where is automatic radiator cooling fan switch?
Discussion
on the 1984 350i i have just bought, with 3905 nck motor running a holley carb and offenhauser manifold, the twin electric cooling fans on the back of the radiator come on with an obviously non=standard manual toggle switch under the dash, but not on their own due to engine temp. i let it run up to 95 on tvr temp guage and fans didn't come on until i switched them on. i cannot find a sensor or switch on the engine other than the temp guage sender in the front of the inlet manifold. does that also operate the auto fan switch or should it have another sensor/switch and if so where is it in the engine bay/ hard to follow the fan wiring as it is so hard to access/see that far forward in engine bay.
The temperature sender switch only sends signal to the temperature gauge and only has one wire. The electric fan should have an otter switch on the top part of radiator and is usually found on drivers side with two wires. It is difficult to get to and I believe the headlight needs to be removed to gain access. This is what switches the fan on automatically and is bypassed by a switch to operate manually.
Tony. TCB.
Tony. TCB.
ahhhh thanks tony, that explains why i couldn't see it on the engine!!! bugger, gonna have to do more digging about ten to check that switch and wiring, cheers
ElvisWedgely said:
The temperature sender switch only sends signal to the temperature gauge and only has one wire. The electric fan should have an otter switch on the top part of radiator and is usually found on drivers side with two wires. It is difficult to get to and I believe the headlight needs to be removed to gain access. This is what switches the fan on automatically and is bypassed by a switch to operate manually.
Tony. TCB.
Tony. TCB.
KKson said:
Otter switch on my 350i is top of radiator, on the side, and on the near side (passenger side) you can only see it with the bonnet off or headlamp pod removed. I've now replaced both Wedge otter switches with soldered boss and Griff M22 threaded fan switch.
Yes, Keith is right. Otter switch is on passenger side not drivers side. Sorry, my mistake.Tony. TCB.
hi, when you say 'both wedge otter switches' do you mean your wedge 9and so maybe mine) has two otter switches or that you have two wedges and you have done both? if the former what is the 2nd for? cheers
KKson said:
Otter switch on my 350i is top of radiator, on the side, and on the near side (passenger side) you can only see it with the bonnet off or headlamp pod removed. I've now replaced both Wedge otter switches with soldered boss and Griff M22 threaded fan switch.
thanks again wedg1e, that sounds like a good plan!
Wedg1e said:
The thermoswitch was in the top left of my (ex-Rangey) radiator on the 390SE, I had it blanked off completely as the car uses a Kenlowe 'stat with sensor in the top hose with a dash over-ride switch. One of these days I'll fit fan failure warning to it as well...
drak ula said:
on the 1984 350i i have just bought, with 3905 nck motor running a holley carb and offenhauser manifold, the twin electric cooling fans on the back of the radiator come on with an obviously non=standard manual toggle switch under the dash, but not on their own due to engine temp. i let it run up to 95 on tvr temp guage and fans didn't come on until i switched them on. i cannot find a sensor or switch on the engine other than the temp guage sender in the front of the inlet manifold. does that also operate the auto fan switch or should it have another sensor/switch and if so where is it in the engine bay/ hard to follow the fan wiring as it is so hard to access/see that far forward in engine bay.
It's not a 350i then! 
funny you should say that poledriver, was thinking of picking the stickers off yesterday after washing it. starting with the i but maybe even the 50 too as it's really a 390 so even though they did make a handful of 350s with the 3905 before calling it the 390, i think it might be an idea to remove the whole 350i as it really is a mongrel? and i can't call it an se as it doesn't have an lsd YET ;-)
http://www.pistonheads.com/tvr/wedges/se.htm
http://www.pistonheads.com/gassing/imgs/4.gif It's not a 350i then!
http://www.pistonheads.com/tvr/wedges/se.htm
http://www.pistonheads.com/gassing/imgs/4.gif
PoleDriver said:
It's not a 350i then! adam quantrill said:
Otter switch is on the nearside before you remove the wrong headlamp pod.
Im pretty sure mine was on the O/S?....I had mine welded up and was going to use a thermostatic housing or something similar to what i had on the 280i...http://www.carbuildersolutions.com/uk/adjustable-f...
Although i wouldn't use PTFE...Much better with the correct seal...(If i can find it)...I was going to fit something like this on the 350i but i have a manual override only and just keep an eye on it...
http://www.holden.co.uk/displayproduct.asp?sg=1&am...
You may think that that is a bit of a chancers way but i know by keeping an eye on the gauge when to turn it on, I also know how long to keep it on for..Infact just recently i noticed it wasn't taking the temp down so pulled over and found this...
The wire at the battery end accidentally got stretch after a master cylinder replacement.
I have since soldered up some proper wire and fittings....
Im sure you know already but just in case, The temperature switch should always go "Hot side" of the engine..Or pre-rad..Post thermostat...
thanks again, i didn't know, it didn't occur to me but now you have said it, it seems obvious. cheers
mrzigazaga said:
Im pretty sure mine was on the O/S?....I had mine welded up and was going to use a thermostatic housing or something similar to what i had on the 280i...
http://www.carbuildersolutions.com/uk/adjustable-f...
