thermoswitch

[mongoose]

could anyone help with the following please:-id like to fit an in-line thermowitch to the outlet hose from the radiator on my car(griff 500).its easy enough to buy the housing from demon tweeks etc,but the thread sizes in the housing are either 3/8bsp or 5/8unf.in these thread sizes the lowest cut in temp switch i have so far found is 92oc(dihatsu i think).id like a cut in temp of 85-88oc.does anybody know which switch i need?-thanks-mv

[grahambell]

You can get adjustable thermo switches which are basically the same as on your central heating system.

Try asking NF Auto Developments, who besides making Ferrari P4 replicas sell all sort of component parts. See www.nfauto.co.uk

[mongoose]

firstly thanks graham for the recommendation,have tried them but they couldnt help on this occasion.what id also like to ask anyone out there is why have some thermoswitches got 3 connection pins instead of 2? is it a two stage cut in or something.the reason i ask is that looking for 3 pin thermoswitches may give me more options on temperature.thanks-mv

[grahambell]

In that case you could try Merlin Motorsport or Europa, both of which are almost certain to be at the Stoneleigh kit car show this Sunday/Monday, along with a whole load of other companies. Might be worth a visit?

Can't help with the 2 pin/3 pin thing.

[david beer]

The three pin ones i use are only one common, one normally open contact and one normally closed. I believe all will be the same.

[GreenV8S]

The bottom hose is definitely the right place to fit it, but it's worth remembering it runs cooler than the top hose so you will need an even lower temperature switch. In my experience the bottom hose is typically up to 10 deg C cooler than the top hose, so 90 deg switch in the top hose is roughly equivalent to 80 deg in the bottom hose. You might want to set it cooler than this, since the bottom hose temperature is a much better indication of when you need the fans on, and it will normally be below 60 deg if there is enough air flow. As a starting point, I have my mod-wise fan controller in the bottom hose set to bring the fans on full at 70 deg. This will probably vary between cars depending on air flow characteristics etc but is a rough guide.

[geoffric]

Yes there is such a thing as a three pin thermoswitch. I use one from a VW Passat in my MG V8. Fits an M22 thread and provides two thermoswitches with a common ground - one switch is the correct range for engine cooling fan and the other operates at a higher range. I just use the second as a failsafe on the first but I guess I could have used it to switch in the second of a pair of cooling fans when the engine reached a higher temp.