Hi,
I have an old R reg astra, which over heated today as the fan didn't seem to kick in. I have checked the fuses and none are blown and are seated properly.
On the poer lead to the radiator fan there is no power when I put a multi-meter across it and also on the fuse board.
Which explains why the fan is not working.
Anyone know what I can do to get it working again ?
Thank
try shorting the pins on the switch wiring, the switch is the only regular fault.
HI mrc, thanks for the post. How would I do this (apologies not the most electrically minded) ... thats the srting the pins bit ?
so is this the electrical plug that goes in to the radistor fan I need to do this on ?
no, look at the radiator, near the bottom at one side or the other will be a lump screwed into the rad., there will be an electrical plug on that, remove it, there may be two or three pins, one will be live (should be), the other one or two go to the fan, using a paper clip connect the live to the other pin (either if there are two) the fan should run. You then have to determine if the switch is faulty or there is no hot water there! usually it is the switch. you will need the ign. on to do the above test.
I know it's mild at the moment but is it hot enough to cause the engine to overheat if it's just the fan not working? Isn't it more likely to be the engine thermostat or water pump?
To find out run the engine and feel the hoses. The top hose to the radiator should get hot when the engine heats up and the radiator should also get hot.
Overheating in traffic is almost invariably caused by the fan not coming on, irrespective of the ambient temperature. Over about 30, the fan very rarely cuts in. I did have a car once that was cool in traffic, but overheated as it got over 60, but that turned out to be due to a previous owner pressure washing the radiator and blowing all the fins off.
I have a car like that at present, loads of the fins have fallen off, but still fine for local journeys. I must get round to changing it.....mutter, mutter.
The switch is on the negative side and the fan will only run with the ignition switched on. If the plug on the thermal switch has fallen off or the switch is faulty or the wiring is faulty on the earthy side of the fan connector (or indeed on the battery side) then you won't see any voltage across the fan.
Turn the ignition on, pull the fan connector off, measure the volts from each of the terminals direct to battery earth. If you see battery volts then reconnect the fan connector and provide a temporary earth from the terminal you didn't see volts on to a suitable place on the bodywork (under a wing bolt for instance)
This will get the fan running continuously when the ignition is switched on - if the battery and thermostat is in good condition a car can run like this no problem for ages, its just a bit noisy - probably not a good idea if the weather gets towards freezing.
The thermal switches are a sod to get to as the top hose or air filter box usually gets in the way. With a cold engine and small hands you might just be able to unlatch the connector, there is only one lug to lift. If you can do this, then remove your previously applied short and short the two terminals out you can now see on the thermal switch connector. The fan should run. If it doesn't it's a wiring problem between the fan and the thermal switch connector or the thermal switch connector and its earth.
The thermal switches come in three types. Some of the aftermarket ones (I can't recall the make, but what you'd get at a factors or a motorists discount shop) list the wrong type even when you have the right VIN number. The housing and pins look right with a quick glance and the connector will still fit, but the pins are in the wrong position so the switch will do bugger all. I know Unipart used to supply the correct ones with the right temperature setting but unless you find one in a scrapyard its best to take the original one with you when you buy a replacement.
You'll need something like a 32mm spanner for the nut - it's pretty big and there is bugger all space to fit a socket or adjustables.
IIRC all the fans in that era are low side switched so there will be no, or very low volts on the terminals given the impedance of the fan motor.
Brain fart moment there, make that no or very low volts on the terminals, sod the fan!
earth - thermal switch - fan - fan fuse - ignition relay - battery
"Themonk" wrote
I once had a fan not work problem. The fan sensor is at the bottom of the radiator whereas the warning light is at the top of the engine. On this occasion radiator blockage raised the top/bottom temperature differential so the the fan sensor couldn't see the overheating.
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