Fan not coming on

[julians]

I've just got back from holiday for two weeks, and went for a quick drive of the car and I noticed a slight problem.

 

The water temp started to climb past its normal running temp, so I had a quick look and noticed that the fan wasnt coming on. The fan is controlled by a thermostat ( rather than the ecu), so I shorted the two wires together and the fan came on, so no problems with the power supply to the fan. I then presumed the thermostat must be broken, so I replaced it with another one I had lying around which I know works. but the fan still didnt come on. At the moment I am driving with the fan shorted so that it is on all the time.

 

Does anyone know what the problem may be. It was working fine before I went on holiday ( fan should come on at around 86 degrees)

[Swiss_Tony]

Have you checked for air locks? (especially k series)

It may be worth changing the rad cap.

Have you checked the gauge is working correctly?

I assume this happens when you are stationary.

 

James

 

 

 

[CHRIS CLARK]

This stat. that was, err, lying around. How do you know it works, and at the correct temp?

 

I proved mine was not working correctly by connecting some wiring to a couple of female spade connectors. This was in turn connected at one end to the stat and to a multi meter at the other (set for continuity test---mine has a buzzer). The stat was then dangled over/in some v. hot water (from the micro wave). TAKE CARE etc etc.

This showed that the unit was kaput ie it the buzzer didn't go off.

When tried with a 'Kenlowe' adjustable stat mechanism (adjustable from 60* to 130*) it all worked fine!!!

 

Guess what's fitted to my Seven now?

[Tin Man]

Julians

 

I had this problem, It turned out to be a bad earth from the sender giving me a very high reading. Take It out & give It a good clean. If It`s not the sender then it will probably an air lock. Does the bottom of the radiator get hot?

 

 

[Red SLR]

Julian, is this on your new engine?

 

If so I suggest youmake sure there is no air in the system, it took me over 2 hours to bleed it all out of my engine after I converted it to throttle boddies.

 

I also had to replace the stat, I think the high temp of the air and water had broken it.

 

X777CAT

[julians]

I thought it may be air trapped in the system, but then I dont know why it shoudl show these symptoms after sitting for two weeks, remember it was fine before I went on holiday.

 

I'll try the old multimeter and boiling water routine on both stats to see what happens.

[ashaughnessy]

Could I borrow this thread for a moment? In answer to the original question, if you've lost lots of water from the system it might be that the fan switch isn't actually sitting in any water? I've noticed that in the past on my car. Which leads on to my own question. My 1700 SuperSprint is overheating. It loses a lot of water after a long motorway journey. Just got a new radiator (old one pretty tatty), new filler neck (old one possibly losing pressure and therefore water), new filler cap. On the way home after picking it up, a 3 hour motorway journey, it started out showing (IMHO) a healthy 78 degrees. After a while, it started to creep up. After about an hour or so, it was showing 90 degrees. I pulled into some services and before I could park the gauge was into the red at well over 100 degrees. The fan was on, by the way. Once it cooled down, it took a significant amount of water.

There's some suspicion that the thermostat isn't working correctly. I was told that normal operating temperature should be about 90 degrees - it's always been about 78 degrees in the past, so perhaps the thermostat isn't opening properly and is sticking somewhere? Also, because I lose water, perhaps I have an airlock. How do I get rid of it if I have? I go to great lengths to get as much water in as I can - I always jack up the front then the rear to dislodge bubbles. What else can I try?

[V7 SLR]

Beware talking about the thermostat and the fan switch. Two different pieces of kit. Stats generally work OK, and are sited under the throttle towards the front of the engine, whilst the fan switch is normally sited in the rad, or the pipework very close to the rad.

 

I've seen quite a few fan switches fail on K's now. Some people, having replaced the switch a number of times (very definately plural) resort to placing an override switch on the dash. If you don't have a heater you can use the heater-fan switch for this. Very neat.

 

I know of a letter that's been fired off to Jez Coates today advising about this problem (amongst a few other repeated failures, like K series starter motors). I'll be monitoring any response and will advise.

[julians]

I meant fan switch, I tried the boiling water and multimeter routine last night and proved that boths switches are broken, so I'll be off the halfords for a replacement soon.

 

[CHRIS CLARK]

Well at least it has proved the point as to where your problem is.

 

 

(PS. I don't trust bits lying around as they were probably removed 'cos they were U/S in the first place!!!)

[Mick Day]

After the last thermoswitch failure (of many) I wired up the ECU (GEMS) to switch the fan. In the long term this should prove more reliable (I've still kept the override switch just in case).

My 2 year old starter (new type) is showing signs of not wanting to play once nice & hot. Will be very interested to hear what Jez Coates has to say.

Mick

[millsn]

Have you checked that the thermostat allows some water past itself to the rad? I.e. it should have a small hole in its circumference to allow this. Without it in normal running you get very odd behaviour. It may be that your new thermostat does not have this hole and thus you get very little circulation. You need the circulation to allow the switch to see hot water and open. I've never had trouble bleeding my old xflow so I doubt that's your problem. Don't have a blown head gasket do you? compression check?

 

Nigel Mills - 2.0 Zetec carbs

[mikehoile]

Hi Julians

Just had the same problem whilst touring in france - mines a 2001 k and the faulty switch is a VW item -- it seems that caterham have had a few faulty units. I now have an overide switch. Had the stat removed by a rover dealer in france (couldn't get at it with my limited tool kit whilst away and special tool required to get at the bolts)on the advice of caterham although the dealer didn't like this action. now had a new stat fitted as engine temp not sufficient without one.

Mike Hoile (Maidenhead)