how are the fans meant to work
Discussion
My fans didn't seem to kick in today (not even sure what the temp was - a different issue), but how are they meant to work? the previous owner had a fan kenlowe fitted along with a new rad, i can see two wires coming from here, one is the ground, and the other leads to the override switch. so how does the fan kick in? Is there a thermostat on the fan itself?
The fan is operated by an otter switch which is located in the top right corner of the rad, I think on the 350i there is an access hole in the side of the offside headlamp pod recess. I know on the 400SE you can feel the switch but can't actually see it. The otter switch closes energising a the fan relay which then switches the high current needed by the fan. Oh and don't forget the fuse, if the fan sticks for some reason it may have just popped the fuse.
As the otter switch is a sod to get at I'd start with the fuse / relay and work back.
As the otter switch is a sod to get at I'd start with the fuse / relay and work back.
Hi Mate...It does depend how its been modified, I much prefer it when a thermostatic controlled probe is set between the radiator fins..Then the fans set to come on just after the thermostat has opened.
Unfortunately i only have an override switch so this is the route i will be going, If your temp gauge is not working then get yourself a laser point thermometer, They come in handy..Check what temp the rad is after around 10-15mins ..I think most V8's have an 88 degree thermostat so when the rad is reaching 90 the fans should kick in, If they don't then it override only....Cheers...Ziga
Unfortunately i only have an override switch so this is the route i will be going, If your temp gauge is not working then get yourself a laser point thermometer, They come in handy..Check what temp the rad is after around 10-15mins ..I think most V8's have an 88 degree thermostat so when the rad is reaching 90 the fans should kick in, If they don't then it override only....Cheers...Ziga
If you want to test them then next time you come home let the car sit on idle until the fans kick in - should be around 95-105C on the (inaccurate) gauge. Then leave it running and the temp should pull down to around 85-90 and the fans should turn off. This cycle should then repeat.
Observe for water leaks too (much easier when sitting on the drive).
Stop the engine when satisfied and then make sure the hoses feel nice and tight and listen for any hissing. They should stay pressurised for a good 5 mins (or more) when fully hot. If not, investigate for loose clips etc.
Observe for water leaks too (much easier when sitting on the drive).
Stop the engine when satisfied and then make sure the hoses feel nice and tight and listen for any hissing. They should stay pressurised for a good 5 mins (or more) when fully hot. If not, investigate for loose clips etc.
wiring diagrams here http://www.pistonheads.com/gassing/topic.asp?t=118... extremely useful. i guess i need to find out where the override is spliced in and trace wiring back from that point to the rest of the circuit.
jindle said:
being even more paranoid i may wire in a light so i know when the fan is on
All that tells you is that the light is on, it doesn't tell you the fan is running 
Of course if you're sat in traffic you can hear the fan running, but then if you can hear the fan, why do you need a light... 
There are a few ways in which to trigger the fans...On my 280i i had a kenlowe control unit that was set to come on at a certain temperature and then the two stage boost fan would kick in if it went over the set temp.
Originally i had a capillary probe thermostat that inserted into the top hose and had a rubber sleeve that sat on the collar of the radiator so that the sensor wire could pass over it without leaking.
I prefer this type which goes into the fins of the rad.
This is something i may well invest in as all i have at the moment is an override switch...(With a light)...But i do sometimes forget to switch it on...
https://www.google.co.uk/shopping/product/77995237...
Originally i had a capillary probe thermostat that inserted into the top hose and had a rubber sleeve that sat on the collar of the radiator so that the sensor wire could pass over it without leaking.
I prefer this type which goes into the fins of the rad.
This is something i may well invest in as all i have at the moment is an override switch...(With a light)...But i do sometimes forget to switch it on...
https://www.google.co.uk/shopping/product/77995237...
V8 Fettler said:
Observe the voltmeter, although the fan motor could be stalled, thus drawing current and dropping the voltage across the voltmeter, fooling you into thinking all was well.
Cooling fans take about 10-15A when they're running; a stalled one would (one would hope) blow the fuse - or set the wiring loom alight My preferred option would be a current-sensing relay in series with the fan feed. A true paranoiac would use that to kill the ignition if the fan failed
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