Jump to content
SAU Community
  • Welcome to SAU Community

    Welcome to SAU Community, like most online communities you must register to view or post in our community, but don't worry this is a simple free process that requires minimal information for you to signup. Be apart of SAU Community by signing in or creating an account.

    • Start new topics and reply to others
    • Subscribe to topics and forums to get email updates
    • Get your own profile page, build reputation and make new friends
    • Send personal messages to other members.
    • See fewer ads!

    Consider joining our newsletter for the latest content updates

    Click here to register

R32 - Have Your Overheat Fan Turn On With Your A/c


Recommended Posts

Hey ppls,

The R32's (unsure about R33 or R34's) have an engine overheat fan positioned on the aircons condensor.

The engine over heat fan ONLY turns on when the water temperature reaches ~92-94degree's. The temp sender switch is located in the bottom tank driver side of the radiator.

This overheat fan does NOT turn on when you hit the A/C button.

Having the engine overheat fan turn on with the A/C allows air to pass over your aircon condensor when stationary, this improves the aircons efficiency/coolness and reduces engine temps (at the very least slows the increase in temp when sitting in traffic). This is especially critical if you have had your aircon converted to the R134a gas.

The R134a gas is not as efficient as the old R12; it runs a much higher head pressure, places a greater load on your compressor and places a greater heat load on your condensor.

Forcing your overheat fan on with R134A when the a/c is in operation WILL improve your aircon's coolness during long periods of idle or very slow speeds.

Most Aussy released cars automatically have the 'engine overheat' fan enable when you hit the a/c button.

Its required for our hot climate during heavy traffic.

Having my aircon recently serviced I decided to do something about having the engine overheat fan turn on when I hit the A/C button.

I remembered the A/C and Engine Fan relays were situated next to each other in the fuse/relay box under the bonnet.

See below pic.


I grabbed the multimeter and found the trigger on both relays which happens to be the far left wire on both relays. Do note the wiring is negative switching; the relay see's a constant battery voltage, only when the relay is earthed does it activate.

Please do check yours to ensure you have the right trigger wires.

Mine were:

A/C - Green wire Yellow stripe

Overheat Fan - Green wire Black stripe

See below pic.


I bridged the wires and presto... The engine fan turns on with the a/c. BUT the problem here is the a/c now also turns on with the engine over heat fan when the engine overheats (~92-94degree's). See below pic.


The solution to having the a/c turn on when the engine overheats is to use a SINGLE DIODE!

As the relays activate when earthed place the diode appropriately. See below pic.


So its as simple as that. Head down to Jaycar, grab a meaty diode (~0.25c) and splice it in to the trigger wires.


Be bugged wiring in another relay; this is a cheap very tidy solution.

Link to comment
Share on other sites

Good one! So the diode (one-way only) stops the A/C from seeing the fans ground? But the fan can see the A/C's ground, so it comes on.

I was keen to do something like this!

Oh, and to confirm, my 33 doesn't switch the fan on when the A/C is on either.

Link to comment
Share on other sites

All done. :D

I ended up using a little wire to position the diode away from the loom so to speak.

There's just not enough room in there.

A flux pen gives very very tidy solders as it literally sucks the solder off the iron and evenly spreads it.

I have solder with a flux core but there's just nothing like having flux on the item that you are going to solder.

I first covered the joins etc with liquid elec tape. Why? Because I had some laying around, liquid elec tape tends to go soft with heat. So its not that crash hot but does keep water out.


And now all taped up.


You can only just see a little bit of the white wire under the relays. :no:


Stoked I didn't have to bugger arse running another relay and chopping in to wires that really wasn't required.

Remember your all smart individuals, its up to yourself to perform your own research and decide IF you should attempt this mod. I'm not going to be responsible for you breaking something. :yes:

Link to comment
Share on other sites

I have been thinking the same thing Cubes, and the same issues (S2 97' GTST) Has anyone worked out yet what relay/pins the R33 fan runs off? I was just going to splice in my own relay/find a spare and have a switch to manually turn the fan on.

Link to comment
Share on other sites


If you have both the A/C and Rad/Blower Fan relay on your fuse/relay box then you will be able to perform this mod. :yes:

Have a read up on automotive relays, from what I've read automotive relays are usually negative switching.

It really is easy, have a play with a multimeter for a while, you can't short or blow anything up testing with a multimeter so fear not. :D

Link to comment
Share on other sites

  • 2 weeks later...

I'm planning on hooking my thermo fan up to this, so I tested the on/off temps last night (via CONSULT), so for the record on my R32:

*** The fan switches on at 91C with a 3C hysteresis (i.e. off again at 88C). ***

Link to comment
Share on other sites

  • 2 weeks later...

When you say it "stays on", you mean after you turn the AC off, yes?

The std Ran fan is attached to the engine, so it's obviously, always on.

As for the AC one, remember it's an overheat fan, so your car could be running at 91+C and triggering the fan that way.

But don't be scared by the word "overheat", 91C is fine (your temp needle in the instrument cluster doesn't hit "Hot" until closer to 110C), it's just used to help out the clutch fan in hot weather etc.

Link to comment
Share on other sites

Easy way to find out.

Hit the a/c button and the fan should 'instantly turn on.

If its cycling in and out when the a/c isn't then check engine temps and you may very well find that is whats activating the engine overheat fan.

Link to comment
Share on other sites

Yes.. Run a wire from the rad fan relay in to the cabin, in to a switch and then earthed. (remember the relays are negatively triggered)

But why would you want to do that?

Just have it activate when you hit the a/c switch like aussy cars do.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Latest Posts

    • Hi, This thread will possibly get deleted, but genuinely wanted seasoned veteran feedback on an R34 GTR price. Saw the below listed recently on CS for a mouth watering sum. With the amount of work done to it, is this considered a fair price? Or is it still heavily influenced by what's going on in Japan and the upcoming US market, on top of the modifications? At these rates, this is a nice goodbye to the average Joe's dreams. Even if it were listed at half the price, that is still a lot of hard earned cash. Every month, the dream goes further towards the moon. Have to become a successful business owner to even come close 😁   PS. If the owner is here, no offense! You do what you gotta do!
    • - R32 GTR ABS Control Unit. R32 GTSt Parts . . . - Front Side Lamps x 2. - Brake Master Cylinder. Fully Reconditioned. - Relays.  Many different types.  Also applicable to other models. - Coil Packs. - Air Con. Control Unit Panel.  Also a unit for an R34. - Rear Window Demister Electrical Filter Unit. - ECUTalk Unit + cables + plugs + s/w CD.  Works with R32 GTR. - Boost Gauge.  Auto Meter.  Fits any car. - Center Wheel Caps x 4.
    • Have you tried searching this site? Search bar is at the top right of the page
    • If the timing check shows timing bouncing all over the place despite commanding a fixed value in the ECU then the most likely explanation is either the CAS drive pin on the cam has worn, the CAS drive gear has worn, or both. I suspect a number of the more severe cases of timing scatter are actually due to this issue.
  • Create New...