Club 80-90 Forums

For as long as I can remember our radiator fan hasn't been kicking in. Finally took to garage to be looked at today. He can't find out what's wrong. He's got the fan working it just isn't being triggered by the thermo switch. He's installing a manual switch for us as we have a long journey tomorrow. Any ideas?

New thermo switch? They are not expensive.

The thermo switch is all good it seems.

danmetallic wrote:The thermo switch is all good it seems.

If the fan works just fine with the thermo switch bypassed by either a jumper wire or a manual bodgeswitch, then it can ONLY be the thermoswitch at fault.

Mine is exactly the same - I have never had it on. New thermoswitch, relay checks out OK, fan works on both speeds, it just never gets hot enough to kick in. Just did a 165 mile trip to Birmingham and it still didn't come on even with our current high temps. As long as you aren't overheating I wouldn't worry about it.

My thermo switch also bypassed with a manual one which I very rarely use. The only time the temp gauge has gone past half way was after idling for half an hour on a hot day. Normally it is just below that. My thermostat is 80 C. I wouldn't worry about yours either. I suspect that fan is only needed when the engine has to work hard at low speeds e.g. going up a mountain pass

Well, we've fitted a manual switch now. Wondering if it's anything to do with the sensors then as after about 40 mins of driving in this recent heat the dash temp gauge was getting dangerously high. Only would come down after blasting the cab heaters on full (not great in these temps).

Have you checked the temp of the radiator when it has gone high? Because the thermoswitch will never come on if the hot water isn't reaching it. (waterpump dodgy,blockage or airlock)

Oldiebut goodie wrote:Have you checked the temp of the radiator when it has gone high? Because the thermoswitch will never come on if the hot water isn't reaching it. (waterpump dodgy,blockage or airlock)

No I haven't. So are you saying if the thermoswitch is good it would kick the fan in? Therefore it may be sensor etc? Ps how do you go about checking temp?

The sensor for the temperature gauge only measures the engine coolant temperature, if your circulation is poor the radiator will be be a lot cooler and therefore the fan will not operate. I use a cheapo infra-red temp measurement gadget, it doesn't matter if it isn't too accurate as what you are looking for is the difference in temp of the engine hoses to the rad. There will be a normal small difference due to the coolant losing heat on its way to the rad. I have checked my rad and it doesn't get anywhere near the temp for switching the fan on and the engine isn't running hot in the slightest.

danmetallic wrote:So are you saying if the thermoswitch is good it would kick the fan in?

That's precisely the job of the switch in the rad.

And if your temp gauge is getting high, without the fan coming on, then the switch is fubar. Assuming, of course, it's not that your rad is fubar and not allowing hot coolant to get to the switch...

'I use a cheapo infra-red temp measurement gadget, it doesn't matter if it isn't too accurate as what you are looking for is the difference in temp of the engine hoses to the rad....'
obg - i too have one of the cheapo infrared point n get the temperature 'guns' -
do you have any 'standard' temperatures on our vans ?-
the only one i know so far is - engine - warmed up - 85 to 87 degrees -
your rad once engine has warmed up? enine hoses? thermostat?
any figures - or ideas where to get these figures be much appreciated -
edoh

No, all that I remember was the rad was around 5 degrees cooler than the hoses. Every engine will be different - my figures wouldn't apply to a petrol engine nor most probably a JX or CS or whatever is there.

'all that I remember was the rad was around 5 degrees cooler than the hoses'
That's good to know -
might have a point and note day round the van - cold and warmed up - just for my own reference -
cheers

If you dont have a infra-red temp gauge then use a hand... ( be careful though ! ) feel the temp of the hoses in the engine bay, then feel the temp of the hose at the rad, or feel the top of the rad then the bottom , any difference ? remember you have 16 litres of coolant , thats a lot of water to absorb the engine heat. If I remember correctly , the fan only drops the max temp down by 10 degrees...obviously that is enough to prevent the water boiling.