A/C Fan comes on when the car is switched off??????

Post by **clarelude23** » Mon Feb 29, 2016 9:54 am

I don't have a service manual...any manual iv checked online is US spec and the fan timer doesn't seem to be there. Does anyone have a pdf to a UKDM manual or does anyone know the location of the fan timer unit? I had a quick look yesterday and couldnt find it

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Mon Feb 29, 2016 1:23 pm

Just looked at the USDM manual.

Cooling fan control is 10-12. As you say, no delay unit shown. Cooling fan is switched on (from a purely coolant temp perspective) directly by the rad fan switch, no feed from the ECM.

However, there are also 2 outputs from that schematic that need to be picked up elsewhere (ECM and the A/C fan diode).

On page 11-20 you can see where the ECM output goes to (ECM pin A27). This is where the ECM switches the fans on/off (by grounding that input, or not). I presume this is activated when the A/C is switched on (can't see any other way that the fans could be switched on for a/c). It's possible the ECM itself could incorporate a timing circuit, rather it being a stand alone module as it was on the 4g.

To confirm whether it is the ECM that is switching on the cooling fans when the ignition is turned off, the only way to check would be to diode check that pin on the ECM, straight after switching off the ignition, i.e. when your fan is currently starting up. Negative probe of a multimeter (set to diode or resistance check) on earth, positive probe onto that pin. If you have a circuit, then the ECM is switching the fan on. If no circuit, it's not the ECM.
note: The wire on that pin at the ECM would have to be disconnected from the ECM, to be sure you are only checking the circuit in the ECM itself. So, either disconnect just that pin at the ECM (leave all the others connected) or you would need to find the splice in the loom where the ECM connection is tapped from (will be a nightmare to track down).

Before doing that though, the easiest things to check would be:

Firstly that it's not the rad fan switch causing the fans to come on. To do this, when you have the ignition off/fans running, unplug the switch and see if they stop.
Location of the rad fan switch is on 10-11 (crap picture if you ask me - needing you to see through the engine!

) I take it to be on the thermostat housing???

Secondly you could also pull out fuses in turn to see which one causes it to stop running, which helps narrow down the circuit somewhat.
I suggest working in this order, to start with:
1. Fuse 45 (engine bay)
2. Fuse 46 (engine bay)
3. Fuse 9 (under dash)
4. Fuse 33 (engine bay)
5. Fuse 32 (engine bay)
6. If it's still running now, your circuit looks nothing like how it was designed by Honda

Post by **clarelude23** » Mon Feb 29, 2016 2:54 pm

Thanks for that reply. I will just keep working on tracking it down. Appreciate all the help guys

Post by **clarelude23** » Wed Mar 02, 2016 9:08 am

Update. I went out to start the car last night and everything was fine after I ran the car and turned it off a few times....then it starts happening again. This is the second time everything seemed fine and then went bad again.....aggggh

Post by **clarelude23** » Fri Feb 09, 2018 9:41 am

Just to clear things up. The problem stopped all on its own. All's well that ends well.