Cooling Fans Not Coming On
Discussion
On my 1993 Chimaera 400 which is fitted with an overide switch I cannot get the fans to come on either by the overide or by temperature (let it go well over 90 to see then shut it off), have checked the relay (swapped with another) and the fuse (30A) both appear OK. Is there something else that I need to check. The fault initially showed as intermittent but is now permanent. Appreciate any advice on the problem.
I would have thought that the over-ride switch would have over-ridden and therefore eliminated the otter switch. 
IIRC, you can check the fans and the otter switch by removing the otter's connector plug & shorting out the terminals (not done it myself, might be worth checking in the bible first!)
IIRC, you can check the fans and the otter switch by removing the otter's connector plug & shorting out the terminals (not done it myself, might be worth checking in the bible first!)
The otter switch is I believe at the bottom of the swirl tank on the earlier cars. If you are shorting this, paper clip or spade fuse are good get you home emergency measures, then it is not the otter. As suggested check all fuses and relays, is everything else electrical working? If all else fails consult the bible.
Al.
Al.
The Otter switch may be faulty but the overide shorts this out, I have further checked all the fuses I have a 40A fuse controlling the fans (and possibly the horn) and this appears fine. Yesterday I took out the fan relay and replaced it with another and the fans started working then stopped again after a 10min drive, the old relay worked fine in the headlamp relay slot so I am extremely puzzled. The horn works fine even when the fans don't. Is there any other thing in the circuit which could prevent this?? Lovely weather today too for once!!
FlipFlopGriff said:
Sometimes ours didn't come on. It was the plastic connector blocks. Now got a placcy tie on each and they have been fine since.
FFG
Spot on FFG, this happened to me a few times with my Chim also. Quite often you find the connectors have been tidied away and left sitting in a puddle of water. The contacts corrode and no power reaches the fans. I suggest you disconnect the connectors to the fans and give the contacts as much of a clean as you can. When you're done, reconnect the fans, short the otter switch and test the fans again.
Steve
Steve_T said:Yes. I had this too, although only on one fan rather than both. If you unplug the connectors and the terminals are dull and/or corroded then that is possibly the cause. I bought a set of tiny files and used a small flat one to clean the contacts up to bright new copper. Sprayed with electrical switch cleaner and reassembled and have had no further problems since. This was about 2 years ago too.
Spot on FFG, this happened to me a few times with my Chim also. Quite often you find the connectors have been tidied away and left sitting in a puddle of water. The contacts corrode and no power reaches the fans. I suggest you disconnect the connectors to the fans and give the contacts as much of a clean as you can. When you're done, reconnect the fans, short the otter switch and test the fans again.
The other thing to check for is the wiring. It's worth disconnecting these connectors anyway and then using a volt meter to see if you are getting power to the fans.
JonRB said:Me too!
Yes. I had this too, although only on one fan rather than both. If you unplug the connectors and the terminals are dull and/or corroded then that is possibly the cause. I bought a set of tiny files and used a small flat one to clean the contacts up to bright new copper. Sprayed with electrical switch cleaner and reassembled and have had no further problems since. This was about 2 years ago too.
The other thing to check for is the wiring. It's worth disconnecting these connectors anyway and then using a volt meter to see if you are getting power to the fans.
In my case it was just that they had come loose, but we cleaned them up a bit anyway.
Having tested the living daylights out of everything, I am still no further on, the over-ride switch works and puts the system on open circuit, there's no voltage at the fans, the front earths fine since it runs the lights and horns and these all work, all the fuses are fine, I am now going to test the wires at the fuse box, there's no switching sound from the relay. What actually switches the fans on is it the otter switch or does the signal come from the ECU??
A fuse supplies switched ignition 12v to one side of the coil, the other side is earthed via the otter switch. Locate the relay, locate the coil terminals, you should find ignitin switched 12v on one, the other should be isolated when the otter switch is cold, and earthed when it is hot.
I know the fans are working because I shorted the relay with some fuse wire and on they popped so I know what relay I need. I also no there is no 12v to work the relay even with the overide switch on so there's no 12v suppply getting to the relay. What do you mean by 'coil' and where will I locate the coil terminals in the fuse box or somewhere else. Appreciate help on finding the final piece of the jigsaw, am using the heater fan at the moment in town works ok but would prefer the real thing.
I'm referring to the coil inside the relay. As you probably know, there are two separate electrical circuits inside the relay: the coil circuit and the switched circuit. The coil circuit just energizes a solenoid inside the relay. The switched circuit passes through a switch which is opened / closed by the solenoid.
The coil circuit should have ignition switched 12v supplied on one terminal, with the other terminal earthed via the otter switch. There will be a fuse on the supply side; if you aren't getting any voltage here then check for a blown fuse.
The switched circuit will have a permanent 12v supply on one side, and the other side will be earthed via the fan motors. The supply side will be fused, this will be a big fuse (probably 30-40A).
The coil circuit should have ignition switched 12v supplied on one terminal, with the other terminal earthed via the otter switch. There will be a fuse on the supply side; if you aren't getting any voltage here then check for a blown fuse.
The switched circuit will have a permanent 12v supply on one side, and the other side will be earthed via the fan motors. The supply side will be fused, this will be a big fuse (probably 30-40A).
The problem is now resolved, the earth return was not working. I connected a new wire from the earth side of the otter switch (has no voltage when cold) to a nut on the alternator bracket and everything's working normally. Thanks to veryone for the advice -BTW where is the earth for this located is it the one by the drivers side wheel - I'll need to check why this is a problem everything else works fine.
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