Guide - How to wire up thermofans

[Fish]

95 degree's turn on and turn off at 82?

[The Witzl]

If I can chime in and say that on my 2JZ (running twin 14" thermos) I am running twin relays that are switched by the Jaycar "Universal Voltage Switch" I get the signal from the Gauge Temp probe and have them turn on and off based on the signal (voltage) recieved from the factory probe. I also run a tiny led on the dash that illuminates when they are running so I can tell (as they are very quiet and almost impossible to tell once the engine is running...

No need for a "over-ride" switch as I can easily switch them on at the relays if there is any problems with them not turning on..

Jaycar link...
http://www.jaycar.com.au/productView...=&SUBCATID=347

Southo done good here

[SillyCarS]

ALSO!

Dont foret if you run two fans make sure you wack some diodes in, as this will stop any 'back feeding' of the voltage between the high and low speed fans and cause them either to lock or not operae at all. This is normal as with two fans you will want to bridge both the fan relays together, this insures the will both come on as early as possible and both drive a a constant speed

[Robbos_Toyotas]

and another thing, take note of the operation of the switch. Toyota are almost the only manufacturer to make a "normally closed" one, so the output to the fan on the relay will vary depending on this.

[bansheebuzz]

sorry dont worry was not supposed to post

[Mos]

ALSO!

Dont foret if you run two fans make sure you wack some diodes in, as this will stop any 'back feeding' of the voltage between the high and low speed fans and cause them either to lock or not operae at all. This is normal as with two fans you will want to bridge both the fan relays together, this insures the will both come on as early as possible and both drive a a constant speed

Are you serious?
Not sure what you're trying to say here, but I haven't seen any fans that would need that.
I think you might mean that the fans have two windings, one for low speed and one for high speed, in which case you would need to make sure you don't feed both windings are the same time - this is not the case with any fans that I have seen used in automotive applications, and I'm pretty sure none of the fans discussed in this thread are of this type.

The low speed / high speed modes are effected by running the two fans in series for low speed (so each fan is supplied 6-7V), and conventional parallel operation at high speed (each fan gets 12-14V).

The suggested diodes would need at least 20A current handling, something which is only commonly available in a large bridge rectifier rather than individual diodes, but as said above, they're not needed in my experience.

and another thing, take note of the operation of the switch. Toyota are almost the only manufacturer to make a "normally closed" one, so the output to the fan on the relay will vary depending on this.

I used to think this was a toyota standard (NC temperature switches), until I saw the IS200 diagrams - the temperature switch is a normally open type, so it's possible more modern toyotas will vary.

Mos.

[PULSE]

Hey guys, sorry for bringing up an old thread and asking a noob question but would someone be able to tell me what relays to ask for when I go into jaycar. Also what size fuse should I be using between the battery and relay?

Cheers, Matt

[takai]

SPDT or "Horn" relays.

[PULSE]

I bought 2 horn relays the other day, one was to use as my EFI relay, the other was meant to be for this (thought I only needed one), but they are only 4 pin, not 5 pin as in the diagram?

[Cuts]

hey all interesting read.

since a number of you are more electronically minded then me i thought i could ask you chaps a question.
the thermofans in the 205 have stopped working properly, they switch as they are supposed to but the fans go around at about 5 rpm (both fans come on togther), the fans are fine, the temp sensor is fine, at the moment i ran new relays and wiring for the thermo fans but if possible ide like to have it back to the neater stock setup.

any thoughts on why they would be turning so damm slow? earthing problem? Me and a mate tested one of the fan outputs and i seem to remember the voltage dropping from 12 straight to around 2 or 3 when it was on load, hence the slow turning i suppose.

Im 99% sure the relays are firing as they are supposed to.

cheers in advance.

[VA61DETT]

Cuts, Did your new relay setup work ok?
If so then it most likely would be the factory relays are stuffed / contacts burnt perhaps?
You may be able to disassemble them and clean the contacts, but best to replace.
Should be able to measure a very low <1(ohm) resistance to ground on one of the fan plugs (from car side)
this may not always be the case if there is some fancy speed control circuit, not too familiar with pug wiring.

I just finished installing one of the jaycar voltage switch kits on my MA61, works a treat with the factory temp sensor,
also modified it to allow staged switching of 2 fans (using leftover op-amp), to help with sudden inrush current.
If anyone is interested I can post the whole setup + pics & circuit diagrams.

-A

[LeeRoy]

anyway, to do this is use a normally open 2 wire thermo switch, as is easily sourced from the bottom rad tank of practically any 90's mitsu magna. on at 85 and off at 75 if i remember correctly

secondly, if i run two fans, i run them on two independant circuits, with their own relays etc, just incase sommething fucks itself

Is a 2 wire thermoswitch wired up differently to a single wire one? and how do the 2 wire versions work?

[Cuts]

va16 yeah my new relay setup works fine, but its just masking the problem.
we did test voltages on the relays contacts in the fusebox, and relay one can fire relay 2 and 3 like its supposed to.
see the thing is the fans turn on and off when they are supposed to but they are only just going around, not at full speed like Mr T intended wayyy back in 94.

[PULSE]

I got a few relays and a fuse holder so I'm going to have a go at wiring it up today. I'm still not 100% on a few things, first of all, what size fuse should I be using? In the diagram is the top pin the one closest to the front of the relay(ie the part with the writing/diagram on it)? Theres another image in the original post that doesn't load anymore, has anyone saved it?

Thanks guys!

[VA61DETT]

Cuts - Still sounds like your origional relays are flakey to me, they may be turning on but the 'on' resistance of the contacts may be high, hence the large volt drop on the fan side.
Could also be fan fuses / holders having contact issues, are you able to swap out the fan relays with some other ones, or may be just bridge the contactor socket with a bit of wire (as a test).

-A