Although i wouldn't use PTFE...Much better with the correct seal...(If i can find it)...I was going to fit something like this on the 350i but i have a manual override only and just keep an eye on it...
http://www.holden.co.uk/displayproduct.asp?sg=1&am...
You may think that that is a bit of a chancers way but i know by keeping an eye on the gauge when to turn it on, I also know how long to keep it on for..Infact just recently i noticed it wasn't taking the temp down so pulled over and found this...
The wire at the battery end accidentally got stretch after a master cylinder replacement.
I have since soldered up some proper wire and fittings....
Im sure you know already but just in case, The temperature switch should always go "Hot side" of the engine..Or pre-rad..Post thermostat...
http://www.carbuildersolutions.com/uk/adjustable-f...
Although i wouldn't use PTFE...Much better with the correct seal...(If i can find it)...I was going to fit something like this on the 350i but i have a manual override only and just keep an eye on it...
http://www.holden.co.uk/displayproduct.asp?sg=1&am...
You may think that that is a bit of a chancers way but i know by keeping an eye on the gauge when to turn it on, I also know how long to keep it on for..Infact just recently i noticed it wasn't taking the temp down so pulled over and found this...
The wire at the battery end accidentally got stretch after a master cylinder replacement.
I have since soldered up some proper wire and fittings....
Im sure you know already but just in case, The temperature switch should always go "Hot side" of the engine..Or pre-rad..Post thermostat...
thanks, is the kenlowe thermostst switch the kind that is just pressed against the outside of a pipe or the rad or something that is actually plumbed in and into the coolant?
adam quantrill said:
Otter switch is on the nearside before you remove the wrong headlamp pod.
Don't poke it though. If it isn't working just remove the wires and ket a kenlowe thermostat switch instead - you can adjust this to suit.
Don't poke it though. If it isn't working just remove the wires and ket a kenlowe thermostat switch instead - you can adjust this to suit.
how about something like this, i reckon this could be fitted somewhere nice and accessible in the engine bay nearer the engine, what do you think?
http://www.ebay.co.uk/itm/38MM-LAND-ROVER-DISCOVER...
http://www.ebay.co.uk/itm/38MM-LAND-ROVER-DISCOVER...
Kenlowe are just one maker of this type of thermostat and to a degree the name bumps the price up; essentially it's the same sort of thing used in freezers at one end of the temperature spectrum and ovens at the other.
You have an adjustable dial that presets a spring-loaded switch and a copper capillary tube with a sensing element on the end of it... this may be as much as a metre away from the switch end - any spare capillary can be coiled up carefully and tie-wrapped out of the way.
In the typical Kenlowe application the sensing head is located in the top radiator hose; they supply a piece of shaped rubber that creates a seal around the capillary when you tighten the hose clip.
Once the sensing element detects the water temperature exceeding the setting of the switch it closes and fires up the fan.
The switch contacts are typically rated for 10A DC but this is really a bit marginal for a decent electric fan which might yank 30A start-up current and even as much as 15A when running. The 'proper' way is to use the Kenlowe switch in place of the original 'Otter', so the switch turns on the car's own fan relays. Thus the only current flowing through the thermostat contacts is the trifling few milliamps needed to power the fan relay coil. Switching the fan motor directly runs the risk of the thermostat contatcs arcing and burning out, costing £££ to replace the whole unit rather than the couple of quid to replace the fan relay if the same thing happens to it.
As I said, you don't have to use a Kenlowe; you just need the same type of 'stat with a suitable temperature range (say 70-100 degrees, though they usually have wider bands than that) - a 300 degree oven 'stat would be a bit coarse in adjustment but would still work.
You have an adjustable dial that presets a spring-loaded switch and a copper capillary tube with a sensing element on the end of it... this may be as much as a metre away from the switch end - any spare capillary can be coiled up carefully and tie-wrapped out of the way.
In the typical Kenlowe application the sensing head is located in the top radiator hose; they supply a piece of shaped rubber that creates a seal around the capillary when you tighten the hose clip.
Once the sensing element detects the water temperature exceeding the setting of the switch it closes and fires up the fan.
The switch contacts are typically rated for 10A DC but this is really a bit marginal for a decent electric fan which might yank 30A start-up current and even as much as 15A when running. The 'proper' way is to use the Kenlowe switch in place of the original 'Otter', so the switch turns on the car's own fan relays. Thus the only current flowing through the thermostat contacts is the trifling few milliamps needed to power the fan relay coil. Switching the fan motor directly runs the risk of the thermostat contatcs arcing and burning out, costing £££ to replace the whole unit rather than the couple of quid to replace the fan relay if the same thing happens to it.
As I said, you don't have to use a Kenlowe; you just need the same type of 'stat with a suitable temperature range (say 70-100 degrees, though they usually have wider bands than that) - a 300 degree oven 'stat would be a bit coarse in adjustment but would still work.
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