Otter Switch for Fan

leylandracer · Post by **leylandracer** » Sat Mar 17, 2012 10:08 pm

Just looking at this topic, im having the same problem, New switch fitted but not working, if i bridge the connector the fan will come on, Mine is fitted into a hard pipe between the thermo and rad, what interested me was "The swirl pot isn't mounted on rubber mounts is it?

That would be good enough to lose the earth connection." the pipe on mine is mounted on rubber P clips so there isnt a direct contact with the chassis? Would this cause a problem?

Thanks

mgbv8 · Post by **mgbv8** » Sun Mar 18, 2012 10:08 pm

leylandracer wrote:Just looking at this topic, im having the same problem, New switch fitted but not working, if i bridge the connector the fan will come on, Mine is fitted into a hard pipe between the thermo and rad, what interested me was "The swirl pot isn't mounted on rubber mounts is it?

That would be good enough to lose the earth connection." the pipe on mine is mounted on rubber P clips so there isnt a direct contact with the chassis? Would this cause a problem?

Thanks

If you are using a switch that makes its circuit to earth through its body then having it cut into a hose will stop it working unless you run an earth wire from the housing to a chassis earth point.

I've had 3 guys at the race track in the last 2 years with the same problem on new builds. I quite like the look on their faces when I come over with a jump lead and they get fans running or in one case oil temp gauge working

leylandracer · Post by **leylandracer** » Mon Mar 19, 2012 8:42 am

The coolant set-up is more or less standard apart from the rubber lined P Clips, speaking to a auto electrician freind the other day he reckons ((without seeing it to verify), your switch will just be joining a wire together via a thermal contact, therefore does not need an earth etc. It has two wires, & these just make contact. If you join these two & the fan runs, everything you need is there, just the switch is not connecting)

Any ideas

Dont know if the pics help, you can see the switch on the 1st pic.
Thanks

leylandracer · Post by **leylandracer** » Mon Mar 19, 2012 9:25 am

Another pic

flipping thing... its really doing my head in now

DaveEFI · Post by **DaveEFI** » Mon Mar 19, 2012 9:35 am

If bridging the switch contacts makes the fan run, then either the stitch is faulty or not getting hot enough to make. There can't be any other reason.
So remove the switch and try it in boiling water. If it is ok, have you measured the temperature of the swirl pot? Could be perhaps an airlock somewhere?

richardpope50 · Post by **richardpope50** » Mon Mar 19, 2012 1:22 pm

I eventually tried my new one in boiling water and it worked just fine. I am now wondering if it was simply because the engine (water) did not get hot enough and my gauge was very inaccurate.

My car is all stripped down at the moment so in a few months (or so!) when it is back together again I'll see if it works in the car. It is obviously a simple problem!

DaveEFI · Post by **DaveEFI** » Mon Mar 19, 2012 2:18 pm

The coolant where the gauge sensor is could well be at a different temperature to where the fan switch is?

leylandracer · Post by **leylandracer** » Mon Mar 19, 2012 3:01 pm

Just bought one of these

for the hard pipe, between the thermo & fan switch, + it will give me somwhere to bleed the system.
(Small direct mount liquid filled water temp gauge. Measures 1-1/2" diameter, 3/8" NPT Fitting with 1" Probe.)

bodger · Post by **bodger** » Tue Mar 20, 2012 11:29 am

This is what i used on my V8 .....

http://www.ebay.co.uk/itm/35MM-HOSE-ADA ... 1c24e91fcf

richardpope50 · Post by **richardpope50** » Thu Mar 22, 2012 4:26 pm

DaveEFI wrote:The coolant where the gauge sensor is could well be at a different temperature to where the fan switch is?

Agreed. My Otter switch is in the swirl pot about 40cm of silicon pipe from block exit whilst my gauge is off usual temp sender. IIRC the gauge was well over 100 and on the way to 110. To me that's too high assuming it is accurate - a CAI unit.

I'm just wondering if I need a lower Otter switch setting or probably try and get an accurate temp reading first, I suppose.

leylandracer · Post by **leylandracer** » Sun Apr 08, 2012 6:12 pm

The gauge is now fitted to the top hose (Hard pipe) if only my in car Smiths gauge was as acurate, the fan switch is fine, fan coming on when it should, Just need to find out why the Smiths gauge is over reading now