Outback cooling fan manual switch and light indicators

teki1975

Forum Member
Joined
Jul 14, 2015
Messages
61
Location
Hobart
Car Year
1998
Car Model
Outback
Transmission
Auto
I have been considering installing a manual switch on the dash wired to the main cooling fan and indication lights to tell when the cooling fans are operating. My only concern is will installing such a switch and indication lights play havoc with the ECU has anyone else ever attempted this.

Currently the ECU controls the radiator cooling fans I guess I would just like to have manual control over this instead of the ECU. Any I:question::question:deas
 
There's probably an easier way to do it and I'm interested in finding out - but years ago I added a set of relays and broke into the circuit near the fans. The switch is on my centre console.
 
What do you want to do ? Turn them on early, or keep them off ?

I don't think the ECU knows or cares if the fan relays are actually engaging.
 
duncanm said:
I don't think the ECU knows or cares if the fan relays are actually engaging.
Click to expand...

^ Correct.

BTW - my setup is to turn the fans off e.g. for water crossings.
 
duncanm said:
What do you want to do ? Turn them on early, or keep them off ?

I don't think the ECU knows or cares if the fan relays are actually engaging.
Click to expand...

I want to be able to them on early I was thinking of going direct from ignition for the power and have a switch that can be turned off and on to operate the primary fan. and connecting two diodes one for low speed wire and one for high speed wire place these in series before I tap in to the two fan wires this should stop and voltage reading flowing back to the ECU. ?
 
Why do you want to turn them on early ? No matter..


Do you have speed controlled fans or simple on/off ?

For simple on/off - I would suggest you wire in a relay in parallel with the OEM fan relay to pull the fan 'power' to 12V, and control that with a switch.

That way, you don't muck around with the ECU output wiring directly. There are diagnostic trouble codes for the fan outputs -- so I'm guessing the ECU does at least monitor the fan control signals.

The other alternative, which I think is what you're suggesting, is to put a new relay control wire in parallel with the ECU one, and isolate them with diodes to prevent the ECU seeing the fiddled relay control line. This should work fine.

Code: 
ECU --------|<---+---- Fan Relay
                 |
GND --- /---|<---+

where '/' == switch
 
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