350i Otter Switch

[mikanel]

I am having problems with otter switches failing on my 350i, I'm on my 3rd now from different suppliers, and this one rated at 86C on and 76 off seemed ideal for the position in the top of the rad. I checked it off the car and it switched fine at 86C and off again at 80C. Initially on the car it seemed OK although the water temp was a little on the high side at about 90C, but now after a couple of weeks it has stopped working again and the fan doesn't start with the water temperature in the high 90's. The relay was working OK and would start the fan when the otter switch wires were shorted out but I replaced it in case it was getting a bit tired but with no improvement. Any suggestions please as I'm getting fed up with removing the headlamp pod to get at it.

Mike

[jp2405]

Hello Mike

I know there is a cost involved, but have you considered fitting an electrically controlled fan? You would then be able to adjust the temperature at which the fan operates. Then the otter switch becomes redundant, but can remain in situ as a plug.

John

[KKson]

Had a M22 brass boss fitted to all my three Wedge radiators and replaced otter switch with a TVR Griffith fan switch. Easy peasy and works a treat.

[phillpot]

KKson said:

Had a M22 brass boss fitted to all my three Wedge radiators and replaced otter switch with a TVR Griffith fan switch. Easy peasy and works a treat.

Another way of doing it (not saying this is the correct hose size, check!)

https://www.carbuilder.com/uk/aluminium-modular-in...

[adam quantrill]

Also Kenlowe (and probably others) do an adjustable stat with a capillary bulb, the bulb is inserted into the top hose where it's clamped.
A tenner: https://www.ebay.co.uk/itm/353227486520

Edited by adam quantrill on Wednesday 11th August 12:43

[BlueWedgy]

Adam that fleabay joby seems to be very similar to that as fitted to my 350i by the previous owner.

[ChrisW500]

Back in the days when I had a couple of 350i's I found the reason for otter failure was that the system still had air in it. it was normally towards the top of the radiator or the heater circuit. if the otter is in a air pocket it heats up faster and cooks the otter switch. There is a lot of discussion on here about how to "burp" the system, a few times and patience is sometimes required especially after you have been replacing otters or draining down the system.

Good luck

[mikanel]

Thanks for your comments, Before removing the light pod again to look at the otter switch I thought I would have one last electrical check.

I seem to be chasing bad electrical connections, as although previously checked, removing and reinserting the relay restored power to the fan connector which looked fair but a clean of the connector pins then made the fan run. I think going forward I will take up Adams suggestion and fit an adjustable stat.

The otter switch currently fitted is a Griff item with the thread machined off to suit the Wedge push fit, and in spite my initial thoughts of failure is still working. I must use the car a bit more often, it doesn't seem to like sitting in the garage.

Mike