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Thread: '91 4 Runner Thermal Fan ?

  1. #1

    '91 4 Runner Thermal Fan ?

    Can someone help me with how the thermal cooling fan (12Volt) on the radiator is wired to operate? Recently purchased a ’91 model diesel and tried to get the fan to operate on the weekend without luck. Traced the wiring from the fan as best I could through the loom and found it connected to what appears to be a series resistor fitted to the passenger side bottom of the radiator. This resistor? had a broken terminal so off to buy a replacement today and hoping that this gets the fan to operate. Found the fuse for the fan marked CDS Fan and there are 2 relays fitted adjacent the fuse however not sure of what controls these relays, temperature, A/C etc?

    Quickly connected the fan straight across the battery and it works fine, so understanding what controls the fan is the issue.

    It would be nice to get the fan to operate to ensure that it does function however need to understand the correct operation otherwise I may be chasing my tail.

    Any help would be appreciated.

    Regards

    Cameron.

  2. #2

    Re: '91 4 Runner Thermal Fan ?

    There are a couple of ways that these fans operate. I assume that you have an engine fan being driven from your engine? If so, it is probably there for your air conditioning.
    They are usually set up in one of two ways.........
    One way is that they will be wired in with the A/C switch and when the A/C is operating, it will automatically come on and stay on whilst the compressor for your A/C is operating.
    The other way that they work is with a high pressure switch. You can probably find it on your receiver/dryer(little tank looking thing with a pipe coming out either side) and if you bridge the wires on the connector, it should make the fan cut in. If your switch isn't on the receiver/dryer, you will be able to find it either on the back of the compressor, or just follow the small A/C line between your condensor until it disappears into the firewall.
    I like fishing

  3. #3

    Re: '91 4 Runner Thermal Fan ?

    Yes, have the fan coming off the engine so assume that the 12 volt fan would be for the AC. I found another resistor block at the wreckers this morning so will fit and see if the fan starts when the AC is running. If not I remember seeing the high pressure switch on the AC drier so will start looking back from there.

    Thanks for the tip.

  4. #4

    Re: '91 4 Runner Thermal Fan ?

    Most likely case is that it runs the same as a Diesel Surf is set up.

    There will be a fan for your a/c, and then a second 12v fan for an overheat protection.

    The surf i have had the a/c underslung, so it had its own two fans on it. There is a clutch fan run off the motor, but then a 12v thermo fan that cuts in above a certain temperature (not sure exactly how high). The only time you'll have it cut in is when the water temp triggers a switch.

  5. #5

    Re: '91 4 Runner Thermal Fan ?

    There seems to be only one 12V fan that I can see, however might need to have a closer look on that. You have me thinking a little know, there is 2 x CDS (whatever CDS means ?) relays fitted so perhaps there is one 12 V fan for the AC an another for the water temp.

    Need to have a closer look as the 4 Runner and the Surf seem to look very similar.

  6. #6

    Re: '91 4 Runner Thermal Fan ?

    Try this.....

    http://www.toyotasurf.asn.au/techsit...0for%20all.doc

    its from an ln130 but should also work for yours.

    C.J.

  7. #7

    Re: '91 4 Runner Thermal Fan ?

    Thanks for the document, it helps to understand it a bit more.

    Regards Cameron.

  8. #8

    Re: '91 4 Runner Thermal Fan ?

    You got it working yet Cam.
    If not try an earth lead from your car body to the radiator, hook it up to a brass plug or fitting down the bottom of the radiator.

    The radiator is insulated from the car body with all the rubber mounts, sometimes you just need a bridge wire and all is well.

  9. #9

    Re: '91 4 Runner Thermal Fan ?

    Well, I stuffed around with this fan for a week. Wanted to try to understand how it was supposed to (wired) to work and get it going from there. Ended up buying one of those workshop manuals which had a wiring diagram in the back, only to find that yes it sort of showed how it was wired but omitted the detail just where it counted. Next was to try and trace the wiring via the cable looms and colours, not an easy task when all those colours blend into one after a while. Tried bridging out the contacts on the relays, no good, tried shorting out the presssure switch on the A/C, no good, tried running the motor for a long time in the hope that the water temp switch had something to do with it, no good. What I did find was the fan has a 12V+ wired direct to it from the fuse box in the engine bay. The negative wire from the fan goes through the CDS Relay 1 then down to the resistor block on the condenser,away into the cable loom and off ??. So basically the control circuit for the fan works on a switched negative.

    So, fed up with wasting time on how the fan is or suppose to work decided to fit my own relay wired to a switch on the dash labelled 'on' and 'off', wire from the relay to the fan on the condenser and works a treat. Next step is to wire from the compressor to the relay so it operates automatically from the AC or manually from the dash, which is as described in the link provided by GBC above.

    Thanks for the help on this.

    Regards Cameron.

  10. #10

    Re: '91 4 Runner Thermal Fan ?

    Cam I drove me Cordia turbo with out the A/C fan working whilst the A/C was running. But it ran with the thermo cut in from the radiator.

    But anyway it didn't hurt the A/C at all, even when I asked the A/C guy at work he said it would make bugger all differance.

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