I have been unable to make the Auxiliary Fan Mod work.

I bought a 4 pin relay and grounded Pins 30 and 85.

I connected the Red/Brown wire at the black relay, which is the one closest to the passenger on the passengers side to Pin 87.

I connected the Green/Brown wire at the blue relay closest to the front of the car on the driver's side bank of relays to Pin 86.

What happens is the auxiliary fan comes on regardless of whether the A/C is on or off. If I disconnect the ground wires, the relay, or one of the two remaining wires, the fan goes off.

If I leave everything connected, the fan still runs after I turn off the car.

What am I doing wrong?

I tried switching the relay with another relay on the car, without any change.

 

I am not sure that the 'blue relay' you are using for the feed IS a relay that is switched by anything related to the fan. The fan needs to be switched by something temperature related or ignition/aircon-on related. It sounds like you have found an always live feed.

Could you explain exactly what you are trying to achieve with switching of the aux fan?

Greg

 

I'm trying to follow a (seemingly) popular modification where the auxiliary fan will come on either (a) when the coolant temp sensor reaches a certain temp (OEM setup) OR (b) when the A/C is turned on, regardless of coolant temperature.

The idea was to wire the aux fan switch wire and the compressor clutch switch wire and tie them to a relay.

I have attached the wiring diagram I found elsewhere on this forum.

 

I have my aux fan wired to come on with the aircon compressor. As standard on my model, the aux fan used to come on, as you want it to, either with the temp switch or with the aircon. So if the aircon was switched off the aux fan would still come on if the switch in the water pump housing closed.

The OE system uses a diode pack to achieve this, ie, if the fan is wired to come on with (eg) the temp switch, the system does not backfeed current to start the aircon unintentionally. I think all you need is a diode stuck into the system as follows:

Run a wire from the aircon compressor feed to splice into the wire that comes FROM the temp switch (ie the wire that goes live when the temp switch closes, NOT the wire to the switch that is always live when the ignition is on). In this new wire, before it joins the temp switch wire, put in a diode that will stop current backfeeding to the aircon compressor if the temp switch closes. I use a small connecting block with screw-down fixings to put in diodes. A diode is a "one way" current device that allows current to flow only in the desired direction (apologies if you knew that).

Then the aux fan will come on as you desire, either because the aircon is on, or because the temp switch has closed. And one working will not start the other, if they are both on, also OK. In addition the aux fan will, if the water is hot enough, continue to have its after shut down running on capability.

AS my car is a 1985 and I have no experience of a 1996 car, it may be that your basic fan wiring system is completely different, but I do not think it is. I am sure someone more knowledgable will swiftly correct me if I am wrong!

Greg

 

I have attached the wiring diagram I used to make this happen.

Well almost. This looks like a wiring diagram I used, except for that note "new relay ground" at the Blue Brown wire. (UN)

I just ran the new relay grounds to an actual ground point. I know the ground works because it runs the fans, but does anyone know if it makes sense to run the ground wires to this UN, or blue/brown wire?

The previous wiring diagram did not have that note. I can't tell if they used the UN wire for convenience since its found at the convenient compressor clutch relay.

Any ideas?

Thanks

 

Seems to me that the red/brown wire has 12v+ at all times, thus energizing your added-on relay.

I'll do a little digging

Cheers
DD

 

Yes! It definitely appears to be hot all the time, even with the engine turned off!

Should I consider grabbing the wire directly from the compressor itself?

 

I'd be more concerned as to *why* that wire is hot at all times. It surely shouldn;t be. Is the compressor relay stuck?

FTR, the wiring scheme for the compressor is different on a '96 (versus the '94 diagram you're working off of). At first blush, at least, I don't think the differences would change your modification in any way....but it might merit more mulling at some point.

Cheers
DD

 

I swapped relays without any change in the way things worked, so I don't think the relay is at fault.

I'll do a little more investigating to see when the wire goes hot...

Thanks

 

I think that the fan is supposed to run for about a minute after you switch off anyway.

 

It was still running a full 5 minutes after I turned the car off and removed the key. I disconnected the relay at that point. I didn't think that it was going to deactivate on its own.

 

I dont see the point in the AC mod. From my experience my need to cool off comes a lot later than the V12s.

If by "blue relay" you mean the diode pack on the left side fender, then you are on the right track.
My fan relay is still in place and plugged in.
My temp sensor has a jumper on it.
There is another jumper at the blue diode pack. All of these wires are green, so you have to play with them at risk of replacing the fuse for the horn/headlights.

No idea how it is wired, I just know after the diode pack went out and I played with a jumper for a minute, I was able to make the fan turn on with the ignition.

EDIT: Make an actual jumper with spade/bullet connectors crimped to a wire and connecting two things together. By jumper I do not mean clamps or a loose wire wrapped around ends of terminals.
My car has been running for a year like this. Tuck the temp sensor wires away and it looks neat. Replace the diode pack cover and it looks neat as well.

 

Yes, IF the coolant is hot enough to close the temp switch. Otherwise, no.

Cheers
DD

 

All fine and well but the subject car is a 1996. The later cars don't have the diode pack. The aux fan wiring scheme is quite a bit different from the 80s/early 90s cars.


Cheers
DD

 

I'm attaching the wiring diagram for my car.

I will do some more investigating on why that RN wire is hot seemingly all the time?

 

Since the relay isn't stuck I can only guess that the a/c control panel/module is somehow sending an "on" command at all times

Cheers
DD

 

My mistake!!
sorry I don't have a 2 cents in that case, hope you figure it out mate!

 

Problem solved. The other line diagram had the contacts reversed. I can confirm that this mod works on the facelift cars if you do the following:

Ground pins 86 & 87.

Tie the Red/Brown wire that goes to the relay on the passengers side (furthest from the passenger) to Pin 85

Tie the Green/Brown wire that goes to the relay on the drivers side (furthest from driver) to Pin 30.

Bingo.

Thank you all for your help!