Guide - How to wire up thermofans

[sillycar chick]

Hi Guys,
I have wired up my thermofan according to Witzls diagram, but I used the diagram I had saved to my computer pre-Mos' changes, where the thermofan +ve was coming off pin 30 in the old diagram compared to pin 87a in the updated diagram. Wiring it up this way makes my fan run constantly, does this sound right? Henc why the diagram was updated to the correct wiring? I can post up the old diagram if youre unsure what im on about but I dont want to confuse others reading this thread
EDIT: I just rewired up to the Mos-modified diagram and the thermofan still runs constantly Gerrard got me the switch out of a camry ages back at the wreckers, whats the chances its dead? I heard they were pretty reliable :-S

Also, does anyone know what temp the Toyota switch in the first post comes on/off at?

And is there any reason why I cant use both relays as 5 pin relays, and just leave the 87a disconnect on the first relay as per the first diagram in the first post?

Thanks for your help guys

[RA35GT]

Heya Silly,

Disconnect the thermo switch wire from the thermo switch. The fan should then turn on.

Then connect the thermo switch wire to ground, then the fan should turn off.

If this isn't the case then there is a wiring issue with the relays.

If it tests out ok, then your thermo switch may be the wrong type or is faulty.
To test the thermo switch pull it out and test for continuity between the body and the connector. It needs to be short circuit below the trip temperature and then open circuit above the trip temperature. (Test in a saucepan on the stove with a thermometer).

If your thermo switch doesnt operate as above, but instead is open circuit below the trip temp and short circuit above the trip point, then you have to slightly change the wiring. You just have to connect the fan + to pin 87 instead of 87a. (PS. In this configuration if the thermo switch wiring becomes detached the fan will NOT turn on. Also if the switch craps out you need to add an alternative way to turn the fan on. i.e. carry a wire link or similar)

[sillycar chick]

Hey,
The fan stays running regardless of whether I disconnect the wire going to the thermo switch or not. Its wired up as per witzl's diagram on page one and im using the same sensor he has used in that example, off a camry. It looks exactly the same as in the photo in the first post.
I wont have a chance again to test the sensor until the weekend...
Thanks for your help!
Dana

[takai]

Remember that some sensors are normally open, while others are normally closed, and they can look visually identical

[RA35GT]

Silly, does the fans turn off if you connect the thermo switch wire to ground?

As takai said, you may have a different sort of thermo switch.

[sillycar chick]

Ok, i'll check that tonight and see if its the case....

[PlacentaJuan]

i am hooking up a thermo switch (normally open 95degrees on, 90 off) and want to know how to wire it up so that the a/c will turn on the fans if the temp is <95 but it wants the fans on.

i cant work it out.

i allready have 2 thermo fans running through 2 relays, do i put the thermo switch to switch 12v or ground? how do i wire in the a/c without the thermoswitch turning on the aircon?

[RA35GT]

y0 PJ.

What you need to do is to to add another relay so the a/c and fans are isolated. (Also means you can trigger using +12V of the A/C compressor). Diagram attached dood.

PS. If you want to turn the fans on using the HP switch the wiring is a little different because the HP switch is a switched ground. (Take Pin 86 on the extra relay off pin 30 and then it needs to go to +12V and then pin 85 of the extra relay will go to the HP switch)

[PlacentaJuan]

thanks for that ^

can you do the digram with the relay symbols (insteal of just the pinouts) because i can understand it much better.

i want to wire it up to the HP SWITCH< THAT WAS I WONT have the fans running on the highway if the a/c doesnt require them.

i will do what mos suggested in an earlier post, and wire the thermo switch to switch GROUND and run it in paralell with the HP switch.

[RA35GT]

hey dood, not quite sure what you mean by relay symbols but I assume you mean show the contacts and the coil. If so, this is attached.

I am pretty sure the HP switch is a normally open switch (it is in a mkiii) but you need to confirm that on your car. (If its a normally closed switch will need to change the wiring slightly and use a different relay)

[CrUZida]

Rudi, pretty sure the mkiii is wired up with the HP switch and the TFS in parallel - ie without that 3rd relay.

I also used a single 40A relay to activate both fans.

[RA35GT]

y0 Andrew,

Yeah, your right.

If you connect to the HP switch you don't need the 3rd relay because its already isolated.

I shoulda thought of that LOL.

Thanks, will change drawing.

--EDIT--
Actually, if the thermo switch turns the fan on then the AC condensor fans would also come on if fitted even if the AC isn't on. (Going by MKIII diagrams). No biggie though IMO.

[CrUZida]

Actually, if the thermo switch turns the fan on then the AC condensor fans would also come on if fitted even if the AC isn't on. (Going by MKIII diagrams). No biggie though IMO.

Surely though if you are running twin thermo's (such as AU) then you'd remove all the stock condensor fans as they'd become redundant.

[RA35GT]

Well, I would think so, but you never know.

[CrUZida]

Haha, indeed you don't!