1993 Mirage / Lancer Or Possibly Proton Wira Cooling System Wiring

[The Don]

Guys, I need some help with the colling system wiring of my 1993 Mirage.

Basically yesterday while I was driving back the temperature shot up and boiled. I discovered the issue was that the radiator fan was not working.

While I was investigating the problem I realised that the wiring of the fan was a bit of a mess. And because the fan was changed (possibly a couple of times but I changed it 6 months ago due to broken fins) and the wiring was modified (possibly by the AC guy a couple of years ago) I was at a loss to figure out how the damn thing should work.

From what I can figure the thermosistor switch in this car is in the radiator in the bottom. It has two wires but only one is connected to anything, the other was blanked out using insulation tape. Something is not right there. I haven't figured out whether the termosistor switch works anymore or not.

The fan connector (no gurantee this is original but could be) seems to have three wires coming out of it. The fan sees to need only two but of course this is not the original fan. The thermosistor switch has a 2 wire connector.

When I found the circuit the thermosistor switch had one wire joined up with the ground of the fan directly though there was nothing connected to the other end of the thermosistor switch. The positive wire was connected to one of the wires in the fan connector and one wire of the fan connector is not linked to anything.

A neighbour helped me a bit and he figured that there were two ground wires and one positive in the fan connector (at least now, remember wiring could have been altered at the other end) and if the fan is connected to one (coloured) ground wire and the other positive wire (this wasn't how I found the circuit but this is what we figured) connecting the battery negative to big ground wire on the fan connector seems to start the fan. Now this could be the wire the thermosistor switch is supposed to connect to but as I said before it had only one wire connected to anything.

But the radiator fan should also come on when the AC is on with the condenser fan. That does not happen. I have found one positive wire that was lying around again not connected to anything that comes on when the AC circuit is on, so this could be the missing link, but I am not sure where its supposed to connect to.

From what I understand the radiator fan should work in the following way. If the water temperature is above 85C the themosistor switch will complete the circuit and turn the fan on. When the AC is turned on another relay also triggers the radiator fan on.

I have found this circuit diagram for an older Mitsubishi but assume it could be similar in my car as well. There are 3 relayes in my setup as well (on the far side near the front headlamp).

http://manual.pajero4x4.ru/?wpfb_dl=3571

Could somebody confirm that the setup is the same in later Mitsubishis (1993) and could someone please explain connections going into the radiator fan motor, just to confirm what I've assumed.

Thank you!

[The Don]

Ironically I managed to wire the circuit properly and now the radiator fan seems to work properly. It comes on when the radiator heats up as well as when the AC is turned on.

The thermostatic switch seems to be a bit iffy. It turns on only for about 2 seconds and then cuts out and the temperature seems to hold (this is with the AC off). Is this normal?

[The Don]

Seems either the guys familiar with car electrical systems and Mitsubishis of this vintage are either completely confused by my description or are still on holiday Anyway the fan now works fine. Did a test run, temperature holds stable with AC on or off.

[Davy]

Glad you were able to diagnose the issue. Looks like you were able to tighten some loose ends of the circuit (like figuring out the wire from the AC relay) while you were at it as well.

As for the coolant temperature switch, does it still iteratively keep turning off after about 2 seconds of operation? Doesn't sound normal to me however. According to the manual, the switch should turn on at 85C and go off at 78C. 7C in 2 seconds sounds a bit off. Better get the switch checked out.

About there being 3 lines on the fan connector, I assume this is a replacement fan which was meant for a Mitsubishi with a fan control unit. The additional line should be the line that supplies current for the fan to run on a lower speed.

[The Don]

Glad you were able to diagnose the issue. Looks like you were able to tighten some loose ends of the circuit (like figuring out the wire from the AC relay) while you were at it as well.

As for the coolant temperature switch, does it still iteratively keep turning off after about 2 seconds of operation? Doesn't sound normal to me however. According to the manual, the switch should turn on at 85C and go off at 78C. 7C in 2 seconds sounds a bit off. Better get the switch checked out.

About there being 3 lines on the fan connector, I assume this is a replacement fan which was meant for a Mitsubishi with a fan control unit. The additional line should be the line that supplies current for the fan to run on a lower speed.

Hi Davy,

As far as I can figure, the fan only runs at one speed (at least there is no current wiring to support a dual speed operation). The fan seems to come on at 85C and then run for about 5 seconds and then go off and then come on again. I must admit its possible that the fan now fitted is a more powerful one than that was originally fitted as the wiring coming out of the fan are thicker than the wires in the car.

As for the 3 wire connector, I figured out how it works. Basically there were two wires broken for some reason which had caused the fan to fail.

The first wire is an always on negative wire which comes on with the ignition. The second is the positive wire which is supplied from the fan control relay. There is another wire that is mated to this one which is from the air conditioner control relay which supplies power to the positive wire when the ac is on (this by pass wire was broken, its possible the current wiring of the bypass circuit was modified at some stage due to some issue but it still works as it should). The third wire is a negative wire that feeds into the relay through the thermositor sensor switch which turn the fan control relay on when powered

So the fan connecter has one wire (negative) going into the thermisistor sensor switch and the wiring coming out of the sensor is also connected to another terminal in the fan connector which arms the relay and turns the fan on.

The only drawback of this wiring system is that there is no fail safe. If a wire fails the fan will never come on. In some cars like my old mazda if the wire from the thermosistor switch was to break the fan just comes on and is always on. But this is how the Mitsubishi system works and confirmed by the wiring diagram.

So for the moment I'm going to assume the 5 second operation is normal as the temperature remains stable.