed in the "Fan Operating Mode" chart (https://www.dsmtuners.com/attachments/fan-operating-mode-2g-jpg.86862/) which have a "20" under the column I added called "ECU pin low". They will not turn on for other ROW cases. (c) Your way adds a relay and new wires. My way doesn't add anything, just twist some existing wires together (with connectors or solder them).

If what I've done can cause damage, I'll definitely correct it.

These pics are probably going to come out quite blurry, but one is a wiring diagram I got for a 1998 Eagle Talon 2.0L TSI.

This diagram shows 4 relays on the right side of the drawing label top to bottom as follows: Condenser Fan Relay (LO), Condenser Fan Relay (HI), Radiator Fan Relay (LO1), Radiator Fan Relay (HI). On the bottom left of the diagram is the Radiator Fan Relay (LO2) and on the top left shows Automatic Compressor ECM which uses the AC dual pressure switch.

Since, I connected to wire from the drivers side 4-pin factory connector, the two relays being used are Radiator Fan Relay (LO1) and Radiator Fan Relay (HI). Each relay in the diagram is label as 1 (GRN/ORG) which is the ECU Ground, 3 (BLU/RED) which is the 12V switched power, 4 which is labelled as WHT/BLK for Radiator Fan Relay (LO1) and WHT/BLU for Radiator Fan Relay (HI), and 5 (RED/BLU) which is the 12V battery power supply through the 30A fuse in the fuse box. If I was to think of these as standard relay numbers, 1 would be 85, 3 would be 86, 4 would be 87, and 5 would be 30.

At the bottom of the diagram, it shows the Radiator Fan Motor with 4 wires. 1 (WHT/BLK) coming from Pin 4 on the Radiator Fan Relay (LO1), 2 (BLK) going to chassis ground, 3 (WHT/BLU) going to Pin 4 on the Radiator Fan Relay (HI), and 4 (BLU/GRN) which is the ground connection from the Radiator Fan Relay (LO2) located on the far left of the drawing.

My car has Solid Blue, Solid Black, Blue/White, and Black/White wires. When I did a continuity test with the Ignition OFF, the Black and Black/White wires both indicated they are grounds. Indicating the on my car Pins 1 and 4 on my Radiator Fan Motor connector are reversed for what the diagram shows, so the Solid Blue actually connects to the Radiator Fan Relay (LO1) Pin 4 instead of the ground.

So ultimately what I've done, possibly in the short term, is connect the Solid Blue and Blue/White wires from my factory 4-pin harness to Pin 86 on my stand alone relay to be used as the 12V switched power signal for the relay. Pin 85 connects to the Solid Black chassis ground wire, Pin 87 connects to the positive leads on my fans, and Pin 30 connects to battery supplied power. I then chassis grounded the fans.

I'm by no means and electrical engineer, and certainly appreciate your expertise. Wiring is not my specialty. I'm a Petroleum Engineer and 1st Class Power Engineer, so I can somewhat figured out wiring diagrams, but it's confusing when wiring colors don't match the schematics and test results don't go as planned.





Note, my stand alone relay is a 50A and I also added an inline 30A fuse for the hot wire connecting to Pin 30.

I looked over your wiring ("So ultimately what I've done...") which BTW is a perfect write-up of what you did (as I requested from you, thanx), and I can say you've got it correct for just using one relay! Good job. Use a minimum wire size of 14 gauge (AWG) going to each fan from the relay pin 87 (separate wire for each fan), and 12 gauge minimum from battery positive to the relay pin 30.

One thing that you (and many others) get wrong is that the drivers side fan is the Condenser fan. Passenger side is the Radiator fan. So the drivers side fan uses relays Condenser Fan Relay Hi and Condenser Fan Relay Lo. This is why I asked you for the wire colors you used. Since you used the correct wires it didn't make any difference - just a fan name change.

Another tid bit. Wire colors can fade with age so it can get misleading. When you said "My car has Solid Blue, Solid Black, Blue/White, and Black/White wires", the Black/White is actually Black/Blue but the Blue has faded into White misleading you (or maybe you didn't wipe it off and look closer all around it).

I have the real Mitsubishi Eclipse factory manual 3 volume set which I use nearly every day to help dsm'ers with issues (especially electrical which is my specialty). I'm retired and do this as a volunteer. Electrical is difficult for many so I enjoy helping. I also help with many non-electrical issues.

Thanks, Gary.

That misunderstanding of which fan is labeled what clears up a lot of my confusion! Once again, appreciate your assistance.

I'm happy to see this forum is still as active as I remember when I started my first DSM build 13-14 years ago. Back then, I didn't exactly do things the "right" way and life circumstance intervened before I could finish it. This time, I'm older and have a stable career and life, so trying to enjoy this project more than the last by doing things in the correct sequential order (i.e., maintenance, maintenance, then supporting modifications followed by more maintenance before any tuning).