I have a latish model radiator with the big screw in thermo switch in the bottom. Anyone know what temperature these are supposed to close at? Just tried testing mine in boiling water and it wouldn't fire. Held the base directly on a gas flame for about 15-20 seconds before it finally closed. A little too late for a cooling system methinks, not sure if it's faulty or just supposed to get really hot before triggering.

What are the other options for triggering an electric fan....is there a switch available that would fit the thermostat housing with sensor hole? A common replacement for the minispares switch? I could just get a replacement from minispares but that's a long wait and lot of money for something that may be no different.

Could also investigate an in-hose solution. Any ideas welcome.

most come on around 85-92c in jap cars.

I would go to Repo and have a look in there spares book and pick one with the correct thread and temp.

The usually have the temp stamped on it some where

If you need a gas flame it to make it work then its mostly stuffed.

If you think 92c is high you have to remember for every 1lb of pressure you get 1 degree increase in boiling temp

All you need to do to make a bypass is to ground the switch

Ta

Kiwiinwgtn

The ones on the SPI minis come on at 102 deg and turn off at 94 deg.
Cheers Pete

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A recent study found the average Aussie walks about 900 miles a year
Another study found Aussies drink, on average, 22 gallons of alcohol a year
That means, on average, Australians get about 41 miles per gallon

Kind of makes you proud to be an AUSSIE

That's kinda high?!

I think this one is definitely closing late - I looked a little closer and it's 92/82. So if it's not coming on after sitting in boiling water for a minute then it's taking too long for the heat to soak to the sensor anyway....so is not an accurate 92.

I was thinking about it's placement, and I think it's just plain bad design. Having the fan trigger at the radiator outlet seems a bit odd. If it DID open at 92, what's the temperature differential between the bottom and top of the radiator? The temp coming out of the head may already be 100 or more, so the oil is what....120? and that's just to turn the fan on....

I found a Trident part number for this sensor, so will probably get another one just to test. However I am tempted just to replace the whole idea with an after market controller. Davies Craig are about $75 but a little primitive. A proper job about $100......

Pressurised water boils at over 100°C, and with coolant in there that number increases again.

Fiat and Alfa ones years ago closed the circuit at 99C, so these high temps are pretty typical for thermo switches.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

The reason for the high temp is so you get a better burn with unleaded fuel.

_________________
A recent study found the average Aussie walks about 900 miles a year
Another study found Aussies drink, on average, 22 gallons of alcohol a year
That means, on average, Australians get about 41 miles per gallon

Kind of makes you proud to be an AUSSIE

The colder water is in the bottom of the radiator, so the temp sender in the the correct place as you are interested in the temp coming out of the rade and its possibly the safest place so it won't get broken

I would just find a sender with a cooler range if you want to change the range.

The fan should only really turn on when the car is stationery or after a long run and in traffic.

The Davies Craig set up does not give you degree by degree adjustabilty which is what you are chasing.

If you are clever there are a few circuits about that can does this for you

A buddy of mine played around with this for his turbo and used only one setting and the override function, which is an exspensive switch

Kiwiinwgtn

Ya I know about running temperatures, I'm saying having the fan control at the end of the water circuit doesn't appear to be the best way of achieving those temps. The water temp at the radiator outlet is effected by so many variables: ambient temperature, condition of radiator, car speed etc, whereas it's the temp of the engine you're trying to keep optimal. Maybe I'm just over complicating things....

If an't broke don't fix it

Well yees....trouble is I think it's broke

Reason I had a thermo fan (only) in the first place was because the fan shroud attached to the inner guard and most of the inner guard in my car is long gone, from when it was a track car. I think for now I'll just bite the bullet and go back to mechanical fan. I have a couple shrouds and fans, I just need to knock up a top bracket and somehow make a shroud to go between radiator and inner guard.

oh..

You need a good shroud etc to direct the air etc.

Can you not make a bolt in one.

Ya I'll knock something up, I have some galv sheet here....somewhere...and some rubber sheet to fill the gap.

For the top bracket, I figure I just make the measurement right to make the radiator vertical, but can anyone tell me this measurement in green below for a 1275 round nose bracket? (credit to JAK355 for the borrowed image)

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Also this is only the secondary fan to assist the mechanical one when you're stuck in traffic idling for a long time without much air flow.

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Hi

2 7/8 is the green measurement on my bracket

TA

Kiwiinwgtn