Replacement radiator fan thermostat

[AndM]

I think I might need to replace the radiator fan thermostat as the fan isn’t coming on but runs when wired directly to battery. I have checked the wiring and power is getting through the fan down to the thermostat. A quick look shows OEM part not available but possible substitutes have only two terminals where original has three. That is power through fan, earth to earthing block on inside front wing and short wire from thermostat to collar around thermostat where it seals to radiator body. Not very familiar with electrics, can anyone tell me why the existing thermostat has two earth connections (one to earthing block and one via collar) and if I replace with a two terminal thermostat is it ok for it to earth to the earthing block alone without having an earth to a collar on the thermostat itself. Any help much appreciated.

[capriblu]

I've only ever seen two terminal fan switches on the betas that I have had? (Single earth to body mounted terminal block in front corner near headlight).  Any M22 x 1.5 radiator fan switch rated within the original 87/92 range will do the job. You can choose a lower temperature switching item if you want the fan coming on earlier.  Loads on ebay to choose from.

[Thotos]

The collar should be separate to the thermo-switch so can be transferred to the new one. It's there to earth the radiator. Before changing your radiator switch, check your water thermostat. If that's not opening, the engine will get hot but fan will not come on as the hot water is not reaching the radiator.

[Neil-yaj396]

This thread gives details of my troubles with the switches, including compatible part numbers;

http://www.betaboyz.myzen.co.uk/forum/index.php?topic=2864.0

[AndM]

Thanks for help and advice. Much appreciated. Radiator getting red hot so seems likely thermostat all ok. Confirmed fan runs when earthed to battery. Confirmed power arriving at thermo switch via fan and that both earths from thermo switch are good so looking very much like thermo switch itself. Just had radiator re-cord and was all working fine before. Will order a replacement thermo switch and test old one when I take it out. Was hoping not to have to drain down and mess about replacing but looks like that is the only option left. Thanks again for replies.

[Neil-yaj396]

I found that if you loosen up the old switch first and have the new one to hand you can swap them quickly, only losing a pint or so of coolant.

[betaveloce]

The collar should be separate to the thermo-switch so can be transferred to the new one. It's there to earth the radiator. Before changing your radiator switch, check your water thermostat. If that's not opening, the engine will get hot but fan will not come on as the hot water is not reaching the radiator.

Old topic, but it appears that the thermoswitch in my radiator also gave up. I have an HPE 2.0 i.e., so unlike in the older carburated versions, the thermoswitch in mine also has three wires, as the topic opener describes. I ordered a new old stock one, possibly the last one around, but that doesn't seem to work either. So can I replace my three wired thermoswitch by a standard two wired one? If I keep the collar, as Thotos suggests, I suppose I can just earth it separately... But why does the radiator needs to be earthed anyway, I wonder...?

[hutch6610]

Are you sure the fan is working properly before you condemn the new old stock switch? If you earth the wire with the bullet connector (which goes to the fan) it should come on, If it doesn't then you need to sort that out first.
I believe the switch was earthed to stop corrosion, some had plastic tanks.

[betaveloce]

Are you sure the fan is working properly before you condemn the new old stock switch? If you earth the wire with the bullet connector (which goes to the fan) it should come on, If it doesn't then you need to sort that out first.

Yes, fan is coming on wired like that, so I'm assuming that's fine.

I believe the switch was earthed to stop corrosion, some had plastic tanks.

Ah, that makes sense, yes, plastic in the case of my i.e.

Thanks for your response, I'll just order a two wired thermoswitch then, re-use the collar and earth that separately 

[betaveloce]

Old topic, but it appears that the thermoswitch in my radiator also gave up. I have an HPE 2.0 i.e., so unlike in the older carburated versions, the thermoswitch in mine also has three wires, as the topic opener describes. I ordered a new old stock one, possibly the last one around, but that doesn't seem to work either. So can I replace my three wired thermoswitch by a standard two wired one? If I keep the collar, as Thotos suggests, I suppose I can just earth it separately... But why does the radiator needs to be earthed anyway, I wonder...?

update: it appeared that a jammed thermostat was the culprit after all. However the NOS-switch did prove faulty as well 
Installed a new thermostat and another new switch, and now everything is okay again 
That means it's possible that the original switch was working fine, but I did not bother to put that in again as I've waisted enough coolant now 

I did try to find a thermoswitch that works with lower temperatures,, but I did not find one.

[Gromit]

Just tacking on a query to this admittedly old thread. I can buy a new Facet Italian made radiator fan switch or a NOS Sipea factory original for twice the price. Is there any point in paying twice the price for the genuine NOS version on the assumption that it might be better quality/more durable and/or reliable, or just go with the modern aftermarket replacement? I note that the last reply in this thread mentioned a failed NOS fan switch. Which suggests that it is a lottery in terms of whether what you buy will actually work reliably.
Andrew

[SanRemo78]

I wouldn't rely on the switch, it can't anticipate you sitting in traffic before it happens. I'll be fitting an over-ride switch on the dash so I can switch it on at will once the car is done!

[WestonE]

Get the new one they are not better for being older!

[JohnFol]

Override switch fitted, but can't help but think there needs to be a bit of logic in the circuit, ie if over ride on and engine off then auto turn off after 5 mins...