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by **LEAKER** » Sun Jul 03, 2011 6:38 pm

So sometimes my cooling fans work and sometimes they dont. Obviously this is when the car is up to the correct temprature. Any common faults or ideas on where to start fault tracing. It has 2 fans and neither of them are kicking in so im thinking its an issue with either the wiring or the relay.
The fuse box has seen better days and the wiring is in fairly poor condition.
THe temp sender has been replaced

Ideas??

by **Boosted_162** » Sun Jul 03, 2011 6:48 pm

LEAKER wrote:So sometimes my cooling fans work and sometimes they dont. Obviously this is when the car is up to the correct temprature. Any common faults or ideas on where to start fault tracing. It has 2 fans and neither of them are kicking in so im thinking its an issue with either the wiring or the relay.
The fuse box has seen better days and the wiring is in fairly poor condition.
THe temp sender has been replaced

Ideas??

The 2nd fan is aircon iirc, hence it not turning on when hot.

by **LEAKER** » Sun Jul 03, 2011 6:50 pm

i dont run aircon. have my aircon fan hooked up to feed of my engine cooling fan and both of the fans run sometimes and then both of them dont other times.

by **Lloyd** » Sun Jul 03, 2011 7:01 pm

Is the engine overheating? If not then what is the problem? The fans aren't supposed to run all the time

by **LEAKER** » Sun Jul 03, 2011 7:10 pm

it's not "overheating" but the fans normally kick in with the temp gauge showing just under half and the gauge got up to nearly 3/4 before without any sign of the fans kicking in.
The problem is i've just spent 8g on an engine rebuild and i'm not going to have my engine cook again bacause the fans arent working properly so i'm trying to take all precautions

by **CelicaGT8** » Sun Jul 03, 2011 8:11 pm

Replace the sensor, fuse, and relay to be sure. R u sure you dont have a blowen headgasket?

by **LEAKER** » Sun Jul 03, 2011 8:24 pm

when i'm driving it it's fine. i got a mechnic to do a full engine rebuild and they decked the block, skimmed and tested the head, steel head gasket fitted. It's not overheated since,no signs of it pushing water out, no oil in the radiator. just creeps up a little when I sit it at 3000rpm or so to try and get the fans to kick in.
The problem i am trying to fix is fans not working when they should. But only sometimes. Other times they kick in perfectly.
I've replaced the cooling fans relay. Might try the fuse as you said just incase :S

by **loudstealthGT-Four** » Sun Jul 03, 2011 9:21 pm

your rad fan should only run when your water temp gets to a certain temp, if it not running then its not hot enough to kick in

by **LEAKER** » Sun Jul 03, 2011 9:58 pm

argh. Understood. I'm not an amatuer i understand how cooling fans work. It's getting hot enough!! Point being that once it's hot enough they're not always working. I.e it has an intermitent fault ffs.

by **CelicaGT8** » Sun Jul 03, 2011 9:59 pm

Radiator checked? why did it need a rebuild? Radiator not partly blocked, perhaps around where the sensor is?

by **LEAKER** » Sun Jul 03, 2011 10:04 pm

put new radiator in when the rebuild was done and new sensor. Needed rebuild because the cooling fans didn't kick in when i was sitting in traffic on a hot summers day and cooked the head gasket

by **rollaholic** » Mon Jul 04, 2011 8:12 am

jesus guys. whats with all the shotgun 'just start replacing random stuff related to cooling' diagnosis.

if you are certain its up to temp then...

its possible for the fan motors to fail, if there is a circuit being supplied to the fans (im not sure which side is switched) and they are not running then there is a good chance its poked.

sometimes giving the back of the motor a tap will make it kick into life. if this is the case you need another fan. alot of japanese cars will run the fans when you unplug the thermo fan switch. if you can confirm your switch works like this by unplugging it at a time when the fans have decided to work, and it brings them on, it might make it easier for you to trace the problem since you'll be able to be sure the fans SHOULD be operating, without needing the car to be hot.

or if you want to do it the tech forums way, ignore the above, bang some new fans in, and a couple of wiper blades, make sure you have fresh petrol, add another new sensor (why not) and hope for the best!

by **MAGN1T** » Mon Jul 04, 2011 9:58 am

If the temp sensor is at the bottom of the radiator like a lot of them are, then it's probably working normally and there's nothing wrong with it.
Changing parts randomly?, that's just for workshops and others who don't know WTF they're doing.
Find the sensor which switches the fan and take a voltage reading.

Steve

by **LEAKER** » Mon Jul 04, 2011 11:21 am

Cool thanks guys I'll try this tonight and let you know how I get on.
I don't think it will be the fans themselfs as neither of them are kicking in and they're run of the same cicuit. But when they do decide to work both of them are kicking in.

by **sergei** » Mon Jul 04, 2011 12:24 pm

+1 on disconnecting the temp switch and checking if the fans turn on consistently.

I have seen the temp switch to fail in such way that it would turn open circuit (turn on fans) intermittently, and eventually stop doing that altogether (thus closing the circuit permanently and shutting off the fans).

The standard fan system is wired in such way, that if the temp switch does not ground the relay (relay OFF) it turns ON the fans (by turning relay OFF, which has fans connected to normally connected pair of contacts, which in result turn ON the fans).

So theoretically either the temp switch is poked, or the wire from temp switch is grounded via wiring fault, or conacts on relay are fried and even if the relay is OFF the fans are not kicking in because of carbon build up on the contacts, or there is wiring fault in the fan power feed or grounding points.

P.S. where did you buy new switch from? I got one from repco and it was wrong kind (normally open, instead of normally connected).

by **LEAKER** » Mon Jul 04, 2011 1:29 pm

Had the same problem with repco but managed to source the correct one through them with a little help of a tridon catalogue.
I might try checking the earth as you say because it sounds like that could be the most likely cause from my symptoms. And the fuse. But ill take the plug off first and start wiggling things around lol

by **LEAKER** » Mon Jul 04, 2011 6:59 pm

anyone thats interested i found the problem. The main power feed to the fans had a ver coroded terminal. Wiggle it and it would work then stop (with sensor unplugged)

by **CelicaGT8** » Mon Jul 04, 2011 7:10 pm

Think its a problem with that plug a

by **CelicaGT8** » Mon Jul 04, 2011 7:10 pm

OMG your my hand twin!

by **jaypines** » Mon Jul 04, 2011 7:19 pm

LEAKER wrote:i dont run aircon. have my aircon fan hooked up to feed of my engine cooling fan and both of the fans run sometimes and then both of them dont other times.

this is probably why that connector burnt. the relay circuit for the engine cooling fan is designed for a single fan only... somethings gonna give way if youre running both fans on that circuit. its best to wire another relay for the aircon fan if you intend to run both at the same time.

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ST185 Cooling fans intermittent when hot

ST185 Cooling fans intermittent when hot

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