working out a few loose ends on an MR2 and wanted to know if this setup would be OK. There aren’t a lot of documents on how the SW1,2,3 inputs on the EMU Black work other than connect to ground. If they are isolated this shouldn’t be a problem but wanted to double check
Basically I just want to know when the single pressure switch is activating the radiator fan AND be able to control the radiator fan from the ECU
Wow! What a brain teaser!
When the pressure switch is closed, ECU control of the Radiator fan is over ridden by Relay 1, and both fan Relays 1 and 2 are energised. In this state Relay 2 is grounding the A/C Condenser fan so that maximum cooling is guaranteed, however, the ECU maintains control of the A/C Condenser fan via Relay 3.
This seems to me to be a safety set up for an over pressure scenario in the A/C system.
The ECU is normally in control of both Fans when the pressure switch is open.
Hope this helps.
Thanks for the reply
Yes, that’s close to how the logic of the system works.. but not quite, there are two fan speeds
ECU states like this
CF on & FAN off = both radiator fans at half speed
CF off & FAN on = only one radiator fan on full speed
CF on & FAN on = both radiator fans on full speed
I would like to know when the ECU is NOT signaling the FAN output and the single pressure switch is closed
SW input would read ON when FAN is on OR single pressure switch is on
My question was more so is my proposed additional connection safe for the SW input on the EMU black?
Should be safe, it will never see any voltage on the ground side of the relay.
