Guide - How to wire up thermofans

[Mos]

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?

20, 25, 30A Toyota uses 30A (each) for fans that draw around 6-7A continuously. Fuse each fan individually and use individual relays. Even though the 6.4mm spade connectors are nominally rated at 15A, one such connector generally will not handle two fans (12-14A) in the long run.
Fuses are there to protect wiring against short circuits, so the exact rating of the fuse is not critical - generally I choose a fuse rating no higher than the thinest cable supplied by that circuit (ie 20A cable, I'll use a 20A fuse, assuming the relay can handle 25A or so, although it's not that critical). You could get a failure mode where the current exceeds the rating of the cable but is within the rating of the fuse - the wire will get hot until it either burns or the fuse blows or you notice it. A straight short circuit will blow the fuse almost instantly, so even a 10A cable won't get very hot before a 30A fuse blows.

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)?

If I'm thinking of the right one, it's pin 87.
Key points to remember:
1) 85 and 86 are the coil of the relay and as long as you apply power to those it will switch on - it doesn't matter which way around so you don't have to follow the diagrams to the letter.
2) 30 and 87 are the switch, and it doesn't matter which way around you connect it (in certain circumstances it will matter if you have 3 switching pins, ie either 30 and two 87 pins, or 30, 87 and 87a).

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

It can be. A thermo switch can either connect or disconnect when heated. A single wire switch has to have the body grounded so you would need to use it in the ground path of the relay switching.
A 2 wire sensor can be used in either the ground path or the power path for the relay switching. In practice I think all toyota sensors are in the ground path, regardless of type.

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.

Keep testing. Measure voltage, with the fans running, across every connection - ie measure across the length of wire from the relay to the fan; measure length of wire from fan connector to ground, and relay to ground; measure from battery to both sides of the relay; measure across relay; measure the jumper wire between the two relays. If you're only getting 2-3V on the fans there is a voltage drop somewhere that shouldn't be there (well duh) - you will find it this way.
It could be something as stupid as oxidation on the contacts (replugging the plug usually clears that - have you unplugged everything and plugged it back in?) though with high current circuits it's usually unlikely as the high current burns off the oxidation; it could be corrosion in a crimp, or burnt contacts in the relays, etc.

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.

Sure, put it up - I'm sure it will be useful and at worst you'll get +rep for it

Mos.

[Cuts]

bump.
still searching for the dramas, but ive been thinking about getting some sort of thermo switch so i can change the on/off temps, as the factory ones are 94/90 i think, ide ideally like say 88 on and 84 off as the thermostat is 77deg.
question is who makes/where can i get such a switch? im not going to use the ghetto thermocouple probe ones, something i could screw into the radiator where the stock thermo fan switch is would be ideal.

suppose if there is a switch thats the temp range im after in another car i could get one of those and wire that in with relays to do the job.

[takai]

http://www.toymods.net/forums/showthread.php?t=5125

See here. Complete listing of Tridon temp senders.

[Cuts]

cheers takai,

[Mos]

bump.
still searching for the dramas

Have you done what I suggested?

[Cuts]

yes and no, ive been through it roughly, ill have another proper crack when i next have some free time, cheers for everyones help so far.

[Mos]

You know there is a diagnostic process, right? Otherwise you're just stumbling on things and you'll only fix it if you get lucky....
If it's too hard, would it be easier to just replace the car?

[Cuts]

what is this diagnostic process?
im assuming you mean with the diagnostics port checking for error codes? i havnt tried because i dont expect that to work.

and the wiring diagram for that particular part of the car is the illusive RM380E which is impossible to find.

[Mos]

The diagnostic process is the process by which you come up with a diagnosis - ie the steps you take to work out the problem.
In this case the diagnostic process is to probe each section of the circuit to find the unwanted voltage drop.
What I took for granted, is *exactly* where to probe when I suggest a diagnostic process... sorry... I guess I just assumed that when I say "the wire from the fan to the relay" you will know what I mean.
The toyota twin thermo setup is virtually identical across the whole range, so you should be able to work out where to probe by looking at the ST185 diagram. It will at least give you an idea of what the layout is and what the relays do, but the wire colours might be slightly different. I think I had some 205 diagrams. I'll see what I can dig up.

[Cuts]

cheers man, when you said about diagnostic i assumed you were talking about grounding pins in the port like you do for engine. and systems checks.

yeah like i said i had a quick test, ill have another crack when i have some time off.

checked the tridon catalogue, that one doesnt have the sensor configuration on it, but one i looked at today at bursons had, there is fuck all on offer for a normally closed switch.
185 and 205 both use normally closed with different plugs, swtich on/off temp is the same, and they list only two on off options for a normally closed with that thread size, 95-90 and 90-85. Factory specs are supposed to be 90-85 apparently but mine seems to be more because according to the pfc its on at around 95 and off at around 90 (from memory) either i have the wrong switch or mine is a little shagged.

[Rosie]

Any reason this isn't used ( the drawing not the part #)
And FYI Champion Part # CFS 40 is 95on 90 off, M14 x 1.5 $50 new from generic places repco etc.

[CrUZida]

Any reason this isn't used ( the drawing not the part #)

You'll find those switches aren't designed to handle large current.

FWIW AU/EL thermo's pull ~15A EACH while running (as will any other decent thermo), and probably 4-6times that on startup for a couple of hundred ms.

[Mos]

Toyota fans tend to draw around 6-7A on a 30A capacity circuit... Haven't measured startup current though...
15A is huge - did you measure that?

[takai]

My twin SPALs on the old car drew >30A as it repeatedly blew 30A fuses.
The DC/DCripoff pair on the Cressy are also >15A each as they blow 15A fuse (i did use 30A wire for each)

[CrUZida]

Toyota fans tend to draw around 6-7A on a 30A capacity circuit... Haven't measured startup current though...
15A is huge - did you measure that?

I haven't personally measured it, but Pete (82MKII) has and from memory it was up around 15A each.
They also managed to severely melt a 25A fuse I had feeding the pair, so that tells me they draw more than 25A (but not enough more to blow the fuse instantly).
The 40A fuse that replaced them was fine.