Thermo fan/sensor/Air con? - electrical fault

I'm a bit puzzled with what's going on,....

I assume that when you say you 'hard wired' it, that you pulled the active line of the existing relay line to GROUND via a switch. In doing so by default, you're also pulling down the output of the ECU that controls it,.. might not be an issue as the output may be a floating one. Regardless, it doesn't make sense that the thermo then switches off as there's nothing else that could interfere with the control line that you've pulled to GROUND. The other side is permanently at +12v.

There should be no need for separate relay,... etc,.. as Garth suggests.

The way I did this in my VP rather than chase a suspect temp sender for the moment was to put in a SPDT switch that operates in a manner that if its OFF it let's the ECU control the thermo and when ON, it BREAKS the ECU line and forces the relay control line to GROUND. Simple install, all inside the cabin with low power wires. Just locate the line from the ECU, cut it and extend both wires to wherever you decide to put the switch. Wire things as follows: middle pin goes to the relay end of the wire you cut, one side of the switch goes to the ECU end of the wire and the remaining pin on the switch goes to GROUND.

Jim.....

 

What I did was this, apologies for the length, but I wasn't sure if you understood the 1st time.

Anyhow,....

Before you begin, turn your ignition OFF,... and whatever else you feel is safe to do,.. chock the wheel if you like to also ;-)

1. Go to Dick Smith, Jaycar, whatever is closer, get yourself a SPDT switch, it should have 3 pins on it. Basically you can switch it one way and the other, i.e. it doesn't stop in the center, its NOT a center OFF.

2. Grab a Gregory's, find out what color wire you're interested in ?

3. Locate that wire at the ECU, i.e. where all loom plugs attach.

4. Cut the wire, leaving enough between the end of the loom and the cut for you to work with. Crimp a connector at each end, those bullet type are fine for this.

5. Get yourself some speaker wire or whatever, so long as its 2 core, long enough to get to your cut and wherever you decide to locate the switch. Route it within your dash/console, etc,.. so its in place. I put mine under the right switch bank on the dash cluster.

6. Crimp a suitable connector onto both strands at the ECU end of your bit of 2 core. One of each gender of bullet crimp. This means you can always go back to factory easily if you need to and remove everything.

7. Get another 3rd bit of wire, a black one, ground one end and route the other one to your switch.

8. Connect the 3 wires as follows:
a) One end of the switch goes to the end of the wire that connects to the ECU.
b) The other end of the switch, goes to the black one that goes to ground.
c) The middle pin of the switch goes to the remaining wire that connects to the wire that goes to your relay.

Done.

With the switch in the OFF position, the ECU has control and does whatever it tries to, just as it does now. Toggle the switch and you effectively disconnect the ECU from the picture and FORCE the relay ON, hence turning on the thermo.

Cheers,

Jim.....

 

Cool. No problem. Hope you get it all sorted before the warmer weather kicks in.

If you do get the kit, I'd be interested in the schematic,... in reference to its hysterisis control.

Cheers,

Jim.....

 

Hi all,
just thaught I would add a little something to the thermo fan issue, my fan stopped working and obviously the temp would rise, but when the A/C was on the fan would work, after checking fuses relays etc, I finally found a blue and white wire directly under the blower relay, i spliced into it and attached an earth wire whitch I grounded to the steel housing of the under hood fuse box , and presto the fan works good now, so in conclusion I think it was just a bad earth on the fan relay.
Regards kirk